Listener,Filter,Servlet执行顺序和生命周期

  • 作者: 凯哥Java
  • java web
  • 时间:2020-10-31 10:00
  • 925人已阅读
简介 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)加

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)

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。


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()......

f5384b9ce6e64572e72d25f64c009216.png

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()......

a7f629420d5d089f11a6785748ca37a8.png

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)。


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