spring源码之IOC的依赖注入

其他 2018-08-19 16:44:22 阅读次数: 0

 

前言

上一篇对启动时的整个流程进行了大体的分析，这一篇ioc的核心部分进行分析。包括初始化过程和依赖注入过程。

概述

在分析之前先看几个类图

DefaultListableBeanFactory是ioc的一个核心类，可以看到我们关心的bean定义和单例bean都注册在它的属性上。

ClassPathXmlApplicationContext注意一下，它实现了事件发布、资源解析、消息源、资源加载的几个接口。

ClassPathXmlApplicationContext实现了资源加载接口，可以把xml配置的信息加载到Resource对象中。

XmlBeanDefinitionReader把Resouce中的内容读到Document对象中

DefaultBeanDefinitionDocumentReader负责把读取Document内容转化成BeanDefinition对象

源码分析之初始化过程

  • 接着上篇的源码进行分析，直接来到在AbstractApplicationContext类的refresh方法中调用的obtainFreshBeanFactory方法。这个方法是我们初始化过程的入口。这个方法做了三件事
    • 创建一个DefaultListableBeanFactory
    • 把配置文件中的bean定义转换成BeanDefintion对象并注册到DefaultListableBeanFactory上
    • 返回这个DefaultListabelBeanFactory对象　　
//AbstractApplicationContext类的方法
//创建并返回DefaultListableBeanFactory
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
    refreshBeanFactory();
    ConfigurableListableBeanFactory beanFactory = getBeanFactory();
    if (logger.isDebugEnabled()) {
        logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);
    }
    return beanFactory;
}
  • 刷新beanFactory，这个方法主要分为四步，我们关心的是第二步和第四步
    • 如果之前已经有创建过beanFactory，那么这里会对注册在它上面的bean进行销毁，并关闭这个beanFactory
    • 创建一个beanFactory，这个就是去创建一个DefaultListBeanFactory
    • 一些对beanFactory的自定义处理，这里设置了bean定义是否可以重写，是否可以循环引用
    • 最后，也是最重要的，加载bean定义　　
//AbstractRefreshableApplicationContext类的方法
protected final void refreshBeanFactory() throws BeansException {
    if (hasBeanFactory()) {
        destroyBeans();
        closeBeanFactory();
    }
    try {
        DefaultListableBeanFactory beanFactory = createBeanFactory();
        beanFactory.setSerializationId(getId());
        customizeBeanFactory(beanFactory);
        loadBeanDefinitions(beanFactory);
        synchronized (this.beanFactoryMonitor) {
            this.beanFactory = beanFactory; } } catch (IOException ex) { throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex); } }
  • 加载bean定义，这里主要做了三件事。在这里我们看到了创建了一个XmlBeanDefinitionReader对象
    • 创建XmlBeanDefinitionReader对象
    • 进行一些设置和加载前的处理
    • 加载bean定义，继续向下委派
//AbstractXmlApplicationContext类的方法
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);
}
  • 拿到Resource对象，整个过程如下
    • 如果是Resource对象，则直接加载。但由于我们这里是路径，先对每一个路径进行循环
    • 拿到ResourceLoader，当前ClassPathXmlApplicationContext对象就是并且它实现了ResourcePatternResolver接口，那么用当前的上下文对象把定义路径上的xml文件读取到Resource对象中
    • XmlBeanDefinitionReader掊下来再对Resource对象进行加载　　
//AbstractXmlApplicationContext类的方法
protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException {
    Resource[] configResources = getConfigResources();
    if (configResources != null) {
        reader.loadBeanDefinitions(configResources);
    }
    String[] configLocations = getConfigLocations();
    if (configLocations != null) {
        reader.loadBeanDefinitions(configLocations);
    }
}

//AbstractBeanDefinitionReader类的方法
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; } 
//AbstractBeanDefinitonReader类的方法 public int loadBeanDefinitions(String location) throws BeanDefinitionStoreException { return loadBeanDefinitions(location, null); } 
//AbstractBeanDefinitionReader类的方法 public int loadBeanDefinitions(String location, Set<Resource> actualResources) throws BeanDefinitionStoreException { 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 { Resource[] resources = ((ResourcePatternResolver) resourceLoader).getResources(location); 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; } }
  • 把Resource对象封装成InputSource对象
//AbstractBeanDefinitionReader类的方法
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; }
 //XmlBeanDefinitionReader类的方法 public int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException { return loadBeanDefinitions(new EncodedResource(resource)); } 
//XmlBeanDefintionReader类的方法 public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException { Assert.notNull(encodedResource, "EncodedResource must not be null"); if (logger.isInfoEnabled()) { logger.info("Loading XML bean definitions from " + encodedResource.getResource()); } //使用ThreadLocal，实现随用随取 Set<EncodedResource> currentResources = this.resourcesCurrentlyBeingLoaded.get(); if (currentResources == null) { currentResources = new HashSet<EncodedResource>(4); this.resourcesCurrentlyBeingLoaded.set(currentResources); } //判断资源文件有没有重复载入 if (!currentResources.add(encodedResource)) { throw new BeanDefinitionStoreException( "Detected cyclic loading of " + encodedResource + " - check your import definitions!"); } try { InputStream inputStream = encodedResource.getResource().getInputStream(); try { InputSource inputSource = new InputSource(inputStream); if (encodedResource.getEncoding() != null) { inputSource.setEncoding(encodedResource.getEncoding()); } return doLoadBeanDefinitions(inputSource, encodedResource.getResource()); } finally { inputStream.close(); } } catch (IOException ex) { throw new BeanDefinitionStoreException( "IOException parsing XML document from " + encodedResource.getResource(), ex); } finally { currentResources.remove(encodedResource); if (currentResources.isEmpty()) { this.resourcesCurrentlyBeingLoaded.remove(); } } }
  • 通过DefaultDocumentLoader把InputSource对象读取到Document对象中
//XmlBeanDefinitionReader类的方法
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); } }
  • 创建BeanDefintionDocumentReader对象，这里创建的是DefaultBeanDefiniitonDocumentReader对象
public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {
    BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();
    int countBefore = getRegistry().getBeanDefinitionCount();
    documentReader.registerBeanDefinitions(doc, createReaderContext(resource));
    return getRegistry().getBeanDefinitionCount() - countBefore;
}
  • 获取合适的解析器。创建一个BeanDefintionParserDelegate对象，这个对象可以帮助找到合适解析器，在AOP的分析中有说到，这里不说明。对于bean命名空间下的，会走默认的元素解析。 这里我们可以先看到对profile标签进行了解析
//DefaultBeanDefintionDocumentReader类的方法
public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {
    this.readerContext = readerContext;
    logger.debug("Loading bean definitions");
    Element root = doc.getDocumentElement();
    doRegisterBeanDefinitions(root);
}

//DefaultBeanDefintionDocumentReader类的方法
protected void doRegisterBeanDefinitions(Element root) {
    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; } 
//DefaultBeanDefintioinDocumentReader类的方法 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); } }
  • 这里我们看到了对我们常用的import，alias，bean，beans进行了解析。现在我们着重看下对bean的解析
//DefaultBeanDefintionDocumentReader类的方法
private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) {
    if (delegate.nodeNameEquals(ele, IMPORT_ELEMENT)) {
        importBeanDefinitionResource(ele);
    }
    else if (delegate.nodeNameEquals(ele, ALIAS_ELEMENT)) {
        processAliasRegistration(ele);
    }
    else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) {
        processBeanDefinition(ele, delegate);
    }
    else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) {
        // recurse
 doRegisterBeanDefinitions(ele); } }
  • bean标签的解析，这里很显然的两步
    • 解析element得到BeanDefinitionHolder
    • 注册BeanDefintion
//DefaultBeanDefintionDocumentReader类的方法
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
    BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
    if (bdHolder != null) {
        bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
        try {
            // Register the final decorated instance.
            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)); } }
  •  解析得到BeanDefintionHolder，下面的所有代码都是BeanDefintionParserDelegate类的方法，这个过程就是对<bean>标签及下面的字节点进行解析，并设置到BeanDefintion中去，返回一个BeanDefintionHolder。

　　BeanDefinitonHolder中有BeanDefiniton、beanName以及bean的别名数组。

public BeanDefinitionHolder parseBeanDefinitionElement(Element ele) {
    return parseBeanDefinitionElement(ele, null);
}

public BeanDefinitionHolder parseBeanDefinitionElement(Element ele, BeanDefinition containingBean) {
    String id = ele.getAttribute(ID_ATTRIBUTE);
    String nameAttr = ele.getAttribute(NAME_ATTRIBUTE);

    List<String> aliases = new ArrayList<String>(); if (StringUtils.hasLength(nameAttr)) { String[] nameArr = StringUtils.tokenizeToStringArray(nameAttr, MULTI_VALUE_ATTRIBUTE_DELIMITERS); aliases.addAll(Arrays.asList(nameArr)); } String beanName = id; if (!StringUtils.hasText(beanName) && !aliases.isEmpty()) { beanName = aliases.remove(0); if (logger.isDebugEnabled()) { logger.debug("No XML 'id' specified - using '" + beanName + "' as bean name and " + aliases + " as aliases"); } } if (containingBean == null) { checkNameUniqueness(beanName, aliases, ele); } AbstractBeanDefinition beanDefinition = parseBeanDefinitionElement(ele, beanName, containingBean); if (beanDefinition != null) { if (!StringUtils.hasText(beanName)) { try { if (containingBean != null) { beanName = BeanDefinitionReaderUtils.generateBeanName( beanDefinition, this.readerContext.getRegistry(), true); } else { beanName = this.readerContext.generateBeanName(beanDefinition); // Register an alias for the plain bean class name, if still possible, // if the generator returned the class name plus a suffix. // This is expected for Spring 1.2/2.0 backwards compatibility. String beanClassName = beanDefinition.getBeanClassName(); if (beanClassName != null && beanName.startsWith(beanClassName) && beanName.length() > beanClassName.length() && !this.readerContext.getRegistry().isBeanNameInUse(beanClassName)) { aliases.add(beanClassName); } } if (logger.isDebugEnabled()) { logger.debug("Neither XML 'id' nor 'name' specified - " + "using generated bean name [" + beanName + "]"); } } catch (Exception ex) { error(ex.getMessage(), ele); return null; } } String[] aliasesArray = StringUtils.toStringArray(aliases); return new BeanDefinitionHolder(beanDefinition, beanName, aliasesArray); } return null; } public AbstractBeanDefinition parseBeanDefinitionElement( Element ele, String beanName, BeanDefinition containingBean) { this.parseState.push(new BeanEntry(beanName)); String className = null; if (ele.hasAttribute(CLASS_ATTRIBUTE)) { className = ele.getAttribute(CLASS_ATTRIBUTE).trim(); } try { String parent = null; if (ele.hasAttribute(PARENT_ATTRIBUTE)) { parent = ele.getAttribute(PARENT_ATTRIBUTE); } 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; } public void parsePropertyElements(Element beanEle, BeanDefinition bd) { NodeList nl = beanEle.getChildNodes(); for (int i = 0; i < nl.getLength(); i++) { Node node = nl.item(i); if (isCandidateElement(node) && nodeNameEquals(node, PROPERTY_ELEMENT)) { parsePropertyElement((Element) node, bd); } } } public void parsePropertyElement(Element ele, BeanDefinition bd) { String propertyName = ele.getAttribute(NAME_ATTRIBUTE); if (!StringUtils.hasLength(propertyName)) { error("Tag 'property' must have a 'name' attribute", ele); return; } this.parseState.push(new PropertyEntry(propertyName)); try { if (bd.getPropertyValues().contains(propertyName)) { error("Multiple 'property' definitions for property '" + propertyName + "'", ele); return; } Object val = parsePropertyValue(ele, bd, propertyName); PropertyValue pv = new PropertyValue(propertyName, val); parseMetaElements(ele, pv); pv.setSource(extractSource(ele)); bd.getPropertyValues().addPropertyValue(pv); } finally { this.parseState.pop(); } } public Object parsePropertyValue(Element ele, BeanDefinition bd, String propertyName) { String elementName = (propertyName != null) ? "<property> element for property '" + propertyName + "'" : "<constructor-arg> element"; // Should only have one child element: ref, value, list, etc. NodeList nl = ele.getChildNodes(); Element subElement = null; for (int i = 0; i < nl.getLength(); i++) { Node node = nl.item(i); if (node instanceof Element && !nodeNameEquals(node, DESCRIPTION_ELEMENT) && !nodeNameEquals(node, META_ELEMENT)) { // Child element is what we're looking for. if (subElement != null) { error(elementName + " must not contain more than one sub-element", ele); } else { subElement = (Element) node; } } } boolean hasRefAttribute = ele.hasAttribute(REF_ATTRIBUTE); boolean hasValueAttribute = ele.hasAttribute(VALUE_ATTRIBUTE); if ((hasRefAttribute && hasValueAttribute) || ((hasRefAttribute || hasValueAttribute) && subElement != null)) { error(elementName + " is only allowed to contain either 'ref' attribute OR 'value' attribute OR sub-element", ele); } if (hasRefAttribute) { String refName = ele.getAttribute(REF_ATTRIBUTE); if (!StringUtils.hasText(refName)) { error(elementName + " contains empty 'ref' attribute", ele); } RuntimeBeanReference ref = new RuntimeBeanReference(refName); ref.setSource(extractSource(ele)); return ref; } else if (hasValueAttribute) { TypedStringValue valueHolder = new TypedStringValue(ele.getAttribute(VALUE_ATTRIBUTE)); valueHolder.setSource(extractSource(ele)); return valueHolder; } else if (subElement != null) { return parsePropertySubElement(subElement, bd); } else { // Neither child element nor "ref" or "value" attribute found. error(elementName + " must specify a ref or value", ele); return null; } } public Object parsePropertySubElement(Element ele, BeanDefinition bd) { return parsePropertySubElement(ele, bd, null); } public Object parsePropertySubElement(Element ele, BeanDefinition bd, String defaultValueType) { if (!isDefaultNamespace(ele)) { return parseNestedCustomElement(ele, bd); } else if (nodeNameEquals(ele, BEAN_ELEMENT)) { BeanDefinitionHolder nestedBd = parseBeanDefinitionElement(ele, bd); if (nestedBd != null) { nestedBd = decorateBeanDefinitionIfRequired(ele, nestedBd, bd); } return nestedBd; } else if (nodeNameEquals(ele, REF_ELEMENT)) { // A generic reference to any name of any bean. String refName = ele.getAttribute(BEAN_REF_ATTRIBUTE); boolean toParent = false; if (!StringUtils.hasLength(refName)) { // A reference to the id of another bean in the same XML file. refName = ele.getAttribute(LOCAL_REF_ATTRIBUTE); if (!StringUtils.hasLength(refName)) { // A reference to the id of another bean in a parent context. refName = ele.getAttribute(PARENT_REF_ATTRIBUTE); toParent = true; if (!StringUtils.hasLength(refName)) { error("'bean', 'local' or 'parent' is required for <ref> element", ele); return null; } } } if (!StringUtils.hasText(refName)) { error("<ref> element contains empty target attribute", ele); return null; } RuntimeBeanReference ref = new RuntimeBeanReference(refName, toParent); ref.setSource(extractSource(ele)); return ref; } else if (nodeNameEquals(ele, IDREF_ELEMENT)) { return parseIdRefElement(ele); } else if (nodeNameEquals(ele, VALUE_ELEMENT)) { return parseValueElement(ele, defaultValueType); } else if (nodeNameEquals(ele, NULL_ELEMENT)) { // It's a distinguished null value. Let's wrap it in a TypedStringValue // object in order to preserve the source location. TypedStringValue nullHolder = new TypedStringValue(null); nullHolder.setSource(extractSource(ele)); return nullHolder; } else if (nodeNameEquals(ele, ARRAY_ELEMENT)) { return parseArrayElement(ele, bd); } else if (nodeNameEquals(ele, LIST_ELEMENT)) { return parseListElement(ele, bd); } else if (nodeNameEquals(ele, SET_ELEMENT)) { return parseSetElement(ele, bd); } else if (nodeNameEquals(ele, MAP_ELEMENT)) { return parseMapElement(ele, bd); } else if (nodeNameEquals(ele, PROPS_ELEMENT)) { return parsePropsElement(ele); } else { error("Unknown property sub-element: [" + ele.getNodeName() + "]", ele); return null; } }
  •  注册过程，关于registry，可以看到是由getReaderContext().getRegistry()，可以回过去看下new XmlBeanDefintionReader（），传入一个DefaultListableBeanFactory(也就是我们创建出来的bean工厂)。所有我们这里的registry就是之前创建的DefaultListableBeanFactory对象。可以进去这个两个方法看到
    • 注册beanName与BeanDefiniton的映射到DefaultListableBeanFactory的一个属性名为beanDefinitionMap类型为ConcurrentHashMap上
    • 注册beanName与别名映射到SimpleAliasRegistry的属性名为aliasMap类型为ConcurrentHashMap上　　
//BeanDefinitonReaderUtils
public static void registerBeanDefinition(
        BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
        throws BeanDefinitionStoreException {

    // Register bean definition under primary name.
    String beanName = definitionHolder.getBeanName();
    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);
        }
    }
}

总结

整个过程可以分为：

  • 创建DefaultListableBeanFactory对象
  • 创建XmlBeanDefinitionReader对象
  • XmlBeanDefinitionReader完成定位、解析、注册的工作
    • 通过ClassPathXmlApplicationContext上下文把xml文件读取Resource对象中（定位）
    • 把Resource对象转换成InputSource对象
    • 通过DefaultDocumentLoader把InputSource转换成Document对象
    • 解析Document到BeanDefinition、注册BeanDefinition到DefaultListableBeanFactory
      • 创建DefaultBeanDefinitonDocumentReader读document对象
      • 通过DefaultBeanDefinitonDocumentReader进行解析注册
        • 创建BeanDefinitionParserDelegate对象
        • 解析注册
          • BeanDefinitionParserDelegate负责对document到beanDefinition的解析
          • BeanDefinitionReaderUtils的registerBeanDefinition方法把解析好的beanDefinition注册到DefaultListableBeanFactory的concurrentHashMap上

参考链接

https://www.cnblogs.com/niejunlei/archive/2016/11/11/6054713.html(prepareBeanFactory)

https://www.cnblogs.com/wade-luffy/p/6074088.html(生命周期后置处理器)

https://blog.csdn.net/zhangduilei/article/details/76172355(注册JMX)

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