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();
 //        }
 //    }
 }

UserDao

 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();
 //        }
 //    }
 }

UserServlet

 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();
             }
         }
     }
 }

ConnectionUtil

 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) {
     }
 }

DBCloseListener

 <?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>

Maven