Spring ContextLoaderListener源码分析 - JAVA

当我们要自动装配ApplicationContext配置信息时候，首先在web.xml配置ContextLoaderListener，下面是部分源代码：
[java]
public class ContextLoaderListener implements ServletContextListener {

private ContextLoader contextLoader;

/**
* Initialize the root web application context.
*/
public void contextInitialized(ServletContextEvent event) {
this.contextLoader = createContextLoader();
this.contextLoader.initWebApplicationContext(event.getServletContext());//注意此处
}

protected ContextLoader createContextLoader() {
return new ContextLoader();
}

public ContextLoader getContextLoader() {
return this.contextLoader;
}

public void contextDestroyed(ServletContextEvent event) {
if (this.contextLoader != null) {
this.contextLoader.closeWebApplicationContext(event.getServletContext());
}
}

}
我们主要了解下WebApplicationContext是怎么初始化出来的，首先contextInitialized(ServletContextEvent event)方法的this.contextLoader.initWebApplicationContext(event.getServletContext());进去之后我们看到
[java]
public WebApplicationContext initWebApplicationContext(ServletContext servletContext)
throws IllegalStateException, BeansException {

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!");
}

servletContext.log("Initializing Spring root WebApplicationContext");
if (logger.isInfoEnabled()) {
logger.info("Root WebApplicationContext: initialization started");
}
long startTime = System.currentTimeMillis();

try {
// Determine parent for root web application context, if any.
ApplicationContext parent = loadParentContext(servletContext);

// Store context in local instance variable, to guarantee that
// it is available on ServletContext shutdown.
this.context = createWebApplicationContext(servletContext, parent);
servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, this.context);//注意此处
currentContextPerThread.put(Thread.currentThread().getContextClassLoader(), 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(WebApplication

Spring ContextLoaderListener源码分析(一)