Listener,Filter,Servlet执行顺序和生命周期

朴灿烈づ我的快乐病毒、 2022-05-18 11:09 217阅读 0赞

Listener,Filter和servlet都是配置在web.xml文件中。

# Listener、Filter、Servlet定义： #

## 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)**

package com.xy.web.listener;
    import javax.servlet.ServletRequestAttributeEvent;
    import javax.servlet.ServletRequestAttributeListener;
    import javax.servlet.ServletRequestEvent;
    import javax.servlet.ServletRequestListener;
    import javax.servlet.http.HttpSessionEvent;
    import javax.servlet.http.HttpSessionListener;
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
     
    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： ##

package com.xy.web.filter;
     
    import java.io.IOException;
     
    import javax.servlet.Filter;
    import javax.servlet.FilterChain;
    import javax.servlet.FilterConfig;
    import javax.servlet.ServletException;
    import javax.servlet.ServletRequest;
    import javax.servlet.ServletResponse;
     
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
     
    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： ##

package com.xy.web.servlet;
     
    import java.io.IOException;
     
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
     
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
     
    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： ##

<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>
    
    <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>
    
    <listener>
        <listener-class>com.xy.web.listener.TestListener</listener-class>
    </listener>

配置好以后启动项目。

# 加载顺序： #

## 日志： ##

查看启动日志如下：

信息: Initializing Coyote HTTP/1.1 on http-80

............

2016-1-14 0:47:04 org.apache.catalina.core.ApplicationContext log  
***信息: ContextListener: contextInitialized()  
2016-1-14 0:47:04 org.apache.catalina.core.ApplicationContext log  
信息: SessionListener: contextInitialized()***

...........

**2016-01-14 00:47:23,369  INFO TestFilter:28 - ..............execute TestFilter  init().............**.  
2016-1-14 0:47:23 org.apache.catalina.core.ApplicationContext log  
**信息: Initializing Spring FrameworkServlet 'spring'**

...........

2016-1-14 0:47:25 org.apache.catalina.startup.Catalina start  
信息: Server startup in 21565 ms

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## 结论： ##

**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。**

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# 生命周期： #

## 日志： ##

访问项目路径：http://localhost/MyWebProject/common/test.do，访问action两次，打断点后查看日志情况：

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()......

![20160114003405039][]

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()......

![20160114003909219][]

关闭项目，打印日志如下：

2016-1-14 0:40:15 org.apache.coyote.http11.Http11Protocol pause  
信息: Pausing Coyote HTTP/1.1 on http-80  
2016-1-14 0:40:16 org.apache.catalina.core.StandardService stop  
信息: Stopping service Catalina  
**2016-1-14 0:40:16 org.apache.catalina.core.ApplicationContext log  
信息: SessionListener: contextDestroyed()  
2016-1-14 0:40:16 org.apache.catalina.core.ApplicationContext log  
信息: ContextListener: contextDestroyed()**  
**2016-01-14 00:40:16,561  INFO TestServlet:30 - ...TestServlet init() destory..........**  
.......  
**2016-01-14 00:40:22,091  INFO TestFilter:19 - ..............execute TestFilter destroy()..............**

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## 结论： ##

从启动，结束和运行时候的日志看：

**Listener生命周期：一直从程序启动到程序停止运行。**

**ServletRequestListener：每次访问一个Request资源前，都会执行requestInitialized()方法，方法访问完毕，都会执行requestDestroyed()方法。**

**HttpSessionListener：每次调用request.getSession()，都会执行sessionCreated()方法，执行session.invalidate()方法，都会执行sessionDestroyed()方法。**

**ServletRequestAttributeListener：每次调用request.setAttribute()都会执行attributeAdded()方法，如果set的key在request里面存在，就会执行attributeReplacerd()方法，调用request.removeAttribute()方法，都会执行attributeRemoved()方法。**

**Filter生命周期：程序启动调用Filter的init()方法**(永远只调用一次,具体看启动日志)**，程序停止调用Filter的destroy()方法**(永远只调用一次，具体看关闭日志)**，doFilter()方法每次的访问请求如果符合拦截条件都会调用**(程序第一次运行，会在servlet调用init()方法以后调用，不管第几次，都在调用doGet(),doPost()方法之前)**。**

**Servlet生命周期：程序第一次访问，会调用servlet的init()方法初始化(只执行一次，具体看日志)，每次程序执行都会根据请求调用doGet()或者doPost()方法，程序停止调用destory()方法(具体看结束日志)。**

[https://blog.csdn.net/javawebxy/article/details/50514046][https_blog.csdn.net_javawebxy_article_details_50514046]

[20160114003405039]: /images/20220518/dc7914a4d3b04712b35c82725268588d.png
[20160114003909219]: /images/20220518/cb45d94cda98416c8146cd77c567e026.png
[https_blog.csdn.net_javawebxy_article_details_50514046]: https://blog.csdn.net/javawebxy/article/details/50514046