MVC案例-----登录验证

结构图：

View视图层：

 1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <!DOCTYPE html>
 4 <html>
 5 <head>
 6 <meta charset="UTF-8">
 7 <title>登录</title>
 8 </head>
 9 <body>
10     <form action="../Login" method="post">
11         姓名：<input type="text" name="uname"><br>
12         密码：<input type="password" name="upwd">
13         <input type="submit" value="提交">
14     </form>
15 </body>
16 </html>

控制器，LoginServlet：

 1 package dao;
 2 import java.io.IOException;
 3 import javax.servlet.ServletException;
 4 import javax.servlet.annotation.WebServlet;
 5 import javax.servlet.http.HttpServlet;
 6 import javax.servlet.http.HttpServletRequest;
 7 import javax.servlet.http.HttpServletResponse;
 8 
 9 import LoginDao.Login;
10 import LoginDao.LoginDao;
11 
12 
13 @WebServlet("/Login" )
14 
15 //控制器层：接收view请求，并分发给模型层处理
16 public class LoginServlet extends HttpServlet {
17 
18     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
19         request.setCharacterEncoding("UTF-8");
20         //获取前端数据
21         String name = request.getParameter("uname");
22         String pwd =request.getParameter("upwd");
23         
24         Login login = new Login(name,pwd);
25         
26         int result = LoginDao.login(login);
27         if(result >0) {
28             response.sendRedirect("jsp/welcome.jsp");//登录成功
29         }else {
30             response.sendRedirect("jsp/login.jsp");//登录失败，可能是密码有误，也可能是服务器出错
31         }
32     
33     }
34     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
35 
36 
37         doGet(request, response);
38     }
39 
40 }

LoginServlet.java

Model层：

 1 package LoginDao;
 2 
 3     public class Login {
 4     private String uname;
 5     private String upwd;
 6     
 7     public Login(String uname, String upwd, int id) {    
 8         this.uname = uname;
 9         this.upwd = upwd;
10         this.id = id;
11     }
12     public Login(String uname, String upwd) {
13         this.uname = uname;
14         this.upwd = upwd;    
15     }
16     public Login() {
17     
18     }
19     private int id;
20     public int getId() {
21         return id;
22     }
23     public void setId(int id) {
24         this.id = id;
25     }
26     public String getUname() {
27         return uname;
28     }
29     public void setUname(String uname) {
30         this.uname = uname;
31     }
32     public String getUpwd() {
33         return upwd;
34     }
35     public void setUpwd(String upwd) {
36         this.upwd = upwd;
37     }
38 
39     
40     
41     
42 
43 
44 }

构造方法：

 1 package LoginDao;
 2 
 3     public class Login {
 4     private String uname;
 5     private String upwd;
 6     
 7     public Login(String uname, String upwd, int id) {    
 8         this.uname = uname;
 9         this.upwd = upwd;
10         this.id = id;
11     }
12     public Login(String uname, String upwd) {
13         this.uname = uname;
14         this.upwd = upwd;    
15     }
16     public Login() {
17     
18     }
19     private int id;
20     public int getId() {
21         return id;
22     }
23     public void setId(int id) {
24         this.id = id;
25     }
26     public String getUname() {
27         return uname;
28     }
29     public void setUname(String uname) {
30         this.uname = uname;
31     }
32     public String getUpwd() {
33         return upwd;
34     }
35     public void setUpwd(String upwd) {
36         this.upwd = upwd;
37     }
38 
39 }

遇到的问题：

索引超出范围：

问题位置：模糊查询：select count(*) from login where uname = ? and upwd = ?

原因：“=”与“？”之间有空格，去掉中间的空格即可