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IT兄弟连 JavaWeb教程经典案例

案例需求：编写一个jsp servlet程序,在login.jsp发起login.do登录请求，当输入的用户名是abc密码是123时，则判断是登录成功，其它暂时认为是登录失败。当用户登录成功时，将用户名放入session对象中并跳转到main.jsp。当用户登录失败时向request对象中存放一个msg消息，内容是登录失败。再发送一个orderInfo.do的查看订单信息的请求，可以跳转到orderInfo.jsp。在上面程序的基础上,写一个过滤器，要求用户登录成功才能查看订单信息。

案例实现：

● 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>

<title>Insert title here</title>

</head>

<body>

<form action="login.do">

      用户名:<input  type="text"   name="username" > <br>

      密码: <input  type="password"   name="userpassword" > <br>

 <input  type="submit"  value="登录">  <span>${msg}</span>

 </form>

</body>

</html>

● main.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>

<title>Insert title here</title>

</head>

<body>

<h1> 欢迎  ${username} </h1>

</body>

</html>

● orderInfo.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>

<title>Insert title here</title>

</head>

<body>

<h1> 查看订单信息中....  </h1>

</body>

</html>

● XdlUserLoginController.java :

package com.xdl.controller;

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.annotation.WebServlet;

@WebServlet("/login.do")

public class XdlUserLoginController extends HttpServlet {

@Override

protected void service(HttpServletRequest request,

    HttpServletResponse response) throws ServletException, IOException {

     // 获取页面请求参数

    String  username = request.getParameter("username");

    String  userpassword = request.getParameter("userpassword");

    System.out.println("登录中...");

    if("abc".equals(username) && "123".equals(userpassword)){

         request.getSession().setAttribute("username", username);

         response.sendRedirect("main.jsp");

    }else{

         request.setAttribute("msg", "登录失败");

         request.getRequestDispatcher("login.jsp").

             forward(request, response);

    }

}

}

● XdlOrderInfoController.java:

package com.xdl.controller;

import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

@WebServlet("/orderInfo.do")

public class XdlOrderInfoController extends HttpServlet {

private static final long serialVersionUID = 1L;

protected void service(HttpServletRequest request,

    HttpServletResponse response) throws ServletException, IOException {

    request.getRequestDispatcher("orderInfo.jsp").

            forward(request, response);

}

}

● 检查登录的过滤器:

package com.xdl.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;

@WebFilter("*.do")

public class XdlCheckLoginFilter implements Filter {

@Override

public void destroy() {

}

@Override

public void doFilter(ServletRequest arg0, ServletResponse arg1,

         FilterChain chain)

         throws IOException, ServletException {

    // 放行 如果用户已经登录了  则放行  如果没登录则跳转到 登录页面

    // 注意 登录请求时不能拦截的  是否登录参考的是 session 有没有 username

    HttpServletRequest request = (HttpServletRequest)arg0;

    HttpServletResponse response = (HttpServletResponse)arg1;

    String servletPath = request.getServletPath();

    if("/login.do".equals(servletPath)){

         chain.doFilter(arg0, arg1);

    }else{

         /* System.out.println("此路是我开 此树是我栽  要想从此过 留下李伟杰");

         chain.doFilter(arg0, arg1);

          System.out.println("你回来了? 怎么又是你  你走吧"); */

         String username = (String)

                request.getSession().getAttribute ("username");

        if(username == null){

           // 跳转到登录页面

             response.sendRedirect("login.jsp");

        }else{

           chain.doFilter(arg0, arg1);

        }

    }

}

}

原文 https://blog.51cto.com/14311187/2404042

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