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。

//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());

}

}

}

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