寻找spring框架的启动入口 ContextLoaderListener

spring在web下的入口在配置文件web.xml的监听器中

<listener>

??????? <listener-class>

?????????? org.springframework.web.context.ContextLoaderListener

??????? </listener-class>

</listener>

<context-param>

???? <param-name>contextConfigLocation</param-name>

????? <param-value>classpath:conf/spring/applicationContext.xml</param-value>

</context-param>

上述是在web.xml中的配置信息。

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//实现了接口ServletContextListener,也就是说他必须实现contextDestroyed, contextInitialized这两个方法

public class ContextLoaderListener implements ServletContextListener {

?????? private ContextLoader contextLoader;

?????? /**

?????? * Initialize the root web application context.

?????? */

//Spring框架由此启动, contextInitialized也就是监听器类的main入口函数

?????? public void contextInitialized(ServletContextEvent event) {

????????????? this.contextLoader = createContextLoader();

????????????? this.contextLoader.initWebApplicationContext(event.getServletContext());

?????? }

?????? /**

?????? * Create the ContextLoader to use. Can be overridden in subclasses.

?????? * @return the new ContextLoader

?????? */?? ?????????????????????????????????????????

?????? protected ContextLoader createContextLoader() {

????????????? return new ContextLoader();

?????? }

?????? /**

?????? * Return the ContextLoader used by this listener.

?????? * @return the current ContextLoader

?????? */

?????? public ContextLoader getContextLoader() {

????????????? return this.contextLoader;

?????? }

?????? /**

?????? * Close the root web application context.

?????? */

?????? public void contextDestroyed(ServletContextEvent event) {

????????????? if (this.contextLoader != null) {

???????????????????? this.contextLoader.closeWebApplicationContext(event.getServletContext());

????????????? }

?????? }

}

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总的来说这个入口非常简单,所有实现都隐藏在ContextLoader类里,我们在下一篇的内容中讨论ContextLoader,如果你不知道为什么这里是程序的入口,那么复习一下ServletContextListener 接口和监听器的相关知识吧