servlet串行拦截器实现例子

至于串行过滤器有什么作用，我实在不知。我的理解是它只是说明 过滤器的串行运行方式

需求：当用户没有登录访问更新页面的时候，跳转到登录页面

1.登录页面：login.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>Insert title here</title>
</head>
<body>
<form action="UserLoginServlet" method="post">
    username:<input type="text" value="<%=null == request.getAttribute("username")?"" : request.getAttribute("username") %>" name="username"><br>
    password:<input type="text" name="password"><br>
    
    authority:<select  name="authority">
    
        <option value="1" <%="1".equals(request.getAttribute("authority"))?"selected = selected" : "" %>>common user</option>
        <option value="2" <%="2".equals(request.getAttribute("authority"))?"selected = selected" : "" %>>adminstrator</option>
    </select>
    <br>
    <input type="submit">
</form>

</body>
</html>
login.jsp

2.登录页面的servet容器

package com.filter;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import com.javabean.User;

public class UserLoginServlet extends HttpServlet
{
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException
    {

        String username = (String)req.getParameter("username");
        String password = (String)req.getParameter("password");
        String authority = (String)req.getParameter("authority");
        
        if("1".equals(authority) && "zhangsan".equals(username) && "123".equals(password))
        {
            User user = new User();
            user.setUsername(username);
            user.setPassword(password);
            user.setAuthority(authority);
            
            HttpSession session = req.getSession();
            
            session.setAttribute("user",user);
            
            req.getRequestDispatcher("index.jsp").forward(req, resp);
            
            return ;
        }
        if("2".equals(authority) && "lisi".equals(username) && "456".equals(password))
        {
            User user = new User();
            user.setUsername(username);
            user.setPassword(password);
            user.setAuthority(authority);
            
            HttpSession session = req.getSession();
            
            session.setAttribute("user",user);
            
            req.getRequestDispatcher("index.jsp").forward(req, resp);
            
            return ;
        }
        
        System.out.println("meiyou denglu");
        
        resp.sendRedirect("login.jsp?error=true&username="+username+"&authority="+authority);
        
    }
    
}
UserLoginServlet

3.主页面index.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
    <%@ page import="com.javabean.User" %>
<!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>Insert title here</title>
</head>
<body>
<a href="QueryServletFilter">query</a><br>
<% 
User user = (User)session.getAttribute("user");
if(null == user)
{
    response.sendRedirect("login.jsp");
    return;
}
    if("2".equals(((User)session.getAttribute("user")).getAuthority())){
            
%>
<a href="UpdateServletFilter">update</a>

<%} %>
</body>
</html>
index.jsp

4.查询servlet. QueryServletFilter

package com.filter;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class QueryServletFilter extends HttpServlet
{
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException
    {
        System.out.println("QueryServletFilter run");
    }
}
View Code

5.更新servlet容器. UpdateServletFilter

package com.filter;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class UpdateServletFilter extends HttpServlet
{
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException
    {
        System.out.println("UpdateServletFilter run");
    }
}
UpdateServletFilter

6.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_2_5.xsd" id="WebApp_ID" version="2.5">
  <display-name>filter</display-name>
  
 <servlet>
     <servlet-name>UserLoginServlet</servlet-name>
     <servlet-class>com.filter.UserLoginServlet</servlet-class>
 </servlet>
 
 
  <servlet-mapping>
     <servlet-name>UserLoginServlet</servlet-name>
     <url-pattern>/filter/UserLoginServlet</url-pattern>
 </servlet-mapping>

 
 <servlet>
     <servlet-name>QueryServletFilter</servlet-name>
     <servlet-class>com.filter.QueryServletFilter</servlet-class>
 </servlet>
 
 <servlet-mapping>
     <servlet-name>QueryServletFilter</servlet-name>
     <url-pattern>/filter/QueryServletFilter</url-pattern>
 </servlet-mapping>
 
 <servlet>
     <servlet-name>UpdateServletFilter</servlet-name>
     <servlet-class>com.filter.UpdateServletFilter</servlet-class>
 </servlet>
 
 <servlet-mapping>
     <servlet-name>UpdateServletFilter</servlet-name>
     <url-pattern>/filter/UpdateServletFilter</url-pattern>
 </servlet-mapping>
  <!-- filter start -->
  <filter>
      <description>this is the servlet filter example</description>
      <filter-name>userLoginServletFilter1</filter-name>
      <filter-class>com.filter.UserLoginServletFilter</filter-class>
  </filter>
  
    <!-- 演示过滤器串行运行 -->
  <filter>
      <description>this is the servlet filter example</description>
      <filter-name>userLoginServletFilter2</filter-name>
      <filter-class>com.filter.UserLoginServletFilter2</filter-class>
  </filter>
  
  <!-- url-pattern表示只过滤 UpdateServletFilter这一个servlet容器-->
  <filter-mapping>
      <filter-name>userLoginServletFilter1</filter-name>
      <url-pattern>/filter/UpdateServletFilter</url-pattern>
  </filter-mapping>
  

  <!-- url-pattern表示只过滤 UpdateServletFilter这一个servlet容器-->
  <filter-mapping>
      <filter-name>userLoginServletFilter2</filter-name>
      <url-pattern>/filter/UpdateServletFilter</url-pattern>
  </filter-mapping>
  
  <!-- filter end -->
</web-app>
web.xml

 7.filter拦截器 UserLoginServletFilter

package com.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 javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;


public class UserLoginServletFilter implements Filter
{

    @Override
    public void destroy()
    {
      System.out.println("destroy");
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain filterChain) throws IOException, ServletException
    {

        HttpServletRequest req = (HttpServletRequest)request;
        HttpSession s = req.getSession();
        
        if(req.getRequestURI().endsWith("login.jsp") || req.getRequestURI().endsWith("UserLoginServlet"))
        {
            System.out.println("Filter1 start");
            filterChain.doFilter(request, response);
            System.out.println("filter1 end");
            return ;
        }
        
        if(null ==  s.getAttribute("user"))
        {
            System.out.println("Filter1 start..");
            ((HttpServletResponse)response).sendRedirect("login.jsp");
            return;
        }
        else
        {
            System.out.println("Filter1 start....");
            filterChain.doFilter(request, response);
           
        }
        
    }

    @Override
    public void init(FilterConfig filterConfig) throws ServletException
    {
       System.out.println("init");
    }
    
}
UserLoginServletFilter

8.filter拦截器2 UserLoginServletFilter2

package com.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;

public class UserLoginServletFilter2 implements Filter
{

    @Override
    public void destroy()
    {
       System.out.println("destory2");
        
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain filterChain) throws IOException, ServletException
    {
       System.out.println("doFilter2 start");
       filterChain.doFilter(request, response);
       System.out.println("doFilter2 end");
        
    }

    @Override
    public void init(FilterConfig arg0) throws ServletException
    {
        System.out.println("init2");
    }
    
}
UserLoginServletFilter2

web.xml中url-pattern属性值表示访问的路径。

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原文地址：https://www.cnblogs.com/feiguo/p/3804019.html