淺談Listener、Filter、Servlet初始化順序

Listener、Filter、Servlet都有一個初始化的過程，對應的方法分別為：

contextInitialized(ServletContextEvent arg0)

init(FilterConfig filterConfig)

init(ServletConfig config)

那麼它們的初始化順序是什麼呢?

Listener > Filter > Servlet

TestServlet.Java

Java代碼

package com.cos;     
import Java.io.IOException;     
import Javax.servlet.GenericServlet;     
import Javax.servlet.ServletConfig;     
import Javax.servlet.ServletException;     
import Javax.servlet.ServletRequest;     
import Javax.servlet.ServletResponse;     
    
public class TestServlet extends GenericServlet {     
    @Override    
    public void init(ServletConfig config){     
        System.out.println("Servlet 初始化 。。。");     
    }     
    @Override    
    public void service(ServletRequest arg0, ServletResponse arg1) throws ServletException, IOException {     
        System.out.println("Servlet service 。。。");     
    }     
}    

TestFilter.Java

Java代碼

package com.cos;     
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;     
    
public class TestFilter implements Filter{     
    public void init(FilterConfig filterConfig) throws ServletException {     
        System.out.println("Filter 初始化。。。");     
    }     
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {     
        System.out.println("doFilter 。。。");     
        chain.doFilter(request, response);     
    }     
    public void destroy() {     
        System.out.println("Filter 銷毀。。。");     
    }     
}   

TestListener.Java

Java代碼

package com.cos;     
import Javax.servlet.ServletContextEvent;     
import Javax.servlet.ServletContextListener;     
    
public class TestListener implements ServletContextListener{     
    public void contextInitialized(ServletContextEvent arg0) {     
        System.out.println("Listener 初始化。。。");     
    }     
    public void contextDestroyed(ServletContextEvent arg0) {     
        System.out.println("Listener 銷毀。。。");     
    }     
}  

web.XML

XML代碼

<web-app version="2.5" XMLns="http://java.sun.com/XML/ns/Javaee" XMLns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/XML/ns/Javaee/web-app_2_5.xsd">    
    <servlet>    
        <servlet-name>sservlet-name>    
        <servlet-class>com.cos.TestServletservlet-class>    
    servlet>    
    <servlet-mapping>    
        <servlet-name>sservlet-name>    
        <url-pattern>/loginurl-pattern>    
    servlet-mapping>    
    <filter>    
        <filter-name>ffilter-name>    
        <filter-class>com.cos.TestFilterfilter-class>    
    filter>    
    <filter-mapping>    
        <filter-name>ffilter-name>    
        <url-pattern>/*url-pattern>    
    filter-mapping>    
    <listener>    
        <listener-class>com.cos.TestListenerlistener-class>    
    listener>    
web-app>