一个简单的spring hello world：
public class App {
public static void main(String[] args) {
ApplicationContext context = new FileSystemXmlApplicationContext("src/main/resources/spring.xml");
Person person = ((Person) context.getBean("person"));
person.say();
person.myBook();
Book book = ((Book) context.getBean("book"));
System.out.println(book.toString());
}
}
12
1
public class App {
2
3
public static void main(String[] args) {
4
ApplicationContext context = new FileSystemXmlApplicationContext("src/main/resources/spring.xml");
5
Person person = ((Person) context.getBean("person"));
6
person.say();
7
person.myBook();
8
Book book = ((Book) context.getBean("book"));
9
System.out.println(book.toString());
10
}
11
12
}
首先进入 FileSystemXmlApplicationContext 的构造方法，
可以看到该构造方法被重载了，可以传递 configLocation 数组，也就是说，可以传递过个配置文件的地址。默认刷新为true，parent 容器为null。
进入另一个构造器：
/**
* Create a new FileSystemXmlApplicationContext with the given parent,
* loading the definitions from the given XML files.
* @param configLocations array of file paths
* @param refresh whether to automatically refresh the context,
* loading all bean definitions and creating all singletons.
* Alternatively, call refresh manually after further configuring the context.
* @param parent the parent context
* @throws BeansException if context creation failed
* @see #refresh()
*/
public FileSystemXmlApplicationContext(
String[] configLocations, boolean refresh, @Nullable ApplicationContext parent)
throws BeansException {
super(parent);
setConfigLocations(configLocations);
if (refresh) {
refresh();
}
}
21
1
/**
2
* Create a new FileSystemXmlApplicationContext with the given parent,
3
* loading the definitions from the given XML files.
4
* @param configLocations array of file paths
5
* @param refresh whether to automatically refresh the context,
6
* loading all bean definitions and creating all singletons.
7
* Alternatively, call refresh manually after further configuring the context.
8
* @param parent the parent context
9
* @throws BeansException if context creation failed
10
* @see #refresh()
11
*/
12
public FileSystemXmlApplicationContext(
13
String[] configLocations, boolean refresh, ApplicationContext parent)
14
throws BeansException {
15
16
super(parent);
17
setConfigLocations(configLocations);
18
if (refresh) {
19
refresh();
20
}
21
}
该构造器做了两件事情，一是设置配置文件，二是刷新容器。
其中最重要的就是刷新配置文件refresh()，进入该方法，
refresh()方法其实是FileSystemXmlApplicationContext 的父类 AbstractApplicationContext 的refresh()方法。
@Override
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
// 为刷新准备应用上下文
// Prepare this context for refreshing.
prepareRefresh();
// 告诉子类刷新内部bean工厂，即在子类中启动refreshBeanFactory()的地方----创建bean工厂，根据配置文件生成bean定义
// Tell the subclass to refresh the internal bean factory.
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// 在这个上下文中使用bean工厂
// Prepare the bean factory for use in this context.
prepareBeanFactory(beanFactory);
try {
// 设置BeanFactory的后置处理器
// Allows post-processing of the bean factory in context subclasses.
postProcessBeanFactory(beanFactory);
// 调用BeanFactory的后处理器，这些后处理器是在Bean定义中向容器注册的
// Invoke factory processors registered as beans in the context.
invokeBeanFactoryPostProcessors(beanFactory);
// 注册Bean的后处理器，在Bean创建过程中调用
// Register bean processors that intercept bean creation.
registerBeanPostProcessors(beanFactory);
//对上下文的消息源进行初始化
// Initialize message source for this context.
initMessageSource();
// 初始化上下文中的事件机制
// Initialize event multicaster for this context.
initApplicationEventMulticaster();
// 初始化其他的特殊Bean
// Initialize other special beans in specific context subclasses.
onRefresh();
// 检查监听Bean并且将这些Bean向容器注册
// Check for listener beans and register them.
registerListeners();
// 实例化所有的（non-lazy-init）单件
// Instantiate all remaining (non-lazy-init) singletons.
finishBeanFactoryInitialization(beanFactory);
// 发布容器事件，结束refresh过程
// Last step: publish corresponding event.
finishRefresh();
}
catch (BeansException ex) {
if (logger.isWarnEnabled()) {
logger.warn("Exception encountered during context initialization - " +
"cancelling refresh attempt: " + ex);
}
// 为防止bean资源占用，在异常处理中，销毁已经在前面过程中生成的单件bean
// Destroy already created singletons to avoid dangling resources.
destroyBeans();
// 重置“active”标志
// Reset 'active' flag.
cancelRefresh(ex);
// Propagate exception to caller.
throw ex;
}
finally {
// Reset common introspection caches in Spring's core, since we
// might not ever need metadata for singleton beans anymore...
resetCommonCaches();
}
}
}
78
1
2
public void refresh() throws BeansException, IllegalStateException {
3
synchronized (this.startupShutdownMonitor) {
4
// 为刷新准备应用上下文
5
// Prepare this context for refreshing.
6
prepareRefresh();
7
8
// 告诉子类刷新内部bean工厂，即在子类中启动refreshBeanFactory()的地方----创建bean工厂，根据配置文件生成bean定义
9
// Tell the subclass to refresh the internal bean factory.
10
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
11
12
// 在这个上下文中使用bean工厂
13
// Prepare the bean factory for use in this context.
14
prepareBeanFactory(beanFactory);
15
16
try {
17
// 设置BeanFactory的后置处理器
18
// Allows post-processing of the bean factory in context subclasses.
19
postProcessBeanFactory(beanFactory);
20
21
// 调用BeanFactory的后处理器，这些后处理器是在Bean定义中向容器注册的
22
// Invoke factory processors registered as beans in the context.
23
invokeBeanFactoryPostProcessors(beanFactory);
24
25
// 注册Bean的后处理器，在Bean创建过程中调用
26
// Register bean processors that intercept bean creation.
27
registerBeanPostProcessors(beanFactory);
28
29
//对上下文的消息源进行初始化
30
// Initialize message source for this context.
31
initMessageSource();
32
33
// 初始化上下文中的事件机制
34
// Initialize event multicaster for this context.
35
initApplicationEventMulticaster();
36
37
// 初始化其他的特殊Bean
38
// Initialize other special beans in specific context subclasses.
39
onRefresh();
40
41
// 检查监听Bean并且将这些Bean向容器注册
42
// Check for listener beans and register them.
43
registerListeners();
44
45
// 实例化所有的（non-lazy-init）单件
46
// Instantiate all remaining (non-lazy-init) singletons.
47
finishBeanFactoryInitialization(beanFactory);
48
49
// 发布容器事件，结束refresh过程
50
// Last step: publish corresponding event.
51
finishRefresh();
52
}
53
54
catch (BeansException ex) {
55
if (logger.isWarnEnabled()) {
56
logger.warn("Exception encountered during context initialization - " +
57
"cancelling refresh attempt: " + ex);
58
}
59
60
// 为防止bean资源占用，在异常处理中，销毁已经在前面过程中生成的单件bean
61
// Destroy already created singletons to avoid dangling resources.
62
destroyBeans();
63
64
// 重置“active”标志
65
// Reset 'active' flag.
66
cancelRefresh(ex);
67
68
// Propagate exception to caller.
69
throw ex;
70
}
71
72
finally {
73
// Reset common introspection caches in Spring's core, since we
74
// might not ever need metadata for singleton beans anymore...
75
resetCommonCaches();
76
}
77
}
78
}
AbstractApplicationContext 的refresh()方法就是整个IOC容器初始化的所有逻辑，该方法大概做了三件事：1、构建BeanFactory 2、构建bean实例并注入相关依赖 3、触发监听
获取BeanFactory
构建BeanFactory就是其中ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();这句代码，也就是AbstractApplicationContext的obtainFreshBeanFactory()方法，从字面上来理解也是获取新的BeanFactory。
AbstractApplicationContext的obtainFreshBeanFactory()方法的第一句代码就是refreshBeanFactory()，refreshBeanFactory()是AbstractApplicationContext的模板方法，进入它的实现AbstractRefreshableApplicationContext里面，其实现代码如下：
/**
* This implementation performs an actual refresh of this context's underlying
* bean factory, shutting down the previous bean factory (if any) and
* initializing a fresh bean factory for the next phase of the context's lifecycle.
*/
@Override
protected final void refreshBeanFactory() throws BeansException {
if (hasBeanFactory()) {
// 如果存在就销毁
destroyBeans();
closeBeanFactory();
}
try {
// new DefaultListableBeanFactory(getInternalParentBeanFactory())
DefaultListableBeanFactory beanFactory = createBeanFactory();
// 设置序列化
beanFactory.setSerializationId(getId());
// 定制的BeanFactory
customizeBeanFactory(beanFactory);
// 使用BeanFactory加载bean定义 AbstractXmlApplicationContext
loadBeanDefinitions(beanFactory);
synchronized (this.beanFactoryMonitor) {
this.beanFactory = beanFactory;
}
}
catch (IOException ex) {
throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
}
}
29
1
/**
2
* This implementation performs an actual refresh of this context's underlying
3
* bean factory, shutting down the previous bean factory (if any) and
4
* initializing a fresh bean factory for the next phase of the context's lifecycle.
5
*/
6
7
protected final void refreshBeanFactory() throws BeansException {
8
if (hasBeanFactory()) {
9
// 如果存在就销毁
10
destroyBeans();
11
closeBeanFactory();
12
}
13
try {
14
// new DefaultListableBeanFactory(getInternalParentBeanFactory())
15
DefaultListableBeanFactory beanFactory = createBeanFactory();
16
// 设置序列化
17
beanFactory.setSerializationId(getId());
18
// 定制的BeanFactory
19
customizeBeanFactory(beanFactory);
20
// 使用BeanFactory加载bean定义 AbstractXmlApplicationContext
21
loadBeanDefinitions(beanFactory);
22
synchronized (this.beanFactoryMonitor) {
23
this.beanFactory = beanFactory;
24
}
25
}
26
catch (IOException ex) {
27
throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
28
}
29
}
这就是刷新BeanFactory的过程，首先判断是否存在了 BeanFactory，如果存在BeanFactory则销毁，调用 createBeanFactory 方法创建BeanFactory，但是该方法创建的是DefaultListableBeanFactory ，那么也就是说，DefaultListableBeanFactory 就是 BeanFactory的默认实现。
在AbstractRefreshableApplicationContext的refreshBeanFactory()方法中可以看见一句代码：loadBeanDefinitions(beanFactory)，该方法的作用是加载 Definitions，Definition 是spring的核心之一，代表着 IOC 中的基本数据结构。该loadBeanDefinitions(beanFactory)方法也是个抽象方法，默认实现是 AbstractXmlApplicationContext的loadBeanDefinitions(beanFactory)，其代码如下：
/**
* Loads the bean definitions via an XmlBeanDefinitionReader.
* @see org.springframework.beans.factory.xml.XmlBeanDefinitionReader
* @see #initBeanDefinitionReader
* @see #loadBeanDefinitions
*/
@Override
protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
// Create a new XmlBeanDefinitionReader for the given BeanFactory.
XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);
// Configure the bean definition reader with this context's
// resource loading environment.
beanDefinitionReader.setEnvironment(this.getEnvironment());
beanDefinitionReader.setResourceLoader(this);
beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));
// Allow a subclass to provide custom initialization of the reader,
// then proceed with actually loading the bean definitions.
initBeanDefinitionReader(beanDefinitionReader);
loadBeanDefinitions(beanDefinitionReader);
}
22
1
/**
2
* Loads the bean definitions via an XmlBeanDefinitionReader.
3
* @see org.springframework.beans.factory.xml.XmlBeanDefinitionReader
4
* @see #initBeanDefinitionReader
5
* @see #loadBeanDefinitions
6
*/
7
8
protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
9
// Create a new XmlBeanDefinitionReader for the given BeanFactory.
10
XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);
11
12
// Configure the bean definition reader with this context's
13
// resource loading environment.
14
beanDefinitionReader.setEnvironment(this.getEnvironment());
15
beanDefinitionReader.setResourceLoader(this);
16
beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));
17
18
// Allow a subclass to provide custom initialization of the reader,
19
// then proceed with actually loading the bean definitions.
20
initBeanDefinitionReader(beanDefinitionReader);
21
loadBeanDefinitions(beanDefinitionReader);
22
}
该方法首先创建一个 XmlBeanDefinitionReader ，用于读取XML中配置，设置了环境、资源加载器，最后初始化，加载。该方法主要是加载
BeanDefinition，解析Bean的定义，也就是把xml中定义数据结构转化为 IOC容器中的特定数据结构。
而比较关键的代码则是最后一行的 loadBeanDefinitions(beanDefinitionReader) 方法。
loadBeanDefinitions(beanDefinitionReader) 方法：
/**
* Load the bean definitions with the given XmlBeanDefinitionReader.
* <p>The lifecycle of the bean factory is handled by the {@link #refreshBeanFactory}
* method; hence this method is just supposed to load and/or register bean definitions.
* @param reader the XmlBeanDefinitionReader to use
* @throws BeansException in case of bean registration errors
* @throws IOException if the required XML document isn't found
* @see #refreshBeanFactory
* @see #getConfigLocations
* @see #getResources
* @see #getResourcePatternResolver
*/
protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException {
Resource[] configResources = getConfigResources();
if (configResources != null) {
reader.loadBeanDefinitions(configResources);
}
String[] configLocations = getConfigLocations();
if (configLocations != null) {
// 加载给定的路径文件
reader.loadBeanDefinitions(configLocations);
}
}
23
1
/**
2
* Load the bean definitions with the given XmlBeanDefinitionReader.
3
* <p>The lifecycle of the bean factory is handled by the {@link #refreshBeanFactory}
4
* method; hence this method is just supposed to load and/or register bean definitions.
5
* @param reader the XmlBeanDefinitionReader to use
6
* @throws BeansException in case of bean registration errors
7
* @throws IOException if the required XML document isn't found
8
* @see #refreshBeanFactory
9
* @see #getConfigLocations
10
* @see #getResources
11
* @see #getResourcePatternResolver
12
*/
13
protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException {
14
Resource[] configResources = getConfigResources();
15
if (configResources != null) {
16
reader.loadBeanDefinitions(configResources);
17
}
18
String[] configLocations = getConfigLocations();
19
if (configLocations != null) {
20
// 加载给定的路径文件
21
reader.loadBeanDefinitions(configLocations);
22
}
23
}
dubug进去看到如图：
configResources 为 null， 表示不会进入第一个语句块，会进入第二个语句块。
loadBeanDefinitions(String... locations) 方法：
@Override
public int loadBeanDefinitions(String... locations) throws BeanDefinitionStoreException {
Assert.notNull(locations, "Location array must not be null");
int counter = 0;
for (String location : locations) {
counter += loadBeanDefinitions(location);
}
return counter;
}
9
1
2
public int loadBeanDefinitions(String... locations) throws BeanDefinitionStoreException {
3
Assert.notNull(locations, "Location array must not be null");
4
int counter = 0;
5
for (String location : locations) {
6
counter += loadBeanDefinitions(location);
7
}
8
return counter;
9
}
该方法的接口介绍：
/**
* 从指定的资源位置加载bean定义。
* Load bean definitions from the specified resource locations.
* @param locations the resource locations, to be loaded with the ResourceLoader
* (or ResourcePatternResolver) of this bean definition reader
* @return the number of bean definitions found
* @throws BeanDefinitionStoreException in case of loading or parsing errors
*/
int loadBeanDefinitions(String... locations) throws BeanDefinitionStoreException;
9
1
/**
2
* 从指定的资源位置加载bean定义。
3
* Load bean definitions from the specified resource locations.
4
* @param locations the resource locations, to be loaded with the ResourceLoader
5
* (or ResourcePatternResolver) of this bean definition reader
6
* @return the number of bean definitions found
7
* @throws BeanDefinitionStoreException in case of loading or parsing errors
8
*/
9
int loadBeanDefinitions(String... locations) throws BeanDefinitionStoreException;
该
loadBeanDefinitions(String... locations) 方法的核心逻辑是for循环中的 loadBeanDefinitions(location); 该代码最后调用AbstractBeanDefinitionReader.loadBeanDefinitions(String location, @Nullable Set<Resource> actualResources)方法。
loadBeanDefinitions(String location, @Nullable Set<Resource> actualResources) 方法 ：
/**
* Load bean definitions from the specified resource location.
* <p>The location can also be a location pattern, provided that the
* ResourceLoader of this bean definition reader is a ResourcePatternResolver.
* @param location the resource location, to be loaded with the ResourceLoader
* (or ResourcePatternResolver) of this bean definition reader
* @param actualResources a Set to be filled with the actual Resource objects
* that have been resolved during the loading process. May be {@code null}
* to indicate that the caller is not interested in those Resource objects.
* @return the number of bean definitions found
* @throws BeanDefinitionStoreException in case of loading or parsing errors
* @see #getResourceLoader()
* @see #loadBeanDefinitions(org.springframework.core.io.Resource)
* @see #loadBeanDefinitions(org.springframework.core.io.Resource[])
*/
public int loadBeanDefinitions(String location, @Nullable Set<Resource> actualResources) throws BeanDefinitionStoreException {
// 获取资源加载器
ResourceLoader resourceLoader = getResourceLoader();
if (resourceLoader == null) {
throw new BeanDefinitionStoreException(
"Cannot import bean definitions from location [" + location + "]: no ResourceLoader available");
}
if (resourceLoader instanceof ResourcePatternResolver) {
// Resource pattern matching available.
try {
// 获取资源数组
Resource[] resources = ((ResourcePatternResolver) resourceLoader).getResources(location);
// 根据配置文件加载bean definitions
int loadCount = loadBeanDefinitions(resources);
if (actualResources != null) {
for (Resource resource : resources) {
actualResources.add(resource);
}
}
if (logger.isDebugEnabled()) {
logger.debug("Loaded " + loadCount + " bean definitions from location pattern [" + location + "]");
}
return loadCount;
}
catch (IOException ex) {
throw new BeanDefinitionStoreException(
"Could not resolve bean definition resource pattern [" + location + "]", ex);
}
}
else {
// Can only load single resources by absolute URL.
Resource resource = resourceLoader.getResource(location);
int loadCount = loadBeanDefinitions(resource);
if (actualResources != null) {
actualResources.add(resource);
}
if (logger.isDebugEnabled()) {
logger.debug("Loaded " + loadCount + " bean definitions from location [" + location + "]");
}
return loadCount;
}
}
58
1
/**
2
* Load bean definitions from the specified resource location.
3
* <p>The location can also be a location pattern, provided that the
4
* ResourceLoader of this bean definition reader is a ResourcePatternResolver.
5
* @param location the resource location, to be loaded with the ResourceLoader
6
* (or ResourcePatternResolver) of this bean definition reader
7
* @param actualResources a Set to be filled with the actual Resource objects
8
* that have been resolved during the loading process. May be {@code null}
9
* to indicate that the caller is not interested in those Resource objects.
10
* @return the number of bean definitions found
11
* @throws BeanDefinitionStoreException in case of loading or parsing errors
12
* @see #getResourceLoader()
13
* @see #loadBeanDefinitions(org.springframework.core.io.Resource)
14
* @see #loadBeanDefinitions(org.springframework.core.io.Resource[])
15
*/
16
public int loadBeanDefinitions(String location, Set<Resource> actualResources) throws BeanDefinitionStoreException {
17
// 获取资源加载器
18
ResourceLoader resourceLoader = getResourceLoader();
19
if (resourceLoader == null) {
20
throw new BeanDefinitionStoreException(
21
"Cannot import bean definitions from location [" + location + "]: no ResourceLoader available");
22
}
23
24
if (resourceLoader instanceof ResourcePatternResolver) {
25
// Resource pattern matching available.
26
try {
27
// 获取资源数组
28
Resource[] resources = ((ResourcePatternResolver) resourceLoader).getResources(location);
29
// 根据配置文件加载bean definitions
30
int loadCount = loadBeanDefinitions(resources);
31
if (actualResources != null) {
32
for (Resource resource : resources) {
33
actualResources.add(resource);
34
}
35
}
36
if (logger.isDebugEnabled()) {
37
logger.debug("Loaded " + loadCount + " bean definitions from location pattern [" + location + "]");
38
}
39
return loadCount;
40
}
41
catch (IOException ex) {
42
throw new BeanDefinitionStoreException(
43
"Could not resolve bean definition resource pattern [" + location + "]", ex);
44
}
45
}
46
else {
47
// Can only load single resources by absolute URL.
48
Resource resource = resourceLoader.getResource(location);
49
int loadCount = loadBeanDefinitions(resource);
50
if (actualResources != null) {
51
actualResources.add(resource);
52
}
53
if (logger.isDebugEnabled()) {
54
logger.debug("Loaded " + loadCount + " bean definitions from location [" + location + "]");
55
}
56
return loadCount;
57
}
58
}
如上图：该方法首先获取资源加载器，然后进入 if 块，获取资源数组，调用 loadBeanDefinitions(resources) ，根据配置文件加载Bean定义。
主要看看 loadBeanDefinitions(resources) 的实现，
loadBeanDefinitions(Resource... resources) 方法 ：
@Override
public int loadBeanDefinitions(Resource... resources) throws BeanDefinitionStoreException {
Assert.notNull(resources, "Resource array must not be null");
int counter = 0;
for (Resource resource : resources) {
counter += loadBeanDefinitions(resource);
}
return counter;
}
9
1
2
public int loadBeanDefinitions(Resource... resources) throws BeanDefinitionStoreException {
3
Assert.notNull(resources, "Resource array must not be null");
4
int counter = 0;
5
for (Resource resource : resources) {
6
counter += loadBeanDefinitions(resource);
7
}
8
return counter;
9
}
该方法主要在循环加载resource 资源数组，看看其加载resource 资源数组的实现 -- int loadBeanDefinitions(Resource resource) 接口， 进入该接口的 XmlBeanDefinitionReader 实现，该实现方法会调用loadBeanDefinitions(EncodedResource encodedResource)方法。
该loadBeanDefinitions(EncodedResource encodedResource)方法主要调用doLoadBeanDefinitions(inputSource, encodedResource.getResource());方法
doLoadBeanDefinitions(InputSource inputSource, Resource resource)方法：
/**
* Actually load bean definitions from the specified XML file.
* @param inputSource the SAX InputSource to read from
* @param resource the resource descriptor for the XML file
* @return the number of bean definitions found
* @throws BeanDefinitionStoreException in case of loading or parsing errors
* @see #doLoadDocument
* @see #registerBeanDefinitions
*/
protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)
throws BeanDefinitionStoreException {
try {
Document doc = doLoadDocument(inputSource, resource);
return registerBeanDefinitions(doc, resource);
}
catch (BeanDefinitionStoreException ex) {
throw ex;
}
catch (SAXParseException ex) {
throw new XmlBeanDefinitionStoreException(resource.getDescription(),
"Line " + ex.getLineNumber() + " in XML document from " + resource + " is invalid", ex);
}
catch (SAXException ex) {
throw new XmlBeanDefinitionStoreException(resource.getDescription(),
"XML document from " + resource + " is invalid", ex);
}
catch (ParserConfigurationException ex) {
throw new BeanDefinitionStoreException(resource.getDescription(),
"Parser configuration exception parsing XML from " + resource, ex);
}
catch (IOException ex) {
throw new BeanDefinitionStoreException(resource.getDescription(),
"IOException parsing XML document from " + resource, ex);
}
catch (Throwable ex) {
throw new BeanDefinitionStoreException(resource.getDescription(),
"Unexpected exception parsing XML document from " + resource, ex);
}
}
39
1
/**
2
* Actually load bean definitions from the specified XML file.
3
* @param inputSource the SAX InputSource to read from
4
* @param resource the resource descriptor for the XML file
5
* @return the number of bean definitions found
6
* @throws BeanDefinitionStoreException in case of loading or parsing errors
7
* @see #doLoadDocument
8
* @see #registerBeanDefinitions
9
*/
10
protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)
11
throws BeanDefinitionStoreException {
12
try {
13
Document doc = doLoadDocument(inputSource, resource);
14
return registerBeanDefinitions(doc, resource);
15
}
16
catch (BeanDefinitionStoreException ex) {
17
throw ex;
18
}
19
catch (SAXParseException ex) {
20
throw new XmlBeanDefinitionStoreException(resource.getDescription(),
21
"Line " + ex.getLineNumber() + " in XML document from " + resource + " is invalid", ex);
22
}
23
catch (SAXException ex) {
24
throw new XmlBeanDefinitionStoreException(resource.getDescription(),
25
"XML document from " + resource + " is invalid", ex);
26
}
27
catch (ParserConfigurationException ex) {
28
throw new BeanDefinitionStoreException(resource.getDescription(),
29
"Parser configuration exception parsing XML from " + resource, ex);
30
}
31
catch (IOException ex) {
32
throw new BeanDefinitionStoreException(resource.getDescription(),
33
"IOException parsing XML document from " + resource, ex);
34
}
35
catch (Throwable ex) {
36
throw new BeanDefinitionStoreException(resource.getDescription(),
37
"Unexpected exception parsing XML document from " + resource, ex);
38
}
39
}
该方法主要做两件事：
1、根据输入流加载 Document 文档对象
2、根据得到的文档对象注册到容器
看看
根据得到的文档对象注册到容器 的实现：
registerBeanDefinitions(Document doc, Resource resource)方法：
/**
* Register the bean definitions contained in the given DOM document.
* Called by {@code loadBeanDefinitions}.
* <p>Creates a new instance of the parser class and invokes
* {@code registerBeanDefinitions} on it.
* @param doc the DOM document
* @param resource the resource descriptor (for context information)
* @return the number of bean definitions found
* @throws BeanDefinitionStoreException in case of parsing errors
* @see #loadBeanDefinitions
* @see #setDocumentReaderClass
* @see BeanDefinitionDocumentReader#registerBeanDefinitions
*/
public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {
// 创建一个 BeanDefinitionDocumentReader， 用于读取 BeanDefinition
BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();
int countBefore = getRegistry().getBeanDefinitionCount();
documentReader.registerBeanDefinitions(doc, createReaderContext(resource));
return getRegistry().getBeanDefinitionCount() - countBefore;
}
20
1
/**
2
* Register the bean definitions contained in the given DOM document.
3
* Called by {@code loadBeanDefinitions}.
4
* <p>Creates a new instance of the parser class and invokes
5
* {@code registerBeanDefinitions} on it.
6
* @param doc the DOM document
7
* @param resource the resource descriptor (for context information)
8
* @return the number of bean definitions found
9
* @throws BeanDefinitionStoreException in case of parsing errors
10
* @see #loadBeanDefinitions
11
* @see #setDocumentReaderClass
12
* @see BeanDefinitionDocumentReader#registerBeanDefinitions
13
*/
14
public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {
15
// 创建一个 BeanDefinitionDocumentReader， 用于读取 BeanDefinition
16
BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();
17
int countBefore = getRegistry().getBeanDefinitionCount();
18
documentReader.registerBeanDefinitions(doc, createReaderContext(resource));
19
return getRegistry().getBeanDefinitionCount() - countBefore;
20
}
其中documentReader调用registerBeanDefinitions(doc, createReaderContext(resource));，
registerBeanDefinitions(Document doc, XmlReaderContext readerContext) 方法：
/**
* This implementation parses bean definitions according to the "spring-beans" XSD
* (or DTD, historically).
* <p>Opens a DOM Document; then initializes the default settings
* specified at the {@code <beans/>} level; then parses the contained bean definitions.
*/
@Override
public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {
this.readerContext = readerContext;
logger.debug("Loading bean definitions");
Element root = doc.getDocumentElement();
doRegisterBeanDefinitions(root);
}
13
1
/**
2
* This implementation parses bean definitions according to the "spring-beans" XSD
3
* (or DTD, historically).
4
* <p>Opens a DOM Document; then initializes the default settings
5
* specified at the {@code <beans/>} level; then parses the contained bean definitions.
6
*/
7
8
public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {
9
this.readerContext = readerContext;
10
logger.debug("Loading bean definitions");
11
Element root = doc.getDocumentElement();
12
doRegisterBeanDefinitions(root);
13
}
该方法从文档对象Document中获取根元素，最后调用 DefaultBeanDefinitionDocumentReader.doRegisterBeanDefinitions(root) 进行注册。
该doRegisterBeanDefinitions(Element root)方法：
/**
* Register each bean definition within the given root {@code <beans/>} element.
*/
protected void doRegisterBeanDefinitions(Element root) {
// Any nested <beans> elements will cause recursion in this method. In
// order to propagate and preserve <beans> default-* attributes correctly,
// keep track of the current (parent) delegate, which may be null. Create
// the new (child) delegate with a reference to the parent for fallback purposes,
// then ultimately reset this.delegate back to its original (parent) reference.
// this behavior emulates a stack of delegates without actually necessitating one.
BeanDefinitionParserDelegate parent = this.delegate;
this.delegate = createDelegate(getReaderContext(), root, parent);
if (this.delegate.isDefaultNamespace(root)) {
String profileSpec = root.getAttribute(PROFILE_ATTRIBUTE);
if (StringUtils.hasText(profileSpec)) {
String[] specifiedProfiles = StringUtils.tokenizeToStringArray(
profileSpec, BeanDefinitionParserDelegate.MULTI_VALUE_ATTRIBUTE_DELIMITERS);
if (!getReaderContext().getEnvironment().acceptsProfiles(specifiedProfiles)) {
if (logger.isInfoEnabled()) {
logger.info("Skipped XML bean definition file due to specified profiles [" + profileSpec +
"] not matching: " + getReaderContext().getResource());
}
return;
}
}
}
preProcessXml(root);
parseBeanDefinitions(root, this.delegate);
postProcessXml(root);
this.delegate = parent;
}
33
1
/**
2
* Register each bean definition within the given root {@code <beans/>} element.
3
*/
4
protected void doRegisterBeanDefinitions(Element root) {
5
// Any nested <beans> elements will cause recursion in this method. In
6
// order to propagate and preserve <beans> default-* attributes correctly,
7
// keep track of the current (parent) delegate, which may be null. Create
8
// the new (child) delegate with a reference to the parent for fallback purposes,
9
// then ultimately reset this.delegate back to its original (parent) reference.
10
// this behavior emulates a stack of delegates without actually necessitating one.
11
BeanDefinitionParserDelegate parent = this.delegate;
12
this.delegate = createDelegate(getReaderContext(), root, parent);
13
14
if (this.delegate.isDefaultNamespace(root)) {
15
String profileSpec = root.getAttribute(PROFILE_ATTRIBUTE);
16
if (StringUtils.hasText(profileSpec)) {
17
String[] specifiedProfiles = StringUtils.tokenizeToStringArray(
18
profileSpec, BeanDefinitionParserDelegate.MULTI_VALUE_ATTRIBUTE_DELIMITERS);
19
if (!getReaderContext().getEnvironment().acceptsProfiles(specifiedProfiles)) {
20
if (logger.isInfoEnabled()) {
21
logger.info("Skipped XML bean definition file due to specified profiles [" + profileSpec +
22
"] not matching: " + getReaderContext().getResource());
23
}
24
return;
25
}
26
}
27
}
28
29
preProcessXml(root);
30
parseBeanDefinitions(root, this.delegate);
31
postProcessXml(root);
32
this.delegate = parent;
33
}
该方法最重要的是倒数第三行的：parseBeanDefinitions(root, this.delegate);
parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate)方法：
/**
* Parse the elements at the root level in the document:
* "import", "alias", "bean".
* @param root the DOM root element of the document
*/
protected void parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate) {
if (delegate.isDefaultNamespace(root)) {
NodeList nl = root.getChildNodes();
for (int i = 0; i < nl.getLength(); i++) {
Node node = nl.item(i);
if (node instanceof Element) {
Element ele = (Element) node;
if (delegate.isDefaultNamespace(ele)) {
parseDefaultElement(ele, delegate);
}
else {
delegate.parseCustomElement(ele);
}
}
}
}
else {
delegate.parseCustomElement(root);
}
}
25
1
/**
2
* Parse the elements at the root level in the document:
3
* "import", "alias", "bean".
4
* @param root the DOM root element of the document
5
*/
6
protected void parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate) {
7
if (delegate.isDefaultNamespace(root)) {
8
NodeList nl = root.getChildNodes();
9
for (int i = 0; i < nl.getLength(); i++) {
10
Node node = nl.item(i);
11
if (node instanceof Element) {
12
Element ele = (Element) node;
13
if (delegate.isDefaultNamespace(ele)) {
14
parseDefaultElement(ele, delegate);
15
}
16
else {
17
delegate.parseCustomElement(ele);
18
}
19
}
20
}
21
}
22
else {
23
delegate.parseCustomElement(root);
24
}
25
}
该方法就是一个解析XML 文档的步骤，核心是调用 parseDefaultElement(ele, delegate)
而 parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) 方法主要是调用processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate)方法
processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate)方法:
/**
* Process the given bean element, parsing the bean definition
* and registering it with the registry.
*/
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
// 创建一个 BeanDefinitionHolder
BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
if (bdHolder != null) {
bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
try {
// Register the final decorated instance.
// 执行容器通知事件
BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry());
}
catch (BeanDefinitionStoreException ex) {
getReaderContext().error("Failed to register bean definition with name '" +
bdHolder.getBeanName() + "'", ele, ex);
}
// Send registration event.
getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder));
}
}
22
1
/**
2
* Process the given bean element, parsing the bean definition
3
* and registering it with the registry.
4
*/
5
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
6
// 创建一个 BeanDefinitionHolder
7
BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
8
if (bdHolder != null) {
9
bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
10
try {
11
// Register the final decorated instance.
12
// 执行容器通知事件
13
BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry());
14
}
15
catch (BeanDefinitionStoreException ex) {
16
getReaderContext().error("Failed to register bean definition with name '" +
17
bdHolder.getBeanName() + "'", ele, ex);
18
}
19
// Send registration event.
20
getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder));
21
}
22
}
其中，该静态方法registerBeanDefinition(BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)：
/**
* Register the given bean definition with the given bean factory.
* @param definitionHolder the bean definition including name and aliases
* @param registry the bean factory to register with
* @throws BeanDefinitionStoreException if registration failed
*/
public static void registerBeanDefinition(
BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
throws BeanDefinitionStoreException {
// Register bean definition under primary name.
// 从bean的持有者那里获取了beanName
String beanName = definitionHolder.getBeanName();
// 将bena的名字和 BeanDefinition 注册
registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());
// Register aliases for bean name, if any.
String[] aliases = definitionHolder.getAliases();
if (aliases != null) {
for (String alias : aliases) {
registry.registerAlias(beanName, alias);
}
}
}
24
1
/**
2
* Register the given bean definition with the given bean factory.
3
* @param definitionHolder the bean definition including name and aliases
4
* @param registry the bean factory to register with
5
* @throws BeanDefinitionStoreException if registration failed
6
*/
7
public static void registerBeanDefinition(
8
BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
9
throws BeanDefinitionStoreException {
10
11
// Register bean definition under primary name.
12
// 从bean的持有者那里获取了beanName
13
String beanName = definitionHolder.getBeanName();
14
// 将bena的名字和 BeanDefinition 注册
15
registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());
16
17
// Register aliases for bean name, if any.
18
String[] aliases = definitionHolder.getAliases();
19
if (aliases != null) {
20
for (String alias : aliases) {
21
registry.registerAlias(beanName, alias);
22
}
23
}
24
}
其注册接口registerBeanDefinition(String beanName, BeanDefinition beanDefinition)的DefaultListableBeanFactory类的实现：
@Override
public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
throws BeanDefinitionStoreException {
Assert.hasText(beanName, "Bean name must not be empty");
Assert.notNull(beanDefinition, "BeanDefinition must not be null");
if (beanDefinition instanceof AbstractBeanDefinition) {
try {
((AbstractBeanDefinition) beanDefinition).validate();
}
catch (BeanDefinitionValidationException ex) {
throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
"Validation of bean definition failed", ex);
}
}
BeanDefinition existingDefinition = this.beanDefinitionMap.get(beanName);
if (existingDefinition != null) {
if (!isAllowBeanDefinitionOverriding()) {
throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
"Cannot register bean definition [" + beanDefinition + "] for bean '" + beanName +
"': There is already [" + existingDefinition + "] bound.");
}
else if (existingDefinition.getRole() < beanDefinition.getRole()) {
// e.g. was ROLE_APPLICATION, now overriding with ROLE_SUPPORT or ROLE_INFRASTRUCTURE
if (logger.isWarnEnabled()) {
logger.warn("Overriding user-defined bean definition for bean '" + beanName +
"' with a framework-generated bean definition: replacing [" +
existingDefinition + "] with [" + beanDefinition + "]");
}
}
else if (!beanDefinition.equals(existingDefinition)) {
if (logger.isInfoEnabled()) {
logger.info("Overriding bean definition for bean '" + beanName +
"' with a different definition: replacing [" + existingDefinition +
"] with [" + beanDefinition + "]");
}
}
else {
if (logger.isDebugEnabled()) {
logger.debug("Overriding bean definition for bean '" + beanName +
"' with an equivalent definition: replacing [" + existingDefinition +
"] with [" + beanDefinition + "]");
}
}
this.beanDefinitionMap.put(beanName, beanDefinition);
}
else {
if (hasBeanCreationStarted()) {
// Cannot modify startup-time collection elements anymore (for stable iteration)
synchronized (this.beanDefinitionMap) {
this.beanDefinitionMap.put(beanName, beanDefinition);
List<String> updatedDefinitions = new ArrayList<>(this.beanDefinitionNames.size() + 1);
updatedDefinitions.addAll(this.beanDefinitionNames);
updatedDefinitions.add(beanName);
this.beanDefinitionNames = updatedDefinitions;
if (this.manualSingletonNames.contains(beanName)) {
Set<String> updatedSingletons = new LinkedHashSet<>(this.manualSingletonNames);
updatedSingletons.remove(beanName);
this.manualSingletonNames = updatedSingletons;
}
}
}
else {
// Still in startup registration phase -- 最终放进这个map 实现注册
this.beanDefinitionMap.put(beanName, beanDefinition);// 走这里 // private final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<>(256);
this.beanDefinitionNames.add(beanName);
this.manualSingletonNames.remove(beanName);
}
this.frozenBeanDefinitionNames = null;
}
if (existingDefinition != null || containsSingleton(beanName)) {
resetBeanDefinition(beanName);
}
}
77
1
2
public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
3
throws BeanDefinitionStoreException {
4
5
Assert.hasText(beanName, "Bean name must not be empty");
6
Assert.notNull(beanDefinition, "BeanDefinition must not be null");
7
8
if (beanDefinition instanceof AbstractBeanDefinition) {
9
try {
10
((AbstractBeanDefinition) beanDefinition).validate();
11
}
12
catch (BeanDefinitionValidationException ex) {
13
throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
14
"Validation of bean definition failed", ex);
15
}
16
}
17
18
BeanDefinition existingDefinition = this.beanDefinitionMap.get(beanName);
19
if (existingDefinition != null) {
20
if (!isAllowBeanDefinitionOverriding()) {
21
throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
22
"Cannot register bean definition [" + beanDefinition + "] for bean '" + beanName +
23
"': There is already [" + existingDefinition + "] bound.");
24
}
25
else if (existingDefinition.getRole() < beanDefinition.getRole()) {
26
// e.g. was ROLE_APPLICATION, now overriding with ROLE_SUPPORT or ROLE_INFRASTRUCTURE
27
if (logger.isWarnEnabled()) {
28
logger.warn("Overriding user-defined bean definition for bean '" + beanName +
29
"' with a framework-generated bean definition: replacing [" +
30
existingDefinition + "] with [" + beanDefinition + "]");
31
}
32
}
33
else if (!beanDefinition.equals(existingDefinition)) {
34
if (logger.isInfoEnabled()) {
35
logger.info("Overriding bean definition for bean '" + beanName +
36
"' with a different definition: replacing [" + existingDefinition +
37
"] with [" + beanDefinition + "]");
38
}
39
}
40
else {
41
if (logger.isDebugEnabled()) {
42
logger.debug("Overriding bean definition for bean '" + beanName +
43
"' with an equivalent definition: replacing [" + existingDefinition +
44
"] with [" + beanDefinition + "]");
45
}
46
}
47
this.beanDefinitionMap.put(beanName, beanDefinition);
48
}
49
else {
50
if (hasBeanCreationStarted()) {
51
// Cannot modify startup-time collection elements anymore (for stable iteration)
52
synchronized (this.beanDefinitionMap) {
53
this.beanDefinitionMap.put(beanName, beanDefinition);
54
List<String> updatedDefinitions = new ArrayList<>(this.beanDefinitionNames.size() + 1);
55
updatedDefinitions.addAll(this.beanDefinitionNames);
56
updatedDefinitions.add(beanName);
57
this.beanDefinitionNames = updatedDefinitions;
58
if (this.manualSingletonNames.contains(beanName)) {
59
Set<String> updatedSingletons = new LinkedHashSet<>(this.manualSingletonNames);
60
updatedSingletons.remove(beanName);
61
this.manualSingletonNames = updatedSingletons;
62
}
63
}
64
}
65
else {
66
// Still in startup registration phase -- 最终放进这个map 实现注册
67
this.beanDefinitionMap.put(beanName, beanDefinition);// 走这里 // private final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<>(256);
68
this.beanDefinitionNames.add(beanName);
69
this.manualSingletonNames.remove(beanName);
70
}
71
this.frozenBeanDefinitionNames = null;
72
}
73
74
if (existingDefinition != null || containsSingleton(beanName)) {
75
resetBeanDefinition(beanName);
76
}
77
}
该方法可以说是注册bean的最后一步，将beanName和 beanDefinition 放进一个 ConcurrentHashMap（256） 中。
前面忽略了
beanDefinition 的创建，beanDefinition 是在DefaultBeanDefinitionDocumentReader.processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) 方法中，在这里创建了 BeanDefinitionHolder， 而创建了 BeanDefinitionHolder实例中解析Bean并将Bean 保存在该对象中。
该实例会调用 parseBeanDefinitionElement(Element ele, @Nullable BeanDefinition containingBean) 方法，该方法用于解析XML文件并创建一个 BeanDefinitionHolder 返回，该方法会调用 parseBeanDefinitionElement(ele, beanName, containingBean) 方法， 我们看看该方法：
/**
* Parse the bean definition itself, without regard to name or aliases. May return
* {@code null} if problems occurred during the parsing of the bean definition.
*/
@Nullable
public AbstractBeanDefinition parseBeanDefinitionElement(
Element ele, String beanName, @Nullable BeanDefinition containingBean) {
this.parseState.push(new BeanEntry(beanName));
String className = null;
if (ele.hasAttribute(CLASS_ATTRIBUTE)) {
// 类全限定名称
className = ele.getAttribute(CLASS_ATTRIBUTE).trim();
}
String parent = null;
if (ele.hasAttribute(PARENT_ATTRIBUTE)) {
parent = ele.getAttribute(PARENT_ATTRIBUTE);
}
try {
// 创建
AbstractBeanDefinition bd = createBeanDefinition(className, parent);
parseBeanDefinitionAttributes(ele, beanName, containingBean, bd);
bd.setDescription(DomUtils.getChildElementValueByTagName(ele, DESCRIPTION_ELEMENT));
parseMetaElements(ele, bd);
parseLookupOverrideSubElements(ele, bd.getMethodOverrides());
parseReplacedMethodSubElements(ele, bd.getMethodOverrides());
parseConstructorArgElements(ele, bd);
parsePropertyElements(ele, bd);
parseQualifierElements(ele, bd);
bd.setResource(this.readerContext.getResource());
bd.setSource(extractSource(ele));
return bd;
}
catch (ClassNotFoundException ex) {
error("Bean class [" + className + "] not found", ele, ex);
}
catch (NoClassDefFoundError err) {
error("Class that bean class [" + className + "] depends on not found", ele, err);
}
catch (Throwable ex) {
error("Unexpected failure during bean definition parsing", ele, ex);
}
finally {
this.parseState.pop();
}
return null;
}
55
1
/**
2
* Parse the bean definition itself, without regard to name or aliases. May return
3
* {@code null} if problems occurred during the parsing of the bean definition.
4
*/
5
6
public AbstractBeanDefinition parseBeanDefinitionElement(
7
Element ele, String beanName, BeanDefinition containingBean) {
8
9
this.parseState.push(new BeanEntry(beanName));
10
11
String className = null;
12
if (ele.hasAttribute(CLASS_ATTRIBUTE)) {
13
// 类全限定名称
14
className = ele.getAttribute(CLASS_ATTRIBUTE).trim();
15
}
16
String parent = null;
17
if (ele.hasAttribute(PARENT_ATTRIBUTE)) {
18
parent = ele.getAttribute(PARENT_ATTRIBUTE);
19
}
20
21
try {
22
// 创建
23
AbstractBeanDefinition bd = createBeanDefinition(className, parent);
24
25
parseBeanDefinitionAttributes(ele, beanName, containingBean, bd);
26
bd.setDescription(DomUtils.getChildElementValueByTagName(ele, DESCRIPTION_ELEMENT));
27
28
parseMetaElements(ele, bd);
29
parseLookupOverrideSubElements(ele, bd.getMethodOverrides());
30
parseReplacedMethodSubElements(ele, bd.getMethodOverrides());
31
32
parseConstructorArgElements(ele, bd);
33
parsePropertyElements(ele, bd);
34
parseQualifierElements(ele, bd);
35
36
bd.setResource(this.readerContext.getResource());
37
bd.setSource(extractSource(ele));
38
39
return bd;
40
}
41
catch (ClassNotFoundException ex) {
42
error("Bean class [" + className + "] not found", ele, ex);
43
}
44
catch (NoClassDefFoundError err) {
45
error("Class that bean class [" + className + "] depends on not found", ele, err);
46
}
47
catch (Throwable ex) {
48
error("Unexpected failure during bean definition parsing", ele, ex);
49
}
50
finally {
51
this.parseState.pop();
52
}
53
54
return null;
55
}
该方法从XML元素中取出 class 元素，然后拿着className调用 createBeanDefinition(className, parent) 方法，该方法核心是调用 BeanDefinitionReaderUtils.createBeanDefinition 方法，我们看看该方法：
/**
* Create a new GenericBeanDefinition for the given parent name and class name,
* eagerly loading the bean class if a ClassLoader has been specified.
* @param parentName the name of the parent bean, if any
* @param className the name of the bean class, if any
* @param classLoader the ClassLoader to use for loading bean classes
* (can be {@code null} to just register bean classes by name)
* @return the bean definition
* @throws ClassNotFoundException if the bean class could not be loaded
*/
public static AbstractBeanDefinition createBeanDefinition(
@Nullable String parentName, @Nullable String className, @Nullable ClassLoader classLoader) throws ClassNotFoundException {
// 泛型的bean定义，也就是最终生成的bean定义。
GenericBeanDefinition bd = new GenericBeanDefinition();
bd.setParentName(parentName);
if (className != null) {
if (classLoader != null) {
// 设置Class 对象
bd.setBeanClass(ClassUtils.forName(className, classLoader));
}
else {
bd.setBeanClassName(className);
}
}
return bd;
}
27
1
/**
2
* Create a new GenericBeanDefinition for the given parent name and class name,
3
* eagerly loading the bean class if a ClassLoader has been specified.
4
* @param parentName the name of the parent bean, if any
5
* @param className the name of the bean class, if any
6
* @param classLoader the ClassLoader to use for loading bean classes
7
* (can be {@code null} to just register bean classes by name)
8
* @return the bean definition
9
* @throws ClassNotFoundException if the bean class could not be loaded
10
*/
11
public static AbstractBeanDefinition createBeanDefinition(
12
String parentName, String className, ClassLoader classLoader) throws ClassNotFoundException {
13
14
// 泛型的bean定义，也就是最终生成的bean定义。
15
GenericBeanDefinition bd = new GenericBeanDefinition();
16
bd.setParentName(parentName);
17
if (className != null) {
18
if (classLoader != null) {
19
// 设置Class 对象
20
bd.setBeanClass(ClassUtils.forName(className, classLoader));
21
}
22
else {
23
bd.setBeanClassName(className);
24
}
25
}
26
return bd;
27
}
该方法创建一个 Definition 的持有者，然后设置该持有者的Class对象，该对象就是我们在配置文件中配置的Class对象。最后返回。
#############创建Bean实例并构建Bean的依赖关系网###########################################
我们刚刚创建了Bean工厂，并创建 BeanDefinitions 放进Map里，以beanName为key。那么我们现在有了Bean定义，但还没有实例，也没有构建Bean与Bean之间的依赖关系。
我们知道，构建依赖关系是 IOC 的一个重要的任务，我们怎么能放过。那么是在哪里做的呢？在 refresh() 方法的finishBeanFactoryInitialization(beanFactory) 方法中。该方法中重要的一步是 ： beanFactory.preInstantiateSingletons()，我们有必要看看该方法实现：
@Override
public void preInstantiateSingletons() throws BeansException {
if (logger.isDebugEnabled()) {
logger.debug("Pre-instantiating singletons in " + this);
}
// Iterate over a copy to allow for init methods which in turn register new bean definitions.
// While this may not be part of the regular factory bootstrap, it does otherwise work fine.
List<String> beanNames = new ArrayList<>(this.beanDefinitionNames);
// Trigger initialization of all non-lazy singleton beans...
for (String beanName : beanNames) {
RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
if (isFactoryBean(beanName)) {
Object bean = getBean(FACTORY_BEAN_PREFIX + beanName);
if (bean instanceof FactoryBean) {
final FactoryBean<?> factory = (FactoryBean<?>) bean;
boolean isEagerInit;
if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
isEagerInit = AccessController.doPrivileged((PrivilegedAction<Boolean>)
((SmartFactoryBean<?>) factory)::isEagerInit,
getAccessControlContext());
}
else {
isEagerInit = (factory instanceof SmartFactoryBean &&
((SmartFactoryBean<?>) factory).isEagerInit());
}
if (isEagerInit) {
getBean(beanName);
}
}
}
else {
getBean(beanName);
}
}
}
// Trigger post-initialization callback for all applicable beans...
for (String beanName : beanNames) {
Object singletonInstance = getSingleton(beanName);
if (singletonInstance instanceof SmartInitializingSingleton) {
final SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance;
if (System.getSecurityManager() != null) {
AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
smartSingleton.afterSingletonsInstantiated();
return null;
}, getAccessControlContext());
}
else {
smartSingleton.afterSingletonsInstantiated();
}
}
}
}
56
1
2
public void preInstantiateSingletons() throws BeansException {
3
if (logger.isDebugEnabled()) {
4
logger.debug("Pre-instantiating singletons in " + this);
5
}
6
7
// Iterate over a copy to allow for init methods which in turn register new bean definitions.
8
// While this may not be part of the regular factory bootstrap, it does otherwise work fine.
9
List<String> beanNames = new ArrayList<>(this.beanDefinitionNames);
10
11
// Trigger initialization of all non-lazy singleton beans...
12
for (String beanName : beanNames) {
13
RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
14
if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
15
if (isFactoryBean(beanName)) {
16
Object bean = getBean(FACTORY_BEAN_PREFIX + beanName);
17
if (bean instanceof FactoryBean) {
18
final FactoryBean<?> factory = (FactoryBean<?>) bean;
19
boolean isEagerInit;
20
if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
21
isEagerInit = AccessController.doPrivileged((PrivilegedAction<Boolean>)
22
((SmartFactoryBean<?>) factory)::isEagerInit,
23
getAccessControlContext());
24
}
25
else {
26
isEagerInit = (factory instanceof SmartFactoryBean &&
27
((SmartFactoryBean<?>) factory).isEagerInit());
28
}
29
if (isEagerInit) {
30
getBean(beanName);
31
}
32
}
33
}
34
else {
35
getBean(beanName);
36
}
37
}
38
}
39
40
// Trigger post-initialization callback for all applicable beans...
41
for (String beanName : beanNames) {
42
Object singletonInstance = getSingleton(beanName);
43
if (singletonInstance instanceof SmartInitializingSingleton) {
44
final SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance;
45
if (System.getSecurityManager() != null) {
46
AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
47
smartSingleton.afterSingletonsInstantiated();
48
return null;
49
}, getAccessControlContext());
50
}
51
else {
52
smartSingleton.afterSingletonsInstantiated();
53
}
54
}
55
}
56
}
该方法首先循环所有的BeanNames，并且调用getBean(beanName);方法，该方法实际上就是创建bean并递归构建依赖关系。该方法会调用 doGetBean(name, null, null, false)，我们进入该方法查看，该方法很长，楼主挑选重要代码：
/**
* Return an instance, which may be shared or independent, of the specified bean.
* @param name the name of the bean to retrieve
* @param requiredType the required type of the bean to retrieve
* @param args arguments to use when creating a bean instance using explicit arguments
* (only applied when creating a new instance as opposed to retrieving an existing one)
* @param typeCheckOnly whether the instance is obtained for a type check,
* not for actual use
* @return an instance of the bean
* @throws BeansException if the bean could not be created
*/
@SuppressWarnings("unchecked")
protected <T> T doGetBean(final String name, @Nullable final Class<T> requiredType,
@Nullable final Object[] args, boolean typeCheckOnly) throws BeansException {
final String beanName = transformedBeanName(name);
Object bean;
// Eagerly check singleton cache for manually registered singletons.
Object sharedInstance = getSingleton(beanName);
if (sharedInstance != null && args == null) {
if (logger.isDebugEnabled()) {
if (isSingletonCurrentlyInCreation(beanName)) {
logger.debug("Returning eagerly cached instance of singleton bean '" + beanName +
"' that is not fully initialized yet - a consequence of a circular reference");
}
else {
logger.debug("Returning cached instance of singleton bean '" + beanName + "'");
}
}
bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
}
else {
// Fail if we're already creating this bean instance:
// We're assumably within a circular reference.
if (isPrototypeCurrentlyInCreation(beanName)) {
throw new BeanCurrentlyInCreationException(beanName);
}
// Check if bean definition exists in this factory.
BeanFactory parentBeanFactory = getParentBeanFactory();
if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
// Not found -> check parent.
String nameToLookup = originalBeanName(name);
if (parentBeanFactory instanceof AbstractBeanFactory) {
return ((AbstractBeanFactory) parentBeanFactory).doGetBean(
nameToLookup, requiredType, args, typeCheckOnly);
}
else if (args != null) {
// Delegation to parent with explicit args.
return (T) parentBeanFactory.getBean(nameToLookup, args);
}
else {
// No args -> delegate to standard getBean method.
return parentBeanFactory.getBean(nameToLookup, requiredType);
}
}
if (!typeCheckOnly) {
markBeanAsCreated(beanName);
}
try {
final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
checkMergedBeanDefinition(mbd, beanName, args);
// Guarantee initialization of beans that the current bean depends on.
String[] dependsOn = mbd.getDependsOn();
if (dependsOn != null) {
for (String dep : dependsOn) {
if (isDependent(beanName, dep)) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"Circular depends-on relationship between '" + beanName + "' and '" + dep + "'");
}
registerDependentBean(dep, beanName);
try {
getBean(dep);
}
catch (NoSuchBeanDefinitionException ex) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"'" + beanName + "' depends on missing bean '" + dep + "'", ex);
}
}
}
// Create bean instance.
if (mbd.isSingleton()) {
sharedInstance = getSingleton(beanName, () -> {
try {
return createBean(beanName, mbd, args);
}
catch (BeansException ex) {
// Explicitly remove instance from singleton cache: It might have been put there
// eagerly by the creation process, to allow for circular reference resolution.
// Also remove any beans that received a temporary reference to the bean.
destroySingleton(beanName);
throw ex;
}
});
bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
}
else if (mbd.isPrototype()) {
// It's a prototype -> create a new instance.
Object prototypeInstance = null;
try {
beforePrototypeCreation(beanName);
prototypeInstance = createBean(beanName, mbd, args);
}
finally {
afterPrototypeCreation(beanName);
}
bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
}
else {
String scopeName = mbd.getScope();
final Scope scope = this.scopes.get(scopeName);
if (scope == null) {
throw new IllegalStateException("No Scope registered for scope name '" + scopeName + "'");
}
try {
Object scopedInstance = scope.get(beanName, () -> {
beforePrototypeCreation(beanName);
try {
return createBean(beanName, mbd, args);
}
finally {
afterPrototypeCreation(beanName);
}
});
bean = getObjectForBeanInstance(scopedInstance, name, beanName, mbd);
}
catch (IllegalStateException ex) {
throw new BeanCreationException(beanName,
"Scope '" + scopeName + "' is not active for the current thread; consider " +
"defining a scoped proxy for this bean if you intend to refer to it from a singleton",
ex);
}
}
}
catch (BeansException ex) {
cleanupAfterBeanCreationFailure(beanName);
throw ex;
}
}
// Check if required type matches the type of the actual bean instance.
if (requiredType != null && !requiredType.isInstance(bean)) {
try {
T convertedBean = getTypeConverter().convertIfNecessary(bean, requiredType);
if (convertedBean == null) {
throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
}
return convertedBean;
}
catch (TypeMismatchException ex) {
if (logger.isDebugEnabled()) {
logger.debug("Failed to convert bean '" + name + "' to required type '" +
ClassUtils.getQualifiedName(requiredType) + "'", ex);
}
throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
}
}
return (T) bean;
}
167
1
/**
2
* Return an instance, which may be shared or independent, of the specified bean.
3
* @param name the name of the bean to retrieve
4
* @param requiredType the required type of the bean to retrieve
5
* @param args arguments to use when creating a bean instance using explicit arguments
6
* (only applied when creating a new instance as opposed to retrieving an existing one)
7
* @param typeCheckOnly whether the instance is obtained for a type check,
8
* not for actual use
9
* @return an instance of the bean
10
* @throws BeansException if the bean could not be created
11
*/
12
("unchecked")
13
protected <T> T doGetBean(final String name, final Class<T> requiredType,
14
final Object[] args, boolean typeCheckOnly) throws BeansException {
15
16
final String beanName = transformedBeanName(name);
17
Object bean;
18
19
// Eagerly check singleton cache for manually registered singletons.
20
Object sharedInstance = getSingleton(beanName);
21
if (sharedInstance != null && args == null) {
22
if (logger.isDebugEnabled()) {
23
if (isSingletonCurrentlyInCreation(beanName)) {
24
logger.debug("Returning eagerly cached instance of singleton bean '" + beanName +
25
"' that is not fully initialized yet - a consequence of a circular reference");
26
}
27
else {
28
logger.debug("Returning cached instance of singleton bean '" + beanName + "'");
29
}
30
}
31
bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
32
}
33
34
else {
35
// Fail if we're already creating this bean instance:
36
// We're assumably within a circular reference.
37
if (isPrototypeCurrentlyInCreation(beanName)) {
38
throw new BeanCurrentlyInCreationException(beanName);
39
}
40
41
// Check if bean definition exists in this factory.
42
BeanFactory parentBeanFactory = getParentBeanFactory();
43
if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
44
// Not found -> check parent.
45
String nameToLookup = originalBeanName(name);
46
if (parentBeanFactory instanceof AbstractBeanFactory) {
47
return ((AbstractBeanFactory) parentBeanFactory).doGetBean(
48
nameToLookup, requiredType, args, typeCheckOnly);
49
}
50
else if (args != null) {
51
// Delegation to parent with explicit args.
52
return (T) parentBeanFactory.getBean(nameToLookup, args);
53
}
54
else {
55
// No args -> delegate to standard getBean method.
56
return parentBeanFactory.getBean(nameToLookup, requiredType);
57
}
58
}
59
60
if (!typeCheckOnly) {
61
markBeanAsCreated(beanName);
62
}
63
64
try {
65
final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
66
checkMergedBeanDefinition(mbd, beanName, args);
67
68
// Guarantee initialization of beans that the current bean depends on.
69
String[] dependsOn = mbd.getDependsOn();
70
if (dependsOn != null) {
71
for (String dep : dependsOn) {
72
if (isDependent(beanName, dep)) {
73
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
74
"Circular depends-on relationship between '" + beanName + "' and '" + dep + "'");
75
}
76
registerDependentBean(dep, beanName);
77
try {
78
getBean(dep);
79
}
80
catch (NoSuchBeanDefinitionException ex) {
81
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
82
"'" + beanName + "' depends on missing bean '" + dep + "'", ex);
83
}
84
}
85
}
86
87
// Create bean instance.
88
if (mbd.isSingleton()) {
89
sharedInstance = getSingleton(beanName, () -> {
90
try {
91
return createBean(beanName, mbd, args);
92
}
93
catch (BeansException ex) {
94
// Explicitly remove instance from singleton cache: It might have been put there
95
// eagerly by the creation process, to allow for circular reference resolution.
96
// Also remove any beans that received a temporary reference to the bean.
97
destroySingleton(beanName);
98
throw ex;
99
}
100
});
101
bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
102
}
103
104
else if (mbd.isPrototype()) {
105
// It's a prototype -> create a new instance.
106
Object prototypeInstance = null;
107
try {
108
beforePrototypeCreation(beanName);
109
prototypeInstance = createBean(beanName, mbd, args);
110
}
111
finally {
112
afterPrototypeCreation(beanName);
113
}
114
bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
115
}
116
117
else {
118
String scopeName = mbd.getScope();
119
final Scope scope = this.scopes.get(scopeName);
120
if (scope == null) {
121
throw new IllegalStateException("No Scope registered for scope name '" + scopeName + "'");
122
}
123
try {
124
Object scopedInstance = scope.get(beanName, () -> {
125
beforePrototypeCreation(beanName);
126
try {
127
return createBean(beanName, mbd, args);
128
}
129
finally {
130
afterPrototypeCreation(beanName);
131
}
132
});
133
bean = getObjectForBeanInstance(scopedInstance, name, beanName, mbd);
134
}
135
catch (IllegalStateException ex) {
136
throw new BeanCreationException(beanName,
137
"Scope '" + scopeName + "' is not active for the current thread; consider " +
138
"defining a scoped proxy for this bean if you intend to refer to it from a singleton",
139
ex);
140
}
141
}
142
}
143
catch (BeansException ex) {
144
cleanupAfterBeanCreationFailure(beanName);
145
throw ex;
146
}
147
}
148
149
// Check if required type matches the type of the actual bean instance.
150
if (requiredType != null && !requiredType.isInstance(bean)) {
151
try {
152
T convertedBean = getTypeConverter().convertIfNecessary(bean, requiredType);
153
if (convertedBean == null) {
154
throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
155
}
156
return convertedBean;
157
}
158
catch (TypeMismatchException ex) {
159
if (logger.isDebugEnabled()) {
160
logger.debug("Failed to convert bean '" + name + "' to required type '" +
161
ClassUtils.getQualifiedName(requiredType) + "'", ex);
162
}
163
throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
164
}
165
}
166
return (T) bean;
167
}
其中部分重要代码截图：
可以看到，该方法首先会获取依赖关系，拿着依赖的BeanName 递归调用 getBean方法，直到调用 getSingleton 方法返回依赖bean，而 getSingleton 方法的参数是 createBean 返回的实例，该
createBean
方法内部调用 AbstractAutowireCapableBeanFactory.doCreateBean 方法：
/**
* Actually create the specified bean. Pre-creation processing has already happened
* at this point, e.g. checking {@code postProcessBeforeInstantiation} callbacks.
* <p>Differentiates between default bean instantiation, use of a
* factory method, and autowiring a constructor.
* @param beanName the name of the bean
* @param mbd the merged bean definition for the bean
* @param args explicit arguments to use for constructor or factory method invocation
* @return a new instance of the bean
* @throws BeanCreationException if the bean could not be created
* @see #instantiateBean
* @see #instantiateUsingFactoryMethod
* @see #autowireConstructor
*/
protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final @Nullable Object[] args)
throws BeanCreationException {
// Instantiate the bean.
BeanWrapper instanceWrapper = null;
if (mbd.isSingleton()) {
instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
}
if (instanceWrapper == null) {
instanceWrapper = createBeanInstance(beanName, mbd, args);
}
final Object bean = instanceWrapper.getWrappedInstance();
Class<?> beanType = instanceWrapper.getWrappedClass();
if (beanType != NullBean.class) {
mbd.resolvedTargetType = beanType;
}
// Allow post-processors to modify the merged bean definition.
synchronized (mbd.postProcessingLock) {
if (!mbd.postProcessed) {
try {
applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName);
}
catch (Throwable ex) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"Post-processing of merged bean definition failed", ex);
}
mbd.postProcessed = true;
}
}
// Eagerly cache singletons to be able to resolve circular references
// even when triggered by lifecycle interfaces like BeanFactoryAware.
boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences &&
isSingletonCurrentlyInCreation(beanName));
if (earlySingletonExposure) {
if (logger.isDebugEnabled()) {
logger.debug("Eagerly caching bean '" + beanName +
"' to allow for resolving potential circular references");
}
addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean));
}
// Initialize the bean instance.
Object exposedObject = bean;
try {
populateBean(beanName, mbd, instanceWrapper);
exposedObject = initializeBean(beanName, exposedObject, mbd);
}
catch (Throwable ex) {
if (ex instanceof BeanCreationException && beanName.equals(((BeanCreationException) ex).getBeanName())) {
throw (BeanCreationException) ex;
}
else {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Initialization of bean failed", ex);
}
}
if (earlySingletonExposure) {
Object earlySingletonReference = getSingleton(beanName, false);
if (earlySingletonReference != null) {
if (exposedObject == bean) {
exposedObject = earlySingletonReference;
}
else if (!this.allowRawInjectionDespiteWrapping && hasDependentBean(beanName)) {
String[] dependentBeans = getDependentBeans(beanName);
Set<String> actualDependentBeans = new LinkedHashSet<>(dependentBeans.length);
for (String dependentBean : dependentBeans) {
if (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) {
actualDependentBeans.add(dependentBean);
}
}
if (!actualDependentBeans.isEmpty()) {
throw new BeanCurrentlyInCreationException(beanName,
"Bean with name '" + beanName + "' has been injected into other beans [" +
StringUtils.collectionToCommaDelimitedString(actualDependentBeans) +
"] in its raw version as part of a circular reference, but has eventually been " +
"wrapped. This means that said other beans do not use the final version of the " +
"bean. This is often the result of over-eager type matching - consider using " +
"'getBeanNamesOfType' with the 'allowEagerInit' flag turned off, for example.");
}
}
}
}
// Register bean as disposable.
try {
registerDisposableBeanIfNecessary(beanName, bean, mbd);
}
catch (BeanDefinitionValidationException ex) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex);
}
return exposedObject;
}
111
1
/**
2
* Actually create the specified bean. Pre-creation processing has already happened
3
* at this point, e.g. checking {@code postProcessBeforeInstantiation} callbacks.
4
* <p>Differentiates between default bean instantiation, use of a
5
* factory method, and autowiring a constructor.
6
* @param beanName the name of the bean
7
* @param mbd the merged bean definition for the bean
8
* @param args explicit arguments to use for constructor or factory method invocation
9
* @return a new instance of the bean
10
* @throws BeanCreationException if the bean could not be created
11
* @see #instantiateBean
12
* @see #instantiateUsingFactoryMethod
13
* @see #autowireConstructor
14
*/
15
protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final Object[] args)
16
throws BeanCreationException {
17
18
// Instantiate the bean.
19
BeanWrapper instanceWrapper = null;
20
if (mbd.isSingleton()) {
21
instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
22
}
23
if (instanceWrapper == null) {
24
instanceWrapper = createBeanInstance(beanName, mbd, args);
25
}
26
final Object bean = instanceWrapper.getWrappedInstance();
27
Class<?> beanType = instanceWrapper.getWrappedClass();
28
if (beanType != NullBean.class) {
29
mbd.resolvedTargetType = beanType;
30
}
31
32
// Allow post-processors to modify the merged bean definition.
33
synchronized (mbd.postProcessingLock) {
34
if (!mbd.postProcessed) {
35
try {
36
applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName);
37
}
38
catch (Throwable ex) {
39
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
40
"Post-processing of merged bean definition failed", ex);
41
}
42
mbd.postProcessed = true;
43
}
44
}
45
46
// Eagerly cache singletons to be able to resolve circular references
47
// even when triggered by lifecycle interfaces like BeanFactoryAware.
48
boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences &&
49
isSingletonCurrentlyInCreation(beanName));
50
if (earlySingletonExposure) {
51
if (logger.isDebugEnabled()) {
52
logger.debug("Eagerly caching bean '" + beanName +
53
"' to allow for resolving potential circular references");
54
}
55
addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean));
56
}
57
58
// Initialize the bean instance.
59
Object exposedObject = bean;
60
try {
61
populateBean(beanName, mbd, instanceWrapper);
62
exposedObject = initializeBean(beanName, exposedObject, mbd);
63
}
64
catch (Throwable ex) {
65
if (ex instanceof BeanCreationException && beanName.equals(((BeanCreationException) ex).getBeanName())) {
66
throw (BeanCreationException) ex;
67
}
68
else {
69
throw new BeanCreationException(
70
mbd.getResourceDescription(), beanName, "Initialization of bean failed", ex);
71
}
72
}
73
74
if (earlySingletonExposure) {
75
Object earlySingletonReference = getSingleton(beanName, false);
76
if (earlySingletonReference != null) {
77
if (exposedObject == bean) {
78
exposedObject = earlySingletonReference;
79
}
80
else if (!this.allowRawInjectionDespiteWrapping && hasDependentBean(beanName)) {
81
String[] dependentBeans = getDependentBeans(beanName);
82
Set<String> actualDependentBeans = new LinkedHashSet<>(dependentBeans.length);
83
for (String dependentBean : dependentBeans) {
84
if (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) {
85
actualDependentBeans.add(dependentBean);
86
}
87
}
88
if (!actualDependentBeans.isEmpty()) {
89
throw new BeanCurrentlyInCreationException(beanName,
90
"Bean with name '" + beanName + "' has been injected into other beans [" +
91
StringUtils.collectionToCommaDelimitedString(actualDependentBeans) +
92
"] in its raw version as part of a circular reference, but has eventually been " +
93
"wrapped. This means that said other beans do not use the final version of the " +
94
"bean. This is often the result of over-eager type matching - consider using " +
95
"'getBeanNamesOfType' with the 'allowEagerInit' flag turned off, for example.");
96
}
97
}
98
}
99
}
100
101
// Register bean as disposable.
102
try {
103
registerDisposableBeanIfNecessary(beanName, bean, mbd);
104
}
105
catch (BeanDefinitionValidationException ex) {
106
throw new BeanCreationException(
107
mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex);
108
}
109
110
return exposedObject;
111
}
该方法很长，我们重点关注以下2行代码：
instanceWrapper = createBeanInstance(beanName, mbd, args) 创建实例。
populateBean(beanName, mbd, instanceWrapper) ， 该方法用于填充Bean，该
方法可以就是说就是发生依赖注入的地方。
createBeanInstance(beanName, mbd, args):
/**
* Create a new instance for the specified bean, using an appropriate instantiation strategy:
* factory method, constructor autowiring, or simple instantiation.
* @param beanName the name of the bean
* @param mbd the bean definition for the bean
* @param args explicit arguments to use for constructor or factory method invocation
* @return a BeanWrapper for the new instance
* @see #obtainFromSupplier
* @see #instantiateUsingFactoryMethod
* @see #autowireConstructor
* @see #instantiateBean
*/
protected BeanWrapper createBeanInstance(String beanName, RootBeanDefinition mbd, @Nullable Object[] args) {
// Make sure bean class is actually resolved at this point.
Class<?> beanClass = resolveBeanClass(mbd, beanName);
if (beanClass != null && !Modifier.isPublic(beanClass.getModifiers()) && !mbd.isNonPublicAccessAllowed()) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"Bean class isn't public, and non-public access not allowed: " + beanClass.getName());
}
Supplier<?> instanceSupplier = mbd.getInstanceSupplier();
if (instanceSupplier != null) {
return obtainFromSupplier(instanceSupplier, beanName);
}
if (mbd.getFactoryMethodName() != null) {
return instantiateUsingFactoryMethod(beanName, mbd, args);
}
// Shortcut when re-creating the same bean...
boolean resolved = false;
boolean autowireNecessary = false;
if (args == null) {
synchronized (mbd.constructorArgumentLock) {
if (mbd.resolvedConstructorOrFactoryMethod != null) {
resolved = true;
autowireNecessary = mbd.constructorArgumentsResolved;
}
}
}
if (resolved) {
if (autowireNecessary) {
return autowireConstructor(beanName, mbd, null, null);
}
else {
return instantiateBean(beanName, mbd);
}
}
// Need to determine the constructor...
Constructor<?>[] ctors = determineConstructorsFromBeanPostProcessors(beanClass, beanName);
if (ctors != null ||
mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_CONSTRUCTOR ||
mbd.hasConstructorArgumentValues() || !ObjectUtils.isEmpty(args)) {
return autowireConstructor(beanName, mbd, ctors, args);
}
// No special handling: simply use no-arg constructor.
return instantiateBean(beanName, mbd);
}
61
1
/**
2
* Create a new instance for the specified bean, using an appropriate instantiation strategy:
3
* factory method, constructor autowiring, or simple instantiation.
4
* @param beanName the name of the bean
5
* @param mbd the bean definition for the bean
6
* @param args explicit arguments to use for constructor or factory method invocation
7
* @return a BeanWrapper for the new instance
8
* @see #obtainFromSupplier
9
* @see #instantiateUsingFactoryMethod
10
* @see #autowireConstructor
11
* @see #instantiateBean
12
*/
13
protected BeanWrapper createBeanInstance(String beanName, RootBeanDefinition mbd, Object[] args) {
14
// Make sure bean class is actually resolved at this point.
15
Class<?> beanClass = resolveBeanClass(mbd, beanName);
16
17
if (beanClass != null && !Modifier.isPublic(beanClass.getModifiers()) && !mbd.isNonPublicAccessAllowed()) {
18
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
19
"Bean class isn't public, and non-public access not allowed: " + beanClass.getName());
20
}
21
22
Supplier<?> instanceSupplier = mbd.getInstanceSupplier();
23
if (instanceSupplier != null) {
24
return obtainFromSupplier(instanceSupplier, beanName);
25
}
26
27
if (mbd.getFactoryMethodName() != null) {
28
return instantiateUsingFactoryMethod(beanName, mbd, args);
29
}
30
31
// Shortcut when re-creating the same bean...
32
boolean resolved = false;
33
boolean autowireNecessary = false;
34
if (args == null) {
35
synchronized (mbd.constructorArgumentLock) {
36
if (mbd.resolvedConstructorOrFactoryMethod != null) {
37
resolved = true;
38
autowireNecessary = mbd.constructorArgumentsResolved;
39
}
40
}
41
}
42
if (resolved) {
43
if (autowireNecessary) {
44
return autowireConstructor(beanName, mbd, null, null);
45
}
46
else {
47
return instantiateBean(beanName, mbd);
48
}
49
}
50
51
// Need to determine the constructor...
52
Constructor<?>[] ctors = determineConstructorsFromBeanPostProcessors(beanClass, beanName);
53
if (ctors != null ||
54
mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_CONSTRUCTOR ||
55
mbd.hasConstructorArgumentValues() || !ObjectUtils.isEmpty(args)) {
56
return autowireConstructor(beanName, mbd, ctors, args);
57
}
58
59
// No special handling: simply use no-arg constructor.
60
return instantiateBean(beanName, mbd);
61
}
该方法的doc注释是这样介绍的：为指定的bean创建一个新的实例，使用适当的实例化策略:工厂方法、构造函数自动装配或简单实例化。
我们看，该方法首先创建Class 对象，然后获取构造器对象，最后调用 instantiateBean(beanName, mbd) 方法，
instantiateBean(beanName, mbd) 方法实现：
/**
* Instantiate the given bean using its default constructor.
* @param beanName the name of the bean
* @param mbd the bean definition for the bean
* @return a BeanWrapper for the new instance
*/
protected BeanWrapper instantiateBean(final String beanName, final RootBeanDefinition mbd) {
try {
Object beanInstance;
final BeanFactory parent = this;
if (System.getSecurityManager() != null) {
beanInstance = AccessController.doPrivileged((PrivilegedAction<Object>) () ->
getInstantiationStrategy().instantiate(mbd, beanName, parent),
getAccessControlContext());
}
else {
beanInstance = getInstantiationStrategy().instantiate(mbd, beanName, parent);
}
BeanWrapper bw = new BeanWrapperImpl(beanInstance);
initBeanWrapper(bw);
return bw;
}
catch (Throwable ex) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Instantiation of bean failed", ex);
}
}
27
1
/**
2
* Instantiate the given bean using its default constructor.
3
* @param beanName the name of the bean
4
* @param mbd the bean definition for the bean
5
* @return a BeanWrapper for the new instance
6
*/
7
protected BeanWrapper instantiateBean(final String beanName, final RootBeanDefinition mbd) {
8
try {
9
Object beanInstance;
10
final BeanFactory parent = this;
11
if (System.getSecurityManager() != null) {
12
beanInstance = AccessController.doPrivileged((PrivilegedAction<Object>) () ->
13
getInstantiationStrategy().instantiate(mbd, beanName, parent),
14
getAccessControlContext());
15
}
16
else {
17
beanInstance = getInstantiationStrategy().instantiate(mbd, beanName, parent);
18
}
19
BeanWrapper bw = new BeanWrapperImpl(beanInstance);
20
initBeanWrapper(bw);
21
return bw;
22
}
23
catch (Throwable ex) {
24
throw new BeanCreationException(
25
mbd.getResourceDescription(), beanName, "Instantiation of bean failed", ex);
26
}
27
}
该方法核心逻辑是 beanInstance = getInstantiationStrategy().instantiate(mbd, beanName, parent)，携带BeanName ,RootBeanDefinition ,发挥的策略对象是 SimpleInstantiationStrategy，该方法内部调用静态方法 BeanUtils.instantiateClass(constructorToUse)， 组后调用 Constructor 的 newInstance 方法， 也就是最终使用反射创建了该实例：
/**
* Convenience method to instantiate a class using the given constructor.
* <p>Note that this method tries to set the constructor accessible if given a
* non-accessible (that is, non-public) constructor, and supports Kotlin classes
* with optional parameters and default values.
* @param ctor the constructor to instantiate
* @param args the constructor arguments to apply (use {@code null} for an unspecified
* parameter if needed for Kotlin classes with optional parameters and default values)
* @return the new instance
* @throws BeanInstantiationException if the bean cannot be instantiated
* @see Constructor#newInstance
*/
public static <T> T instantiateClass(Constructor<T> ctor, Object... args) throws BeanInstantiationException {
Assert.notNull(ctor, "Constructor must not be null");
try {
ReflectionUtils.makeAccessible(ctor);
return (KotlinDetector.isKotlinType(ctor.getDeclaringClass()) ?
KotlinDelegate.instantiateClass(ctor, args) : ctor.newInstance(args));
}
catch (InstantiationException ex) {
throw new BeanInstantiationException(ctor, "Is it an abstract class?", ex);
}
catch (IllegalAccessException ex) {
throw new BeanInstantiationException(ctor, "Is the constructor accessible?", ex);
}
catch (IllegalArgumentException ex) {
throw new BeanInstantiationException(ctor, "Illegal arguments for constructor", ex);
}
catch (InvocationTargetException ex) {
throw new BeanInstantiationException(ctor, "Constructor threw exception", ex.getTargetException());
}
}
33
1
/**
2
* Convenience method to instantiate a class using the given constructor.
3
* <p>Note that this method tries to set the constructor accessible if given a
4
* non-accessible (that is, non-public) constructor, and supports Kotlin classes
5
* with optional parameters and default values.
6
* @param ctor the constructor to instantiate
7
* @param args the constructor arguments to apply (use {@code null} for an unspecified
8
* parameter if needed for Kotlin classes with optional parameters and default values)
9
* @return the new instance
10
* @throws BeanInstantiationException if the bean cannot be instantiated
11
* @see Constructor#newInstance
12
*/
13
public static <T> T instantiateClass(Constructor<T> ctor, Object... args) throws BeanInstantiationException {
14
Assert.notNull(ctor, "Constructor must not be null");
15
try {
16
ReflectionUtils.makeAccessible(ctor);
17
return (KotlinDetector.isKotlinType(ctor.getDeclaringClass()) ?
18
KotlinDelegate.instantiateClass(ctor, args) : ctor.newInstance(args));
19
}
20
catch (InstantiationException ex) {
21
throw new BeanInstantiationException(ctor, "Is it an abstract class?", ex);
22
}
23
catch (IllegalAccessException ex) {
24
throw new BeanInstantiationException(ctor, "Is the constructor accessible?", ex);
25
}
26
catch (IllegalArgumentException ex) {
27
throw new BeanInstantiationException(ctor, "Illegal arguments for constructor", ex);
28
}
29
catch (InvocationTargetException ex) {
30
throw new BeanInstantiationException(ctor, "Constructor threw exception", ex.getTargetException());
31
}
32
}
33
该方法会判断是否是 Kotlin 类型。如果不是，则调用构造器的实例方法。
到这里，我们的实例已经创建。但是我们的实例的依赖还没有设置，刚刚我们在 doCreateBean方法说关心以下2行代码：
instanceWrapper = createBeanInstance(beanName, mbd, args) 创建实例。
populateBean(beanName, mbd, instanceWrapper) ， 该方法用于填充Bean，该方法可以就是说就是发生依赖注入的地方。
我们已经解析了第一个，现在看第二个方法：
/**
* Populate the bean instance in the given BeanWrapper with the property values
* from the bean definition.
* @param beanName the name of the bean
* @param mbd the bean definition for the bean
* @param bw the BeanWrapper with bean instance
*/
protected void populateBean(String beanName, RootBeanDefinition mbd, @Nullable BeanWrapper bw) {
if (bw == null) {
if (mbd.hasPropertyValues()) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Cannot apply property values to null instance");
}
else {
// Skip property population phase for null instance.
return;
}
}
// Give any InstantiationAwareBeanPostProcessors the opportunity to modify the
// state of the bean before properties are set. This can be used, for example,
// to support styles of field injection.
boolean continueWithPropertyPopulation = true;
if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof InstantiationAwareBeanPostProcessor) {
InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {
continueWithPropertyPopulation = false;
break;
}
}
}
}
if (!continueWithPropertyPopulation) {
return;
}
PropertyValues pvs = (mbd.hasPropertyValues() ? mbd.getPropertyValues() : null);
if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME ||
mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {
MutablePropertyValues newPvs = new MutablePropertyValues(pvs);
// Add property values based on autowire by name if applicable.
if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME) {
autowireByName(beanName, mbd, bw, newPvs);
}
// Add property values based on autowire by type if applicable.
if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {
autowireByType(beanName, mbd, bw, newPvs);
}
pvs = newPvs;
}
boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors();
boolean needsDepCheck = (mbd.getDependencyCheck() != RootBeanDefinition.DEPENDENCY_CHECK_NONE);
if (hasInstAwareBpps || needsDepCheck) {
if (pvs == null) {
pvs = mbd.getPropertyValues();
}
PropertyDescriptor[] filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
if (hasInstAwareBpps) {
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof InstantiationAwareBeanPostProcessor) {
InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
pvs = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);
if (pvs == null) {
return;
}
}
}
}
if (needsDepCheck) {
checkDependencies(beanName, mbd, filteredPds, pvs);
}
}
if (pvs != null) {
applyPropertyValues(beanName, mbd, bw, pvs);
}
}
87
1
/**
2
* Populate the bean instance in the given BeanWrapper with the property values
3
* from the bean definition.
4
* @param beanName the name of the bean
5
* @param mbd the bean definition for the bean
6
* @param bw the BeanWrapper with bean instance
7
*/
8
protected void populateBean(String beanName, RootBeanDefinition mbd, BeanWrapper bw) {
9
if (bw == null) {
10
if (mbd.hasPropertyValues()) {
11
throw new BeanCreationException(
12
mbd.getResourceDescription(), beanName, "Cannot apply property values to null instance");
13
}
14
else {
15
// Skip property population phase for null instance.
16
return;
17
}
18
}
19
20
// Give any InstantiationAwareBeanPostProcessors the opportunity to modify the
21
// state of the bean before properties are set. This can be used, for example,
22
// to support styles of field injection.
23
boolean continueWithPropertyPopulation = true;
24
25
if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
26
for (BeanPostProcessor bp : getBeanPostProcessors()) {
27
if (bp instanceof InstantiationAwareBeanPostProcessor) {
28
InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
29
if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {
30
continueWithPropertyPopulation = false;
31
break;
32
}
33
}
34
}
35
}
36
37
if (!continueWithPropertyPopulation) {
38
return;
39
}
40
41
PropertyValues pvs = (mbd.hasPropertyValues() ? mbd.getPropertyValues() : null);
42
43
if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME ||
44
mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {
45
MutablePropertyValues newPvs = new MutablePropertyValues(pvs);
46
47
// Add property values based on autowire by name if applicable.
48
if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME) {
49
autowireByName(beanName, mbd, bw, newPvs);
50
}
51
52
// Add property values based on autowire by type if applicable.
53
if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {
54
autowireByType(beanName, mbd, bw, newPvs);
55
}
56
57
pvs = newPvs;
58
}
59
60
boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors();
61
boolean needsDepCheck = (mbd.getDependencyCheck() != RootBeanDefinition.DEPENDENCY_CHECK_NONE);
62
63
if (hasInstAwareBpps || needsDepCheck) {
64
if (pvs == null) {
65
pvs = mbd.getPropertyValues();
66
}
67
PropertyDescriptor[] filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
68
if (hasInstAwareBpps) {
69
for (BeanPostProcessor bp : getBeanPostProcessors()) {
70
if (bp instanceof InstantiationAwareBeanPostProcessor) {
71
InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
72
pvs = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);
73
if (pvs == null) {
74
return;
75
}
76
}
77
}
78
}
79
if (needsDepCheck) {
80
checkDependencies(beanName, mbd, filteredPds, pvs);
81
}
82
}
83
84
if (pvs != null) {
85
applyPropertyValues(beanName, mbd, bw, pvs);
86
}
87
}
该方法核心逻辑是
PropertyValues pvs = (mbd.hasPropertyValues() ? mbd.getPropertyValues() : null)，
即获取该bean的所有属性，也就是我们配置property元素。最后执行 applyPropertyValues(beanName, mbd, bw, pvs) 方法。
/**
* Apply the given property values, resolving any runtime references
* to other beans in this bean factory. Must use deep copy, so we
* don't permanently modify this property.
* @param beanName the bean name passed for better exception information
* @param mbd the merged bean definition
* @param bw the BeanWrapper wrapping the target object
* @param pvs the new property values
*/
protected void applyPropertyValues(String beanName, BeanDefinition mbd, BeanWrapper bw, PropertyValues pvs) {
if (pvs.isEmpty()) {
return;
}
if (System.getSecurityManager() != null && bw instanceof BeanWrapperImpl) {
((BeanWrapperImpl) bw).setSecurityContext(getAccessControlContext());
}
MutablePropertyValues mpvs = null;
List<PropertyValue> original;
if (pvs instanceof MutablePropertyValues) {
mpvs = (MutablePropertyValues) pvs;
if (mpvs.isConverted()) {
// Shortcut: use the pre-converted values as-is.
try {
bw.setPropertyValues(mpvs);
return;
}
catch (BeansException ex) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Error setting property values", ex);
}
}
original = mpvs.getPropertyValueList();
}
else {
original = Arrays.asList(pvs.getPropertyValues());
}
TypeConverter converter = getCustomTypeConverter();
if (converter == null) {
converter = bw;
}
BeanDefinitionValueResolver valueResolver = new BeanDefinitionValueResolver(this, beanName, mbd, converter);
// Create a deep copy, resolving any references for values.
List<PropertyValue> deepCopy = new ArrayList<>(original.size());
boolean resolveNecessary = false;
for (PropertyValue pv : original) {
if (pv.isConverted()) {
deepCopy.add(pv);
}
else {
String propertyName = pv.getName();
Object originalValue = pv.getValue();
Object resolvedValue = valueResolver.resolveValueIfNecessary(pv, originalValue);
Object convertedValue = resolvedValue;
boolean convertible = bw.isWritableProperty(propertyName) &&
!PropertyAccessorUtils.isNestedOrIndexedProperty(propertyName);
if (convertible) {
convertedValue = convertForProperty(resolvedValue, propertyName, bw, converter);
}
// Possibly store converted value in merged bean definition,
// in order to avoid re-conversion for every created bean instance.
if (resolvedValue == originalValue) {
if (convertible) {
pv.setConvertedValue(convertedValue);
}
deepCopy.add(pv);
}
else if (convertible && originalValue instanceof TypedStringValue &&
!((TypedStringValue) originalValue).isDynamic() &&
!(convertedValue instanceof Collection || ObjectUtils.isArray(convertedValue))) {
pv.setConvertedValue(convertedValue);
deepCopy.add(pv);
}
else {
resolveNecessary = true;
deepCopy.add(new PropertyValue(pv, convertedValue));
}
}
}
if (mpvs != null && !resolveNecessary) {
mpvs.setConverted();
}
// Set our (possibly massaged) deep copy.
try {
bw.setPropertyValues(new MutablePropertyValues(deepCopy));
}
catch (BeansException ex) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Error setting property values", ex);
}
}
96
1
/**
2
* Apply the given property values, resolving any runtime references
3
* to other beans in this bean factory. Must use deep copy, so we
4
* don't permanently modify this property.
5
* @param beanName the bean name passed for better exception information
6
* @param mbd the merged bean definition
7
* @param bw the BeanWrapper wrapping the target object
8
* @param pvs the new property values
9
*/
10
protected void applyPropertyValues(String beanName, BeanDefinition mbd, BeanWrapper bw, PropertyValues pvs) {
11
if (pvs.isEmpty()) {
12
return;
13
}
14
15
if (System.getSecurityManager() != null && bw instanceof BeanWrapperImpl) {
16
((BeanWrapperImpl) bw).setSecurityContext(getAccessControlContext());
17
}
18
19
MutablePropertyValues mpvs = null;
20
List<PropertyValue> original;
21
22
if (pvs instanceof MutablePropertyValues) {
23
mpvs = (MutablePropertyValues) pvs;
24
if (mpvs.isConverted()) {
25
// Shortcut: use the pre-converted values as-is.
26
try {
27
bw.setPropertyValues(mpvs);
28
return;
29
}
30
catch (BeansException ex) {
31
throw new BeanCreationException(
32
mbd.getResourceDescription(), beanName, "Error setting property values", ex);
33
}
34
}
35
original = mpvs.getPropertyValueList();
36
}
37
else {
38
original = Arrays.asList(pvs.getPropertyValues());
39
}
40
41
TypeConverter converter = getCustomTypeConverter();
42
if (converter == null) {
43
converter = bw;
44
}
45
BeanDefinitionValueResolver valueResolver = new BeanDefinitionValueResolver(this, beanName, mbd, converter);
46
47
// Create a deep copy, resolving any references for values.
48
List<PropertyValue> deepCopy = new ArrayList<>(original.size());
49
boolean resolveNecessary = false;
50
for (PropertyValue pv : original) {
51
if (pv.isConverted()) {
52
deepCopy.add(pv);
53
}
54
else {
55
String propertyName = pv.getName();
56
Object originalValue = pv.getValue();
57
Object resolvedValue = valueResolver.resolveValueIfNecessary(pv, originalValue);
58
Object convertedValue = resolvedValue;
59
boolean convertible = bw.isWritableProperty(propertyName) &&
60
!PropertyAccessorUtils.isNestedOrIndexedProperty(propertyName);
61
if (convertible) {
62
convertedValue = convertForProperty(resolvedValue, propertyName, bw, converter);
63
}
64
// Possibly store converted value in merged bean definition,
65
// in order to avoid re-conversion for every created bean instance.
66
if (resolvedValue == originalValue) {
67
if (convertible) {
68
pv.setConvertedValue(convertedValue);
69
}
70
deepCopy.add(pv);
71
}
72
else if (convertible && originalValue instanceof TypedStringValue &&
73
!((TypedStringValue) originalValue).isDynamic() &&
74
!(convertedValue instanceof Collection || ObjectUtils.isArray(convertedValue))) {
75
pv.setConvertedValue(convertedValue);
76
deepCopy.add(pv);
77
}
78
else {
79
resolveNecessary = true;
80
deepCopy.add(new PropertyValue(pv, convertedValue));
81
}
82
}
83
}
84
if (mpvs != null && !resolveNecessary) {
85
mpvs.setConverted();
86
}
87
88
// Set our (possibly massaged) deep copy.
89
try {
90
bw.setPropertyValues(new MutablePropertyValues(deepCopy));
91
}
92
catch (BeansException ex) {
93
throw new BeanCreationException(
94
mbd.getResourceDescription(), beanName, "Error setting property values", ex);
95
}
96
}
注意，现在的PropertyValues 都是字符串，没有值的，这个方法的作用就是获取值，关键代码：
Object resolvedValue = valueResolver.resolveValueIfNecessary(pv, originalValue)
该方法会获取 pvName 所对应的容器value，该方法内部会调用 BeanWrapperImpl的resolveReference(argName, ref) 方法，我们看看该方法：
/**
* Resolve a reference to another bean in the factory.
*/
@Nullable
private Object resolveReference(Object argName, RuntimeBeanReference ref) {
try {
Object bean;
String refName = ref.getBeanName();
refName = String.valueOf(doEvaluate(refName));
if (ref.isToParent()) {
if (this.beanFactory.getParentBeanFactory() == null) {
throw new BeanCreationException(
this.beanDefinition.getResourceDescription(), this.beanName,
"Can't resolve reference to bean '" + refName +
"' in parent factory: no parent factory available");
}
bean = this.beanFactory.getParentBeanFactory().getBean(refName);
}
else {
bean = this.beanFactory.getBean(refName);
this.beanFactory.registerDependentBean(refName, this.beanName);
}
if (bean instanceof NullBean) {
bean = null;
}
return bean;
}
catch (BeansException ex) {
throw new BeanCreationException(
this.beanDefinition.getResourceDescription(), this.beanName,
"Cannot resolve reference to bean '" + ref.getBeanName() + "' while setting " + argName, ex);
}
}
1
33
1
/**
2
* Resolve a reference to another bean in the factory.
3
*/
4
5
private Object resolveReference(Object argName, RuntimeBeanReference ref) {
6
try {
7
Object bean;
8
String refName = ref.getBeanName();
9
refName = String.valueOf(doEvaluate(refName));
10
if (ref.isToParent()) {
11
if (this.beanFactory.getParentBeanFactory() == null) {
12
throw new BeanCreationException(
13
this.beanDefinition.getResourceDescription(), this.beanName,
14
"Can't resolve reference to bean '" + refName +
15
"' in parent factory: no parent factory available");
16
}
17
bean = this.beanFactory.getParentBeanFactory().getBean(refName);
18
}
19
else {
20
bean = this.beanFactory.getBean(refName);
21
this.beanFactory.registerDependentBean(refName, this.beanName);
22
}
23
if (bean instanceof NullBean) {
24
bean = null;
25
}
26
return bean;
27
}
28
catch (BeansException ex) {
29
throw new BeanCreationException(
30
this.beanDefinition.getResourceDescription(), this.beanName,
31
"Cannot resolve reference to bean '" + ref.getBeanName() + "' while setting " + argName, ex);
32
}
33
}
其中有一行熟悉的代码：bean = this.beanFactory.getBean(refName)，对，这里就是发生递归的地方。该方法会拿着属性名称从容器中获取实例。
我们回到 applyPropertyValues 方法。此时deepCopy 集合已经有值了，不再仅仅是字符串了。
然后调用 setPropertyValues(new MutablePropertyValues(deepCopy)) 方法， 该方法会调用 AbstractPropertyAccessor.setPropertyValues 方法完成注入，而该方法会循环元素列表， 循环中调用 setPropertyValue(PropertyValue pv) 方法， 该方法
setPropertyValue(PropertyValue pv)最后会调用 nestedPa.setPropertyValue(tokens, pv) 方法， 该方法又会调用 processLocalProperty(tokens, pv) 方法，该方法最后又会调用 ph.setValue(valueToApply) 方法，也就是BeanWrapperImpl.setValue() 方法，终于，我们要看到反射了，看到反射说明到了尽头。
@Override
public void setValue(final @Nullable Object value) throws Exception {
final Method writeMethod = (this.pd instanceof GenericTypeAwarePropertyDescriptor ?
((GenericTypeAwarePropertyDescriptor) this.pd).getWriteMethodForActualAccess() :
this.pd.getWriteMethod());
if (System.getSecurityManager() != null) {
AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
ReflectionUtils.makeAccessible(writeMethod);
return null;
});
try {
AccessController.doPrivileged((PrivilegedExceptionAction<Object>) () ->
writeMethod.invoke(getWrappedInstance(), value), acc);
}
catch (PrivilegedActionException ex) {
throw ex.getException();
}
}
else {
ReflectionUtils.makeAccessible(writeMethod);
writeMethod.invoke(getWrappedInstance(), value);
}
}
}
1
24
1
2
public void setValue(final Object value) throws Exception {
3
final Method writeMethod = (this.pd instanceof GenericTypeAwarePropertyDescriptor ?
4
((GenericTypeAwarePropertyDescriptor) this.pd).getWriteMethodForActualAccess() :
5
this.pd.getWriteMethod());
6
if (System.getSecurityManager() != null) {
7
AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
8
ReflectionUtils.makeAccessible(writeMethod);
9
return null;
10
});
11
try {
12
AccessController.doPrivileged((PrivilegedExceptionAction<Object>) () ->
13
writeMethod.invoke(getWrappedInstance(), value), acc);
14
}
15
catch (PrivilegedActionException ex) {
16
throw ex.getException();
17
}
18
}
19
else {
20
ReflectionUtils.makeAccessible(writeMethod);
21
writeMethod.invoke(getWrappedInstance(), value);
22
}
23
}
24
}