小峰servlet/jsp（3）登陆功能实现

一、User模型：

User.java:

 1 package com.java1234.model;
 2 
 3 public class User {
 4 
 5     private int id;
 6     private String userName;
 7     private String password;
 8     
 9     
10     
11     public User() {
12         super();
13         // TODO Auto-generated constructor stub
14     }
15     
16     
17     public User(String userName, String password) {
18         super();
19         this.userName = userName;
20         this.password = password;
21     }
22 
23 
24     public int getId() {
25         return id;
26     }
27     public void setId(int id) {
28         this.id = id;
29     }
30     public String getUserName() {
31         return userName;
32     }
33     public void setUserName(String userName) {
34         this.userName = userName;
35     }
36     public String getPassword() {
37         return password;
38     }
39     public void setPassword(String password) {
40         this.password = password;
41     }
42     
43     
44 }
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 二、封装jdbc连接数据库：

 1 package com.java1234.util;
 2 
 3 import java.sql.Connection;
 4 import java.sql.DriverManager;
 5 
 6 public class DbUtil {
 7 
 8     private String dbUrl="jdbc:mysql://localhost:3306/db_jsp";
 9     private String dbUserName="root";
10     private String dbPassword="123456";
11     private String jdbcName="com.mysql.jdbc.Driver";
12     
13     public Connection getCon()throws Exception{
14         Class.forName(jdbcName);
15         Connection con=DriverManager.getConnection(dbUrl, dbUserName, dbPassword);
16         return con;
17     }
18     
19     public void closeCon(Connection con)throws Exception{
20         if(con!=null){
21             con.close();
22         }
23     }
24     
25     public static void main(String[] args) {
26         DbUtil dbUtil=new DbUtil();
27         try {
28             dbUtil.getCon();
29             System.out.println("连接成功");
30         } catch (Exception e) {
31             e.printStackTrace();
32         }
33     }
34 }
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三、userDao：

 1 package com.java1234.dao;
 2 
 3 import java.sql.Connection;
 4 import java.sql.PreparedStatement;
 5 import java.sql.ResultSet;
 6 
 7 import com.java1234.model.User;
 8 
 9 public class UserDao {
10 
11     public User login(Connection con,User user)throws Exception{
12         User resultUser=null;
13         String sql="select * from t_user where userName=? and password=?";
14         PreparedStatement pstmt=con.prepareStatement(sql);
15         pstmt.setString(1, user.getUserName());
16         pstmt.setString(2, user.getPassword());
17         ResultSet rs=pstmt.executeQuery();
18         if(rs.next()){
19             resultUser=new User();
20             resultUser.setUserName(rs.getString("userName"));
21             resultUser.setPassword(rs.getString("password"));
22         }
23         return resultUser;
24     }
25             
26 }
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 四、loginServlet.java:

 1 package com.java1234.web;
 2 
 3 import java.io.IOException;
 4 import java.sql.Connection;
 5 
 6 import javax.servlet.ServletException;
 7 import javax.servlet.http.HttpServlet;
 8 import javax.servlet.http.HttpServletRequest;
 9 import javax.servlet.http.HttpServletResponse;
10 import javax.servlet.http.HttpSession;
11 
12 import com.java1234.dao.UserDao;
13 import com.java1234.model.User;
14 import com.java1234.util.DbUtil;
15 
16 public class LoginServlet extends HttpServlet{
17 
18     /**
19      * 
20      */
21     private static final long serialVersionUID = 1L;
22     
23     DbUtil dbUtil=new DbUtil();
24     UserDao userDao=new UserDao();
25 
26     @Override
27     protected void doGet(HttpServletRequest request, HttpServletResponse response)
28             throws ServletException, IOException {
29         this.doPost(request, response);
30     }
31 
32     @Override
33     protected void doPost(HttpServletRequest request, HttpServletResponse response)
34             throws ServletException, IOException {
35         String userName=request.getParameter("userName");
36         String password=request.getParameter("password");
37         
38         Connection con=null;
39         try {
40             User user=new User(userName,password);
41             con=dbUtil.getCon();
42             User currentUser=userDao.login(con, user);
43             if(currentUser==null){
44                 request.setAttribute("error", "用户名或密码错误");
45                 request.setAttribute("userName", userName);
46                 request.setAttribute("password", password);
47                 request.getRequestDispatcher("login.jsp").forward(request, response);
48             }else{
49                 HttpSession session=request.getSession();
50                 session.setAttribute("currentUser", currentUser);
51                 response.sendRedirect("main.jsp");
52             }
53         } catch (Exception e) {
54             e.printStackTrace();
55         }
56     }
57     
58     
59 }
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前台登陆界面login.jsp:

 1 <%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
 2 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 3 <html>
 4 <head>
 5 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 6 <title>Insert title here</title>
 7 </head>
 8 <body>
 9 <form action="login" method="post">
10 <table>
11     <tr>
12         <th colspan="2">用户登录</th>
13     </tr>
14     <tr>
15         <td>用户名：</td>
16         <td><input type="text" id="userName" name="userName" value="${userName }"/></td>
17     </tr>
18     <tr>
19         <td>密码：</td>
20         <td><input type="password" id="password" name="password" value="${password }"/></td>
21     </tr>
22     <tr>
23         <td><input type="submit" value="登录"/></td>
24         <td><font color="red">${error }</font></td>
25     </tr>
26 </table>
27 </form>
28 </body>
29 </html>
View Code

登陆成功后跳转到main.jsp：

 1 <%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
 2 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 3 <html>
 4 <head>
 5 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 6 <title>Insert title here</title>
 7 </head>
 8 <body>
 9 主页！当前登录用户：${currentUser.userName } &nbsp;&nbsp;<a href="logout">注销</a>
10 </body>
11 </html>
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五、注销方法：

LogoutServlet.java:

 1 package com.java1234.web;
 2 
 3 import javax.servlet.ServletException;
 4 import javax.servlet.http.HttpServlet;
 5 import javax.servlet.http.HttpServletRequest;
 6 import javax.servlet.http.HttpServletResponse;
 7 
 8 
 9 public class LogoutServlet extends HttpServlet{
10     /**
11      * 
12      */
13     private static final long serialVersionUID = 1L;
14 
15     @Override
16     protected void doGet(HttpServletRequest request, HttpServletResponse response)
17             throws ServletException, IOException {
18         this.doPost(request, response);
19     }
20 
21     @Override
22     protected void doPost(HttpServletRequest request, HttpServletResponse response)
23             throws ServletException, IOException {
24         request.getSession().invalidate();
25         response.sendRedirect("login.jsp");
26     }
27     
28     
29 }
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六、loginServlet.java/LogoutServlet.java两个servlet在web.xml中的配置：

web.xml配置：

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <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">
 3   <display-name>HeadFirstJspServletChap05</display-name>
 4   <welcome-file-list>
 5     <welcome-file>index.html</welcome-file>
 6     <welcome-file>index.htm</welcome-file>
 7     <welcome-file>index.jsp</welcome-file>
 8     <welcome-file>default.html</welcome-file>
 9     <welcome-file>default.htm</welcome-file>
10     <welcome-file>default.jsp</welcome-file>
11   </welcome-file-list>
12 
13   <servlet>
14       <servlet-name>loginServlet</servlet-name>
15       <servlet-class>com.java1234.web.LoginServlet</servlet-class>
16   </servlet>
17   
18   <servlet-mapping>
19       <servlet-name>loginServlet</servlet-name>
20       <url-pattern>/login</url-pattern>
21   </servlet-mapping>
22   
23   <servlet>
24       <servlet-name>logoutServlet</servlet-name>
25       <servlet-class>com.java1234.web.LogoutServlet</servlet-class>
26   </servlet>
27   
28   <servlet-mapping>
29       <servlet-name>logoutServlet</servlet-name>
30       <url-pattern>/logout</url-pattern>
31   </servlet-mapping>
32   
33   <filter>
34       <filter-name>loginFilter</filter-name>
35       <filter-class>com.java1234.filter.LoginFilter</filter-class>
36   </filter>
37   
38   <filter-mapping>
39       <filter-name>loginFilter</filter-name>
40       <url-pattern>/*</url-pattern>
41   </filter-mapping>
42   
43   <listener>
44       <listener-class>
45           com.java1234.listener.SessionAttributeListener
46       </listener-class>
47   </listener>
48 </web-app>
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七、Servlet过滤器：

过滤用户请求；

添加登陆过滤器，LoignFilter.java:

 1 package com.java1234.filter;
 2 
 3 import java.io.IOException;
 4 
 5 import javax.servlet.Filter;
 6 import javax.servlet.FilterChain;
 7 import javax.servlet.FilterConfig;
 8 import javax.servlet.ServletException;
 9 import javax.servlet.ServletRequest;
10 import javax.servlet.ServletResponse;
11 import javax.servlet.http.HttpServletRequest;
12 import javax.servlet.http.HttpSession;
13 
14 public class LoginFilter implements Filter{
15 
16     public void destroy() {
17         
18     }
19 
20     public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse,
21             FilterChain filterChain) throws IOException, ServletException {
22         HttpServletRequest request=(HttpServletRequest)servletRequest;
23         HttpSession session=request.getSession();
24         Object o=session.getAttribute("currentUser");
25         String path=request.getServletPath();        //获取用户请求的路径 "/login"
26         if(o==null&&path.indexOf("login")<0){
27             request.getRequestDispatcher("login.jsp").forward(servletRequest, servletResponse);
28         }else{
29             filterChain.doFilter(servletRequest, servletResponse);
30         }
31     }
32 
33     public void init(FilterConfig arg0) throws ServletException {
34         
35     }
36 
37 }
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 八、Servlet监听器：

监听web事件，如application、session、request

 1 package com.java1234.listener;
 2 
 3 import javax.servlet.http.HttpSessionAttributeListener;
 4 import javax.servlet.http.HttpSessionBindingEvent;
 5 
 6 public class SessionAttributeListener implements HttpSessionAttributeListener{
 7 
 8     //session中添加attribute时候会监听到
 9     public void attributeAdded(HttpSessionBindingEvent httpSessionBindingEvent) {
10         System.out.println("添加的属性名: "+httpSessionBindingEvent.getName()+",属性值："+httpSessionBindingEvent.getValue());
11     }
12 
13     public void attributeRemoved(HttpSessionBindingEvent httpSessionBindingEvent) {
14         System.out.println("删除的属性名: "+httpSessionBindingEvent.getName()+",属性值："+httpSessionBindingEvent.getValue());
15     }
16 
17     public void attributeReplaced(HttpSessionBindingEvent httpSessionBindingEvent) {
18         
19     }
20 
21 }
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配置listener见上面的web.xml;

登陆成功后，就能看到console打印：

servlet中跳转的两种方式：

response.sendRedirect("target.jsp");      　　　　//客户端跳转/重定向

request.getRequestDispatcher("target.jsp").forward(request, response);    //服务器端跳转/转发

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原文地址：https://www.cnblogs.com/tenWood/p/6505291.html