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>

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");

    }

}

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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