基于Servlet+MyBatis实现登录注册案例

项目分层

• java
  • mapper
    • UserMapper
  • pojo
    • User
  • web
    • LoginServlet
    • RegisterServlet
• resources
  • mapper
    • Mybatis-config.xml
• webapp
  • css
  • imgs
  • WEB-INF
    • Index-jsp
    • login.html
    • register.html

1. mapper/UserMapper.java(Interface 映射层 实现对数据库的操作)

package mapper;

import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;
import pojo.User;

public interface UserMapper {
    //根据用户名和密码查询用户对象
    @Select("select * from tb_user where username = #{username} and password = #{password}")
    User select(@Param("username") String username, @Param("password") String password);

    //根据用户名查询用户对象
    @Select("select * from tb_user where username = #{username}")
    User selectByUsername(String username);

    //添加用户
    @Insert("insert into tb_user values(null,#{username},#{password})")
    void add(User user);
}

2.pojo/User.java(基本类 封装User对象及所需方法)

package pojo;

public class User {

    private Integer id;
    private String username;
    private String password;

    public Integer getId() {
        return id;
    }

    public void setId(Integer 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;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                '}';
    }
}

3.web/LoginServlet.java(用户登录逻辑)

package web;

import mapper.UserMapper;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import pojo.User;

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;

@WebServlet("/loginServlet")
public class LoginServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1.接收用户名和密码
        String username = request.getParameter("username");
        String password = request.getParameter("password");

        //2.调用MyBatis完成查询
        //2.1 获取SqlSessionFactory对象
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        //2.2 获取SqlSession对象
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //2.3 获取Mapper
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        //2.4 调用方法
        User user = userMapper.select(username, password);
        //2.5 释放资源
        sqlSession.close();

        //获取字符输出流，并设置对应的content type
        response.setContentType("text/html;charset=utf-8");
        PrintWriter writer = response.getWriter();
        //3.判断user是否为null
        if (user!=null){
            //登录成功
            writer.write("<h1>登录成功</h1>");
        }else{
            //登录失败
            writer.write("<h1>登录失败</h1>");

        }
    }

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

4.web/RegisterServlet.java(用户注册逻辑/需要在sql中增加记录，记得提交事务)

package web;

import mapper.UserMapper;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import pojo.User;

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
import java.io.InputStream;

@WebServlet("/registerServlet")
public class RegisterServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String username = request.getParameter("username");
        String password = request.getParameter("password");

        User user = new User();
        user.setUsername(username);
        user.setPassword(password);

        //2.调用MyBatis完成查询
        //2.1 获取SqlSessionFactory对象
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        //2.2 获取SqlSession对象
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //2.3 获取Mapper
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);

        //调用方法
        User u = userMapper.selectByUsername(username);
        response.setContentType("text/html;charset=utf-8");

        if (u==null){
            response.getWriter().write("<h1>用户添加成功！</h1>");
            //用户不存在
            userMapper.add(user);
            //!!!!提交事务！！！！因为涉及到增删改的操作了
            sqlSession.commit();
            sqlSession.close();
        }else{
            //用户存在
            response.getWriter().write("<h1>用户名已经存在</h1>");
        }
    }

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