Jsp&Servlet 用户登录功能实现

学习峰哥Jsp教程自学笔记，峰哥Java学习路线：http://www.java1234.com/javaxuexiluxiantu.html  

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();
	
	@Override
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		this.doPost(request, response);
	}

	@Override
	protected 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。