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javaWEB总结(29):理解多个Filter代码的执行顺序

2017-03-11 17:50 316 查看

项目结构

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
<display-name>javaWeb_29</display-name>
<welcome-file-list>
<welcome-file>Num1.jsp</welcome-file>
</welcome-file-list>

<filter>
<filter-name>Num1Filter</filter-name>
<filter-class>com.dao.chu.Num1Filter</filter-class>
</filter>
<filter-mapping>
<filter-name>Num1Filter</filter-name>
<url-pattern>/Num2.jsp</url-pattern>
</filter-mapping>

<filter>
<filter-name>Num2Filter</filter-name>
<filter-class>com.dao.chu.Num2Filter</filter-class>
</filter>
<filter-mapping>
<filter-name>Num2Filter</filter-name>
<url-pattern>/Num2.jsp</url-pattern>
</filter-mapping>

</web-app>

Num1Filter.java

package com.dao.chu;

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 Num1Filter implements Filter {

public void destroy() {
}

public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {

System.out.println("1.before Num1Filter");
chain.doFilter(request, response);
System.out.println("2.after Num1Filter");
}

public void init(FilterConfig fConfig) throws ServletException {
}

}

Num2Filter.java

package com.dao.chu;

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;

/**
* Servlet Filter implementation class Num2Filter
*/
public class Num2Filter implements Filter {

public void destroy() {
}

public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {

System.out.println("3.before Num2Filter");
chain.doFilter(request, response);
System.out.println("4.after Num2Filter");
}

public void init(FilterConfig fConfig) throws ServletException {
}

}

Num1.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Num1.jsp</title>
</head>
<body>
<a href="<%=request.getContextPath() %>/Num2.jsp">To Num2.jsp</a>
</body>
</html>

Num2.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Num2.jsp</title>
</head>
<body>
<%
System.out.println("5.Num2.jsp");
%>
</body>
</html>

运行结果

由结果可知，Filter是先依次执行放行前的代码，然后到达jsp页面，最后再依次返回执行放行后的代码。

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标签： java web

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