Jsp&Servlet 用户登录功能实现

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简介：

登录功能的业务层（business layer）用servlet实现。

表现层（presentation layer）用Jsp实现。

1，数据库创建：

创建数据库为db_jsp，表为t_user(字段包含id,userName,password)

如下所示：

2，实体类创建（User实体类）：

package com.demo.model;public class User {private int id;private String userName;private String password;public User(String userName, String password) {super();this.userName = userName;this.password = password;}public User() {super();}public int getId() {return id;}public void setId(int id) {this.id = id;}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;}}

3，DBUtil封装：

package com.demo.util;import java.sql.Connection;import java.sql.DriverManager;public class DBUtil {private String dbUrl="jdbc:mysql://localhost:3306/db_book";private String userName = "root";private String password = "123456";private String jdbcName = "com.mysql.jdbc.Driver";/** * 获取数据库链接 * @return * @throws Exception */public Connection getCon() throws Exception{Class.forName(jdbcName);Connection connection = DriverManager.getConnection(dbUrl,userName,password);return connection;}/** * 关闭数据库连接 * @param connection * @throws Exception */public void closeCon(Connection connection) throws Exception{if (null != connection) {connection.close();}}public static void main(String[] args) {DBUtil dbUtil = new DBUtil();try {dbUtil.getCon();System.out.println("数据库连接成功");} catch (Exception e) {System.out.println("数据库连接异常");}}}

4，DAO层实现：

package com.demo.dao;import java.sql.Connection;import java.sql.PreparedStatement;import java.sql.ResultSet;import com.demo.model.User;public class UserDao {public User login(Connection con,User user) throws Exception{User resultUser = null;String sql = "select * from t_user where userName=? and password=?";PreparedStatement pstmt = con.prepareStatement(sql);pstmt.setString(1, user.getUserName());pstmt.setString(2, user.getPassword());ResultSet rs =  pstmt.executeQuery();if (rs.next()) {resultUser = new User();resultUser.setId(rs.getInt("id"));resultUser.setUserName(rs.getString("userName"));resultUser.setPassword(rs.getString("password"));}return resultUser;}}

4，Servlet实现：

package com.demo.web;import java.io.IOException;import java.io.PrintWriter;import java.sql.Connection;import javax.servlet.RequestDispatcher;import javax.servlet.ServletContext;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.demo.dao.UserDao;import com.demo.model.User;import com.demo.util.DBUtil;public class LoginServlet  extends HttpServlet{/** *  */private static final long serialVersionUID = 1L;private DBUtil dbUtil = new DBUtil();private UserDao userDao = new UserDao();@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {this.doPost(request, response);}@Overrideprotected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {String userName = request.getParameter("userName");String password = request.getParameter("password");Connection con=null;try {User user = new User(userName,password);con = dbUtil.getCon();User currentUser = userDao.login(con, user);if (null == currentUser) {request.setAttribute("error", "用户名或密码错误");request.setAttribute("userName", userName);request.setAttribute("password", password);RequestDispatcher dispatcher = request.getRequestDispatcher("login.jsp");dispatcher.forward(request, response);}else {HttpSession session = request.getSession();session.setAttribute("currentUser",currentUser);response.sendRedirect("main.jsp");}} catch (Exception e) {e.printStackTrace();} }}

servlet配置如下：

  <servlet>  <servlet-name>LoginServlet</servlet-name>  <servlet-class>com.demo.web.LoginServlet</servlet-class>  </servlet>    <servlet-mapping>  <servlet-name>LoginServlet</servlet-name>  <url-pattern>/login</url-pattern>  </servlet-mapping>

5，登录的Jsp页面：

<%@ 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>登录页面</title></head><body><form action="login" method="post"><table><tr><th colspan="2">用户登录</th></tr><tr><td>用户名：</td><td><input type="text" id="userName" name="userName" value="${userName} "/></td></tr><tr><td>密码</td><td><input type="password" id="password" name="password" value="${password}"/></td></tr><tr><td><input type="submit"/></td><td><font color="red">${ error }</font></td></tr></table></form></body></html>

6，主页的Jsp页面：

<%@ 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>主页</title></head><body>当前登录用户：${currentUser.userName }</body></html>

业务实现过程：

访问login.jsp，将信息表单提交到loginservlet进行业务逻辑的处理，根据是否查到相关的用户。

查到用户，客户端跳转至主页，显示用户的相关信息。

未查到用户，服务器重定向至login.jsp并附带错误信息。

效果图如下：

错误情况下：

正确情况下：

至此，功能实现。