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