javaweb学习总结 Session案例——实现用户登录

假设有一个用户名为sa的用户，密码是123，输入用户名和密码后点击登录，跳转至indexServlet，点击退出后先到LogoutServlet后重定向到login.html

为实现上述需求，定义了一个html文件和三个servlet

（1）login.html：用于显示用户登录的界面

（2）uesr类：保存信息

（3）indexServlet：用于显示网站的首界面，如果用户没有登录，就会提示用户没有登录，否则显示用户已经登录的信息

（4）LoginServlet：用于显示登录成功的界面 

（5）LogoutServlet：用于完成用户注销功能

   用户名:

 密码：

 
 

package cn.edu.bdu.mc03;

public class User {
    private String username;
    private String password;
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
}
 

package cn.edu.bdu.mc03;

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

/**
 * Servlet implementation class IndexServlet
 */
@WebServlet("/IndexServlet")
public class IndexServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public IndexServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //处理乱码
        response.setContentType("text/html;charset=utf-8");
        
        HttpSession session=request.getSession();
        User user = (User)session.getAttribute("user");
        PrintWriter out = response.getWriter();
        if(user==null){
            out.print("您还没有登录！");
        }
        else{
            out.print("您已经登录，欢迎您"+user.getUsername());
            response.getWriter().print("退出");
        }
        
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}
 

 

package cn.edu.bdu.mc03;

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;

/**
 * Servlet implementation class LoginServlet
 */
@WebServlet("/LoginServlet")
public class LoginServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public LoginServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=utf-8");//设置编码方式
        //获取文本框的内容
        String username=request.getParameter("username");
        String password=request.getParameter("password");
        //通过request.getAttribute("user");获取user对象  
        //User user=(User)request.getAttribute("user");
        if("sa".equals(username)&&"123".equals(password)){
            //用session保存会话信息
            User user=new User();
            user.setUsername(username);
            user.setPassword(password);
            request.getSession().setAttribute("user", user);
            //重定向到indexServlet
            response.sendRedirect("/chapter006/IndexServlet");
        }
        else {
            response.getWriter().print("用户名或密码错误！");
        }
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}
 

package cn.edu.bdu.mc03;

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;

/**
 * Servlet implementation class LogoutServlet
 */
@WebServlet("/LogoutServlet")
public class LogoutServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public LogoutServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.getSession().removeAttribute("user");
        response.sendRedirect("/chapter006/login.html");
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}