servlet-mysql实现简单用户登录注册

环境：IDEA Maven

效果截图：

项目结构：

类说明：

ConnectionUtil：负责数据库连接和释放

UserDao：数据库增删改查操作

User：用户Bean，只用注册和登录的话可以不要

UserServlet：Servlet，控制页面跳转

前端就不放了大同小异

import cn.flyuz.pan.entity.User;
import cn.flyuz.pan.util.Base;
import cn.flyuz.pan.util.ConnectionUtil;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class UserDao {
    private Connection getConn() {
        ConnectionUtil connectionUtil = new ConnectionUtil();
        return connectionUtil.getConn();
    }
    public boolean login(String user, String pw) {
        Connection conn = getConn();
        String sql = "select * from login where user=? and pw=?";

        try {
            PreparedStatement ps =conn.prepareStatement(sql);
            ps.setString(1,user);
            ps.setString(2,pw);
            ResultSet rs = ps.executeQuery();
            if (rs.next()){
                ps.close();
                rs.close();
                return true;
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return false;
    }

    public String reg(String user, String pw) {
        Connection conn = getConn();
        String sql1= "select * from login where user = ?";
        String sql = "insert into login(user,pw) values (?,?)";

        try {
            PreparedStatement pss = conn.prepareStatement(sql1);
            pss.setString(1,user);
            ResultSet rs = pss.executeQuery();
            if (!rs.next()){
                PreparedStatement ps = conn.prepareStatement(sql);
                ps.setString(1,user);
                ps.setString(2,pw);
                ps.executeUpdate();
                return Base.registerSuccess;
            }else{
                return Base.registerFalse;
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return Base.registerFalse;
    }

    public void del(String user) {
        Connection conn = getConn(); //获取连接
        String sql = "delete from login where user = ?";//sql语句
        try {
            PreparedStatement ps = conn.prepareStatement(sql);
            ps.setString(1,user);
            ps.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
//    public List<User> getAll() {
//        Connection conn = getConn();
//        String sql = "select * from login";
//        try {
//            PreparedStatement ps = conn.prepareStatement(sql);
//            ResultSet rs = ps.executeQuery();
//            List<User> userList = new ArrayList<>();
//            while(rs.next()) {
//                User user1 = new User();
//                user1.setUser(rs.getString("user"));
//                user1.setPw(rs.getString("pw"));
//                userList.add(user1);
//            }
//            return userList;
//        } catch (SQLException e) {
//            e.printStackTrace();
//        }
//        return null;
//    }
//    public void update(String user,String pw){
//        Connection conn = getConn(); //获取连接
//        String sql = "update login set user = ?,pw = ? where id = ?"; //sql语句
//        try {
//            PreparedStatement ps = conn.prepareStatement(sql);
//            //设置参数
//            ps.setString(1,user);
//            ps.setString(2,pw);
//            ps.executeUpdate();
//
//        } catch (SQLException e) {
//            e.printStackTrace();
//        }
//    }
}

import cn.flyuz.pan.dao.UserDao;
import cn.flyuz.pan.util.Base;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;


@WebServlet(name = "UserServlet", urlPatterns = "/loginServlet")
public class UserServlet extends HttpServlet {
    private UserDao userDao = new UserDao();

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=utf-8");
        request.setCharacterEncoding("utf-8");
        String type = request.getParameter("type");

        switch (type) {
            case "login":
                login(request, response);
                break;
            case "reg":
                reg(request, response);
                break;
//            case "del":
//                del(request, response);
//                break;
//            case "getAll":
//                getAll(request, response);
//                break;
        }
    }
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }


    private void login(HttpServletRequest request, HttpServletResponse response) {
        String user = request.getParameter("user");
        String pw = request.getParameter("pw");

        boolean user_login = userDao.login(user, pw);
        try {
            if (user_login) {
                request.getRequestDispatcher("index/index.jsp").forward(request, response);
            } else {
                String msg = "登陆失败";
                request.getSession().setAttribute("msg", msg);
                request.getRequestDispatcher("index/login.jsp").forward(request, response);
            }
        } catch (ServletException | IOException e) {
            e.printStackTrace();
        }
    }

    private void reg(HttpServletRequest request, HttpServletResponse response) {
        String user = request.getParameter("user");
        String pw = request.getParameter("pw");

        String rs = userDao.reg(user, pw);
        if (rs.equals(Base.registerSuccess)) {
            try {
                request.getRequestDispatcher("index/login.jsp").forward(request, response);
            } catch (ServletException | IOException e) {
                e.printStackTrace();
            }
        } else if (rs.equals(Base.registerFalse) || rs.equals(Base.registerRepeated)) {
            try {
                String msg = "注册失败";
                request.getSession().setAttribute("msg", msg);
                request.getRequestDispatcher("index/register.jsp").forward(request, response);
            } catch (ServletException | IOException e) {
                e.printStackTrace();
            }
        }
    }
//    private void del(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//        String user = request.getParameter("user");
//        try {
//            userDao.del(user);
//            request.getSession().setAttribute("msg", "删除成功！");
//            request.getRequestDispatcher("index/index.jsp").forward(request, response);
//        } catch (Exception e) {
//            e.printStackTrace();
//            request.getSession().setAttribute("msg", "删除失败！");
//            request.getRequestDispatcher("index/index.jsp").forward(request, response);
//        }
//    }
//    private void getAll(HttpServletRequest request, HttpServletResponse response) {
//        request.getSession().setAttribute("userList", userDao.getAll());
//        try {
//            request.getRequestDispatcher("index/index.jsp").forward(request, response);
//        } catch (ServletException | IOException e) {
//            e.printStackTrace();
//        }
//    }
}

import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Connection;

public class ConnectionUtil {
    private String dbDriver = "com.mysql.cj.jdbc.Driver";
    private String dbUrl="jdbc:mysql://localhost:3306/login?characterEncoding=utf-8&useSSL=false&serverTimezone=UTC ";
    private String dbUser="root";
    private String dbPw="123456";
    private static Connection conn = null;

    public Connection getConn() {
        try{
            Class.forName(dbDriver);
            conn = DriverManager.getConnection(dbUrl,dbUser,dbPw);
        }catch(ClassNotFoundException|SQLException e){
            e.printStackTrace();
        }
        return conn;
    }

    public static void conClose(){
        if(conn != null){
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

import cn.flyuz.pan.util.ConnectionUtil;

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.annotation.WebListener;

@WebListener
public class DBCloseListener implements ServletContextListener{
    @Override
    public void contextDestroyed(ServletContextEvent arg0) {
        ConnectionUtil.conClose();
    }

    @Override
    public void contextInitialized(ServletContextEvent arg0) {
    }
}

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>groupId</groupId>
    <artifactId>flyuzP</artifactId>
    <version>1.0-SNAPSHOT</version>
    <dependencies>
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>jstl</artifactId>
        <version>1.2</version>
    </dependency>

    <dependency>
        <groupId>taglibs</groupId>
        <artifactId>standard</artifactId>
        <version>1.1.2</version>
    </dependency>

    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>8.0.12</version>
    </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>2.5</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                    <encoding>utf8</encoding>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>