【初学javeEE】如何通过使用数据库实现简单的用户登陆注册页面功能

1. 登陆:
   jsp:

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>










用户名：




密码：

servlet：

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		response.setContentType("text/html;charset=gb2312");
		response.setCharacterEncoding("gb2312");
		request.setCharacterEncoding("UTF-8");
		// TODO Auto-generated method stub
		String user = request.getParameter("user");   //从表单获取用户名
		String pass = request.getParameter("password");   //从表单获取密码
		System.out.println(user+pass);	//测试
		//判断
		if (connectsql(user, pass) == 1){
			response.getWriter().println("登陆成功！"+"Hello " + user + "!");
			response.getWriter().println("
返回登陆页面");
		}
		
			
		else if (connectsql(user, pass) == 2) {
			response.getWriter().println("密码错误！请重新输入");
			response.getWriter().println("
返回登陆页面");
		}
		else {
			response.getWriter().println("登陆失败！"+"Sorry " + user + "!"+"请先进行注册");
			response.getWriter().println("
返回登陆页面");
		}
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}  
	@SuppressWarnings("resource")
	protected int connectsql(String username, String password){
			Connection connection = null;
			PreparedStatement preparedStatement = null;
			ResultSet resultSet = null;
			try {
				Class.forName("com.mysql.cj.jdbc.Driver");				// 加载数据库驱动
				// 通过驱动管理类获取数据库链接
				connection = DriverManager
					.getConnection("jdbc:mysql://localhost:3306/login?serverTimezone=UTC&characterEncoding=utf-8","root", "PdM46t");
				String sql = "select * from record";				// 定义sql语句 
				// 获取预处理statement
				preparedStatement = connection.prepareStatement(sql);
				// 向数据库发出sql执行查询，查询出结果集
				resultSet = preparedStatement.executeQuery();
				// 遍历查询结果集
				while (resultSet.next()) {
					System.out.println(resultSet.getString("user") + "  "
							+ resultSet.getString("password"));
					if (resultSet.getString("user").equals(username))
						if (resultSet.getString("password").equals(password))
							return 1;		//用户名密码正确，返回1
						else
							return 2;		//用户名正确，密码错误，返回2
				}
			} 
			catch (Exception e) {
				e.printStackTrace();
			} finally {
				// 释放资源
				if (resultSet != null) {
					try {
						resultSet.close();
					} catch (SQLException e) {
						// TODO Auto-generated catch block
						e.printStackTrace();
					}
				}
				if (preparedStatement != null) {
					try {
						preparedStatement.close();
					} catch (SQLException e) {
						// TODO Auto-generated catch block
						e.printStackTrace();
					}
				}
				if (connection != null) {
					try {
						connection.close();
					} catch (SQLException e) {
						// TODO Auto-generated catch block
						e.printStackTrace();
					}
				}
			}
			//用户名不存在，返回0
			return 0;
		}

2. 注册：

jsp:

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>










用户名：




密码：

servlet：

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		response.setContentType("text/html;charset=gb2312");
		response.setCharacterEncoding("gb2312");
		request.setCharacterEncoding("UTF-8");
		  String user = request.getParameter("user");   //从表单获取用户名
		String pass = request.getParameter("password");   //从表单获取密码
		//response.getWriter().println(user+pass);	//测试
			connectsql(user,pass);
		  response.getWriter().println("注册成功");
		  response.getWriter().println("
返回登陆页面");
	}
	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}
	protected int connectsql(String username, String password){
		Connection con = null;
		PreparedStatement pstm = null;
		try {
			// 加载数据库驱动
			Class.forName("com.mysql.cj.jdbc.Driver");
			// 通过驱动管理类获取数据库链接
			con= DriverManager
					.getConnection(
							"jdbc:mysql://localhost:3306/login?serverTimezone=UTC&characterEncoding=utf-8",
							"root", "PdM46t");
			String sql = "insert into record(user,password) value(?,?)";
			pstm = con.prepareStatement(sql);
			pstm.setString(1, username);
			pstm.setString(2, password);
			int row = pstm.executeUpdate();
			System.out.println("新增数据为:" + row + "条");
		} 
		catch (ClassNotFoundException e) {
			e.printStackTrace();
		} 
		catch (SQLException e) {
			e.printStackTrace();
		}
		finally{
			if(con != null){
				try {
					con.close();
				} 
				catch (SQLException e) {
					e.printStackTrace();
				}
			}
			if(pstm != null){
				try {
					pstm.close();
				} 
				catch (SQLException e) {
					e.printStackTrace();
				}
			}
		}
		return 0;
	}

数据库：