每日一则JavaWeb---Spring之ContextLoaderListener

首先这些接口全部来自于4.1版本的spring-web.jar包

package org.springframework.web.context;

先看一下ContextLoaderListener的继承结构

public class ContextLoaderListener extends ContextLoader implements ServletContextListener

可以看到其中涉及了ContextLoader、ServletContextListener。

首先看看ServletContextListener的源码，很简单：

public interface ServletContextListener extends EventListener {     public void contextInitialized(ServletContextEvent sce);    public void contextDestroyed(ServletContextEvent sce);}

也就是说容器初始化和容器关闭的时候会做一些事情，其中的参数ServletContextEvent也比较简单，就是将ServletContext序列化而且包了一层

public class ServletContextEvent extends java.util.EventObject { /** Construct a ServletContextEvent from the given context. * * @param source - the ServletContext that is sending the event. */    public ServletContextEvent(ServletContext source) {super(source);    }    /** * Return the ServletContext that changed. * * @return the ServletContext that sent the event. */    public ServletContext getServletContext () { return (ServletContext) super.getSource();    }    }

其中EventObject是就是把Object包了一层序列化的东西，当然哈重写了toString

public class EventObject implements java.io.Serializable {    private static final long serialVersionUID = 5516075349620653480L;    /**     * The object on which the Event initially occurred.     */    protected transient Object  source;    /**     * Constructs a prototypical Event.     *     * @param    source    The object on which the Event initially occurred.     * @exception  IllegalArgumentException  if source is null.     */    public EventObject(Object source) {        if (source == null)            throw new IllegalArgumentException("null source");        this.source = source;    }    /**     * The object on which the Event initially occurred.     *     * @return   The object on which the Event initially occurred.     */    public Object getSource() {        return source;    }    /**     * Returns a String representation of this EventObject.     *     * @return  A a String representation of this EventObject.     */    public String toString() {        return getClass().getName() + "[source=" + source + "]";    }

下面再看看，ContextLoader有什么幺蛾子。。。具体参见：http://blog.csdn.net/chenpeng19910926/article/details/71195202

解释上说的话：当ContextLoaderListener 被调用的时候当 root application context真正初始化的时候被调用

做了啥事情：

1. 查找web.xml中

  <context-param>        <param-name>contextClass</param-name>        <param-value>com.chenpeng.test</param-value>    </context-param>

来指定context class的类型：默认是

org.springframework.web.context.support.XmlWebApplicationContext

 所有指定的context class 都需要实现接口

ConfigurableWebApplicationContext

2.处理web.xml中的contextConfigLocation

    <context-param>        <param-name>contextConfigLocation</param-name>        <param-value>classpath*:spring4-context.xml</param-value>    </context-param>

看看上面ContextLoader在看看ContextLoaderListener的代码就清晰了很多

public class ContextLoaderListener extends ContextLoader implements ServletContextListener {public ContextLoaderListener() {}public ContextLoaderListener(WebApplicationContext context) {super(context);}//Initialize the root web application context.来自于ServletContextListener@Overridepublic void contextInitialized(ServletContextEvent event) {initWebApplicationContext(event.getServletContext());//ContextLoader}@Overridepublic void contextDestroyed(ServletContextEvent event) {closeWebApplicationContext(event.getServletContext());//ContextLoaderContextCleanupListener.cleanupAttributes(event.getServletContext());}}

initWebApplicationContext：

     -->createWebApplicationContext(servletContext)—>XmlWebApplicationContext

//设置WebApplicationContext的id，保存WebApplicationContext到servletcontext中

      -->configureAndRefreshWebApplicationContext—>customizeContext一般是空—>determineContextInitializerClasses一般是空

                                                                                     AbstractApplicationContext—>refresh开启了spring的大门

由上可以看出XmlWebApplicationContext-->AbstractApplicationContext—>refresh（）开启了spring的大门