JAVA 用于练手的超简单登录注册，jdbc实现【学习笔记】

简单的不能再简单的登录注册，页面简陋，原理在就好！

需要用到的表：

字段其实用不了这么多，为了方便我就这么弄了。

然后jsp页面：

login.jsp

success.jsp

就一句登录成功就OK。

fail.jsp

register.jsp

接下来：

第一步：将字段取出并封装，我们称之为实体类。

package com.tf.entity;public class User {private int userId;private String username;private int sex;private String password;private int flag;public int getUserId() {return userId;}public void setUserId(int userId) {this.userId = userId;}public String getUsername() {return username;}public void setUsername(String username) {this.username = username;}public int getSex() {return sex;}public void setSex(int sex) {this.sex = sex;}public String getPassword() {return password;}public void setPassword(String password) {this.password = password;}public int getFlag() {return flag;}public void setFlag(int flag) {this.flag = flag;}}

第二步：写dao里面操作数据的方法，顺手将工具类放进util包里。

package com.tf.dao;import java.sql.Connection;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;import com.tf.entity.User;import com.tf.util.DBConnectionUtil;public class UserDao {Connection conn=null;PreparedStatement ps=null;ResultSet rs=null;//通过username查询用户（注册前查询是否已有这个username）public User getUserByUsername(String username){User user =null;try {conn=DBConnectionUtil.getConnection();String sql="select * from user where username=?";ps=conn.prepareStatement(sql);System.out.println(sql);ps.setString(1, username);rs=ps.executeQuery();if(rs.next()){user=new User();user.setUserId(rs.getInt("userId"));user.setUsername(rs.getString(2));user.setPassword(rs.getString(3));user.setSex(rs.getInt(4));user.setFlag(rs.getInt(5));}} catch (SQLException e) {e.printStackTrace();}finally{DBConnectionUtil.closeAll(ps, conn, rs);}return user;}//通过username与password查询用户（查询到即可登录）public User getUserByUsernameAndPassword(String username,String password){User user =null;try {conn=DBConnectionUtil.getConnection();String sql="select * from user where username=? and password=?";ps=conn.prepareStatement(sql);System.out.println(sql);ps.setString(1, username);ps.setString(2, password);rs=ps.executeQuery();if(rs.next()){user=new User();user.setUserId(rs.getInt("userId"));user.setUsername(rs.getString(2));user.setPassword(rs.getString(3));user.setSex(rs.getInt(4));user.setFlag(rs.getInt(5));}} catch (SQLException e) {e.printStackTrace();}finally{DBConnectionUtil.closeAll(ps, conn, rs);}return user;}//增加（注册进去）public boolean saveUser(User user){boolean flag=false;try {conn=DBConnectionUtil.getConnection();String sql="insert into user(username,password) values(?,?)";ps=conn.prepareStatement(sql);System.out.println(sql);ps.setString(1, user.getUsername());ps.setString(2, user.getPassword());int rows=ps.executeUpdate();if(rows>0)flag=true;} catch (SQLException e) {e.printStackTrace();}finally{DBConnectionUtil.closeAll(ps, conn, rs);}return flag;}}

第三步：写处理业务逻辑的service。

package com.tf.service;import com.tf.dao.UserDao;import com.tf.entity.User;public class UserService {private UserDao userDao=new UserDao();public User getUserByUsernameAndPassword(String username,String password){return userDao.getUserByUsernameAndPassword(username, password);}public boolean saveUser(User user){return userDao.saveUser(user);}public User getUserByUsername(String username){return userDao.getUserByUsername(username);}}

第四步：写servlet。

登录：

package com.tf.web.servlet;import java.io.IOException;import java.io.PrintWriter;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.tf.entity.User;import com.tf.service.UserService;public class LoginServlet extends HttpServlet {@Overrideprotected void service(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {response.setCharacterEncoding("UTF-8");String username=request.getParameter("username");String password=request.getParameter("password");System.out.println(username);System.out.println(password);UserService userService=new UserService();User user=userService.getUserByUsernameAndPassword(username, password);request.setAttribute("user", user);if (user!=null) {//请求转发request.getRequestDispatcher("/success.jsp").forward(request, response);//请求重定向  //response.sendRedirect("success.jsp");return;} else {request.getRequestDispatcher("/fail.jsp").forward(request, response);return;}}}

注册：

package com.tf.web.servlet;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import com.tf.entity.User;import com.tf.service.UserService;public class RegisterServlet extends HttpServlet {@Overrideprotected void service(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {response.setCharacterEncoding("UTF-8");String username=request.getParameter("username");String password=request.getParameter("password");System.out.println(username);System.out.println(password);User user = new User();user.setUsername(username);user.setPassword(password);UserService userService=new UserService();if(userService.getUserByUsername(username)!=null){request.getRequestDispatcher("/register.jsp").forward(request, response);return;}else{request.getRequestDispatcher("/login.jsp").forward(request, response);return;}}}

工具类：

package com.tf.util;import java.io.IOException;import java.io.InputStream;import java.sql.Connection;import java.sql.DriverManager;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;import java.util.Properties;public class DBConnectionUtil {//加载连接数据库的驱动//（首先加入jdbc驱动，将解压后的jar包放入lib文件夹中）private static String jdbcDriver="";//客户端的IP地址private static String jdbcURL="";//客户端用户名private static String jdbcUser="";//客户端密码private static String jdbcPassword="";static{InputStream in=DBConnectionUtil.class.getClassLoader().getResourceAsStream("jdbc.properties");Properties p=new Properties();try {p.load(in);jdbcDriver=p.getProperty("jdbcDriver");jdbcURL=p.getProperty("jdbcURL");jdbcUser=p.getProperty("jdbcUser");jdbcPassword=p.getProperty("jdbcPassword");} catch (IOException e) {e.printStackTrace();}}public static Connection getConnection(){Connection conn=null;try {Class.forName(jdbcDriver);conn=DriverManager.getConnection(jdbcURL, jdbcUser, jdbcPassword);} catch (ClassNotFoundException e) {e.printStackTrace();} catch (SQLException e) {e.printStackTrace();}return conn;}public static void closeAll(PreparedStatement ps,Connection conn,ResultSet rs){if(rs!=null){try {rs.close();} catch (SQLException e) {e.printStackTrace();}finally{if(ps!=null){try {ps.close();} catch (SQLException e) {e.printStackTrace();}finally{if(conn!=null){try {conn.close();} catch (SQLException e) {e.printStackTrace();}}        }         }                  }            }      }}