Listener、Filter、Servlet执行顺序

结构图

Listener:

首先定义一个Listener，实现以下接口：
HttpSessionListener(用来监控session的创建，销毁等)
ServletRequestListener(用于监控servlet上下文request)
ServletRequestAttributeListener(用于监控request中的attribute的操作)

public class TestListener implements HttpSessionListener,ServletRequestListener,ServletRequestAttributeListener {  
    private Logger logger = LoggerFactory.getLogger(TestListener.class);  
      
    //sessionListener start!  
    public void sessionCreated(HttpSessionEvent arg0) {  
        logger.info(".......TestListener sessionCreated().......");  
    }  
  
    public void sessionDestroyed(HttpSessionEvent arg0) {  
        logger.info(".......TestListener sessionDestroyed().......");  
    }  
    //sessionListener end!  
      
    //requestListener start!  
    public void requestInitialized(ServletRequestEvent arg0) {  
        logger.info("......TestListener requestInitialized()......");  
    }  
  
    public void requestDestroyed(ServletRequestEvent arg0) {  
        logger.info("......TestListener requestDestroyed()......");  
    }  
    //requestListener end!  
      
    //attributeListener start!  
    public void attributeAdded(ServletRequestAttributeEvent srae) {  
        logger.info("......TestListener attributeAdded()......");  
    }  
  
    public void attributeRemoved(ServletRequestAttributeEvent srae) {  
        logger.info("......TestListener attributeRemoved()......");  
    }  
  
    public void attributeReplaced(ServletRequestAttributeEvent srae) {  
        logger.info("......TestListener attributeReplaced()......");  
    }  
    //attributeListener end!  
} 

Filter：

public class TestFilter implements Filter {  
    private Logger logger = LoggerFactory.getLogger(TestFilter.class);  
  
    public void destroy() {  
        logger.info("..............execute TestFilter destory()..............");  
    }  
  
    public void doFilter(ServletRequest arg0, ServletResponse arg1,FilterChain arg2) throws IOException, ServletException {  
        logger.info("..............execute TestFilter doFilter()..............");  
        arg2.doFilter(arg0, arg1);  
    }  
  
    public void init(FilterConfig arg0) throws ServletException {  
        logger.info("..............execute TestFilter  init()..............");  
    }  
}  

Servlet

public class TestServlet extends HttpServlet {  
  
    private Logger logger = LoggerFactory.getLogger(TestServlet.class);  
  
    /** 
     *  
     */  
    private static final long serialVersionUID = -4263672728918819141L;  
  
    @Override  
    public void init() throws ServletException {  
        logger.info("...TestServlet init() init..........");  
        super.init();  
    }  
      
    @Override  
    public void destroy() {  
        logger.info("...TestServlet init() destory..........");  
        super.destroy();  
    }  
    @Override  
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)  
            throws ServletException, IOException {  
        this.doPost(req, resp);  
    }  
      
    @Override  
    protected void doPost(HttpServletRequest request, HttpServletResponse response)  
            throws ServletException, IOException {  
        logger.info("...TestServlet doPost() start..........");  
        //操作attribute  
        request.setAttribute("a", "a");  
        request.setAttribute("a", "b");  
        request.getAttribute("a");  
        request.removeAttribute("a");  
        //操作session  
        request.getSession().setAttribute("a", "a");  
        request.getSession().getAttribute("a");  
        request.getSession().invalidate();  
        logger.info("...TestServlet doPost() end..........");  
    }  
}  

配置XML

<!-- 测试filter -->  
<filter>  
    <filter-name>TestFilter</filter-name>  
    <filter-class>com.xy.web.filter.TestFilter</filter-class>  
</filter>  
<filter-mapping>  
    <filter-name>TestFilter</filter-name>  
    <url-pattern>*.do</url-pattern>  
</filter-mapping>  
<!-- 测试servlet -->  
<servlet>  
    <servlet-name>TestServlet</servlet-name>  
    <servlet-class>com.xy.web.servlet.TestServlet</servlet-class>  
</servlet>  
<servlet-mapping>  
    <servlet-name>TestServlet</servlet-name>  
    <url-pattern>/*</url-pattern>  
</servlet-mapping>  
<!-- 测试listener -->  
<listener>  
    <listener-class>com.xy.web.listener.TestListener</listener-class>  
</listener>  

配置好以后启动项目。

加载顺序

从启动日志来看，
启动的顺序为listener->Filter->servlet.
简单记为：理(Listener)发(Filter)师(servlet).
执行的顺序不会因为三个标签在配置文件中的先后顺序而改变。

生命周期

第一次访问：
2016-01-14 00:03:03,991 INFO TestListener:26 - ......TestListener requestInitialized()......
2016-01-14 00:03:04,001 INFO TestServlet:24 - ...TestServlet init() init..........
2016-01-14 00:03:04,011 INFO TestFilter:23 - ..............execute TestFilter doFilter()..............
2016-01-14 00:03:15,275 INFO TestServlet:42 - ...TestServlet doPost() start..........
2016-01-14 00:03:16,255 INFO TestListener:36 - ......TestListener attributeAdded()......
2016-01-14 00:03:16,853 INFO TestListener:44 - ......TestListener attributeReplaced()......
2016-01-14 00:03:18,561 INFO TestListener:40 - ......TestListener attributeRemoved()......
2016-01-14 00:03:20,065 INFO TestListener:16 - .......TestListener sessionCreated().......
2016-01-14 00:03:22,908 INFO TestListener:20 - .......TestListener sessionDestroyed().......
2016-01-14 00:03:25,624 INFO TestServlet:52 - ...TestServlet doPost() end..........
2016-01-14 00:03:27,746 INFO TestListener:30 - ......TestListener requestDestroyed()......

第二次访问：
2016-01-14 00:04:08,908 INFO TestListener:26 - ......TestListener requestInitialized()......
2016-01-14 00:04:08,909 INFO TestFilter:23 - ..............execute TestFilter doFilter()..............
2016-01-14 00:04:14,385 INFO TestServlet:42 - ...TestServlet doPost() start..........
2016-01-14 00:04:14,778 INFO TestListener:36 - ......TestListener attributeAdded()......
2016-01-14 00:04:14,974 INFO TestListener:44 - ......TestListener attributeReplaced()......
2016-01-14 00:04:15,342 INFO TestListener:40 - ......TestListener attributeRemoved()......
2016-01-14 00:04:15,904 INFO TestListener:16 - .......TestListener sessionCreated().......
2016-01-14 00:04:17,354 INFO TestListener:20 - .......TestListener sessionDestroyed().......
2016-01-14 00:04:17,815 INFO TestServlet:52 - ...TestServlet doPost() end..........
2016-01-14 00:04:19,044 INFO TestListener:30 - ......TestListener requestDestroyed()......