前言
从本篇文章开始主要介绍spring源码解析相关的spring上下文初始化、bean定义解析、beanFactory创建、初始化、bean定义注册到beanFactory、bean实例化、依赖注入流程中相关的步骤，由于spring源码体系比较庞大，本次主要是跟着程序加载顺序整理，遇到相关关键知识点会单独出来一篇文章，之道这个整个链路顺序解析完毕，后面spring源码合集整理的时候会按照模块进行归类梳理。
正文
本次主要从ContextLoaderListener这个入口进行跟踪源码，进行spring的源码解析。
先简单看下主要的类图
1bean定义解析相关
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2spring上下文相关
3beanProcessor相关
beanProcessors对bean的过程管理抽象。
3spring容器加载
跟踪这个方法
org.springframework.web.context.ContextLoaderListener#contextInitialized
servlet监听器初始时会加载初始化web应用程序上下文这个方法
@Override
public void contextInitialized(ServletContextEvent event) {
initWebApplicationContext(event.getServletContext());
}
跟踪这个方法
org.springframework.web.context.ContextLoader#initWebApplicationContext
public WebApplicationContext initWebApplicationContext(ServletContext servletContext) {
// web上下文是放在servlet上下文中的
if (servletContext.getAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE) != null) {
throw new IllegalStateException(
"Cannot initialize context because there is already a root application context present - " +
"check whether you have multiple ContextLoader* definitions in your web.xml!");
}
Log logger = LogFactory.getLog(ContextLoader.class);
servletContext.log("Initializing Spring root WebApplicationContext");
if (logger.isInfoEnabled()) {
logger.info("Root WebApplicationContext: initialization started");
}
long startTime = System.currentTimeMillis();
try {
// Store context in local instance variable, to guarantee that
// it is available on ServletContext shutdown.
// 初始化web程序上下文
if (this.context == null) {
this.context = createWebApplicationContext(servletContext);
}
if (this.context instanceof ConfigurableWebApplicationContext) {
ConfigurableWebApplicationContext cwac = (ConfigurableWebApplicationContext) this.context;
if (!cwac.isActive()) {
// The context has not yet been refreshed -> provide services such as
// setting the parent context, setting the application context id, etc
if (cwac.getParent() == null) {
// The context instance was injected without an explicit parent ->
// determine parent for root web application context, if any.
ApplicationContext parent = loadParentContext(servletContext);
// 设置上下文的父类
cwac.setParent(parent);
}
// 配置装载和刷新web上下文
configureAndRefreshWebApplicationContext(cwac, servletContext);
}
}
servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, this.context);
ClassLoader ccl = Thread.currentThread().getContextClassLoader();
if (ccl == ContextLoader.class.getClassLoader()) {
currentContext = this.context;
}
else if (ccl != null) {
currentContextPerThread.put(ccl, this.context);
}
if (logger.isDebugEnabled()) {
logger.debug("Published root WebApplicationContext as ServletContext attribute with name [" +
WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE + "]");
}
if (logger.isInfoEnabled()) {
long elapsedTime = System.currentTimeMillis() - startTime;
logger.info("Root WebApplicationContext: initialization completed in " + elapsedTime + " ms");
}
return this.context;
}
catch (RuntimeException ex) {
logger.error("Context initialization failed", ex);
servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, ex);
throw ex;
}
catch (Error err) {
logger.error("Context initialization failed", err);
servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, err);
throw err;
}
}
从这里可以看出web上下文是存储在servlet上下文中的，key值是
webApplicationContext.ROOT。
开始初始化web程序上下文
if (this.context == null) {
this.context = createWebApplicationContext(servletContext);
}
跟踪这个方法
org.springframework.web.context.ContextLoader#createWebApplicationContext
创建web应用上下文
protected WebApplicationContext createWebApplicationContext(ServletContext sc) {
Class<?> contextClass = determineContextClass(sc);
// 如果上下文的类型和ConfigurableWebApplicationContext类型不一致
if (!ConfigurableWebApplicationContext.class.isAssignableFrom(contextClass)) {
throw new ApplicationContextException("Custom context class [" + contextClass.getName() +
"] is not of type [" + ConfigurableWebApplicationContext.class.getName() + "]");
}
// 返回配置上下文对象
return (ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClass);
}
返回到这个方法
org.springframework.web.context.ContextLoader#initWebApplicationContext
if (cwac.getParent() == null) {
判断上下文是否是活动的，上下文刷新过一次，还没有关闭。
进入到这个方法，配置装载和刷新web上下文
org.springframework.web.context.ContextLoader#configureAndRefreshWebApplicationContext
// 配置和刷新web上下文
protected void configureAndRefreshWebApplicationContext(ConfigurableWebApplicationContext wac, ServletContext sc) {
if (ObjectUtils.identityToString(wac).equals(wac.getId())) {
// The application context id is still set to its original default value
// -> assign a more useful id based on available information
// 从配置中获取上下文的id
String idParam = sc.getInitParameter(CONTEXT_ID_PARAM);
if (idParam != null) {
wac.setId(idParam);
}
else {
// Generate default id... 生成上下文id字符串 webApplicationContext:+servlet.getContextPath()
wac.setId(ConfigurableWebApplicationContext.APPLICATION_CONTEXT_ID_PREFIX +
ObjectUtils.getDisplayString(sc.getContextPath()));
}
}
wac.setServletContext(sc);
// 获取配置文件路径 contextConfigLocation，配置文件可以是多个的，用，换行分开，可以用占位符
String configLocationParam = sc.getInitParameter(CONFIG_LOCATION_PARAM);
if (configLocationParam != null) {
wac.setConfigLocation(configLocationParam);
}
// The wac environment's #initPropertySources will be called in any case when the context
// is refreshed; do it eagerly here to ensure servlet property sources are in place for
// use in any post-processing or initialization that occurs below prior to #refresh
ConfigurableEnvironment env = wac.getEnvironment();
if (env instanceof ConfigurableWebEnvironment) {
((ConfigurableWebEnvironment) env).initPropertySources(sc, null);
}
// 加载子类实现的上下文
customizeContext(sc, wac);
// 上下文刷新
wac.refresh();
}
获取配置文件路径 contextConfigLocation，配置文件可以是多个的，用，换行分开，可以用占位符
String configLocationParam = sc.getInitParameter(CONFIG_LOCATION_PARAM);
// 加载子类实现的上下文 customizeContext(sc, wac);
org.springframework.web.context.ContextLoader#customizeContext 上下文初始化器找到具体要初始化的上下文类进行初始化
protected void customizeContext(ServletContext sc, ConfigurableWebApplicationContext wac) {
List<Class<ApplicationContextInitializer<ConfigurableApplicationContext>>> initializerClasses =
determineContextInitializerClasses(sc);
for (Class<ApplicationContextInitializer<ConfigurableApplicationContext>> initializerClass : initializerClasses) {
Class<?> initializerContextClass =
GenericTypeResolver.resolveTypeArgument(initializerClass, ApplicationContextInitializer.class);
if (initializerContextClass != null && !initializerContextClass.isInstance(wac)) {
throw new ApplicationContextException(String.format(
"Could not apply context initializer [%s] since its generic parameter [%s] " +
"is not assignable from the type of application context used by this " +
"context loader: [%s]", initializerClass.getName(), initializerContextClass.getName(),
wac.getClass().getName()));
}
this.contextInitializers.add(BeanUtils.instantiateClass(initializerClass));
}
AnnotationAwareOrderComparator.sort(this.contextInitializers);
for (ApplicationContextInitializer<ConfigurableApplicationContext> initializer : this.contextInitializers) {
initializer.initialize(wac);
}
}
最后
本次介绍到这里，以上内容仅供参考。
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