❤️使用Mybatis对数据库进行增删改查！！！

怼烎@ 2023-10-03 15:49 22阅读 0赞

## ❤️使用Mybatis对数据库进行增删改查！！！ ##

## ❤️namespace的用法 ##

namespace中的包名要和接口一致；

## ❤️select用法 ##

*  id：就是对应的namespace的方法名
 *  resultType：sql语句的返回值！
 *  parameterType： 参数类型！

1.  编写接口
2.  编写对应的mapper中的对应语句
3.  测试

## ❤️1.编写接口 ##

package com.kk.dao;
    
    
    import com.kk.pojo.User;
    
    
    import java.util.HashMap;
    import java.util.List;
    import java.util.Map;
    
    public interface UserMapper {
        
    
    
    
        //模糊查询
        List<User> getUserLike(String value);
    
    
        //查询全部用户
        List<User> getUserList();
    
        //根据ID查询用户
        User getUserById(int id);
    
        User getUserById2(HashMap<String, Object> map);
    
        //insert一个用户
        int addUser(User user);
    
        //万能的Map
        int addUser2(Map<String,Object> map);
    
        //修改用户
        int updateUser(User user);
    
        //删除一个用户
        int deleteUser(int id);
    
    }

## ❤️2.编写Mapper.xml ##

<?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE mapper
            PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
            "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
    
    
    <mapper namespace="com.kk.dao.UserMapper">
    
    
        <select id="getUserLike" resultType="com.kk.pojo.User">
            select * from mybatis.user where name like #{value}
    
        </select>
    
    
    
       <select id="getUserList" resultType="com.kk.pojo.User">
            select * from mybatis.user
       </select>
    
        
        <select id="getUserById" parameterType="int" resultType="com.kk.pojo.User" >
            select * from mybatis.user where id = #{id};
        </select>
    
        <select id="getUserById2" parameterType="map" resultType="com.kk.pojo.User" >
            select * from mybatis.user where id = #{helloId} and name=#{name};
        </select>
    
    
        
    
        <insert id="addUser" parameterType="com.kk.pojo.User">
             insert into mybatis.user(id,name,pwd) values(#{id},#{name},#{pwd});
        </insert>
    
    
    
    
    
    
    
    
        
    
        <update id="updateUser" parameterType="com.kk.pojo.User">
            update mybatis.user set name=#{name},pwd=#{pwd} where id = #{id};
        </update>
    
    
        <delete id="deleteUser" parameterType="int">
            delete from mybatis.user where id=#{id}
        </delete>
    
    
    </mapper>

## ❤️3.测试类 ##

package com.kk.dao;
    
    import com.kk.pojo.User;
    import com.kk.util.MybatisUtil;
    
    import org.apache.ibatis.session.SqlSession;
    import org.testng.annotations.Test;
    
    
    import java.util.HashMap;
    import java.util.List;
    
    public class userDaoTest {
        
    
    
        //模糊查询
        @Test
        public  void getUserLike(){
        
            SqlSession sqlSession = MybatisUtil.getSqlSession();
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
    
            List<User> userList = mapper.getUserLike("%王%");
            for (User user : userList) {
        
                System.out.println(user);
            }
    
            sqlSession.close();
        }
    
    
    
    
        @Test
        public void test(){
        
            //第一步：获得SqlSession对象
            SqlSession sqlSession = MybatisUtil.getSqlSession();
            try {
        
                //方式一：执行SQL-->getMapper
                UserMapper mapper = sqlSession.getMapper(UserMapper.class);
                List<User> userList = mapper.getUserList();
                for (User user : userList) {
        
                    System.out.println(user);
                }
    
    
            }catch (Exception e){
        
                 e.printStackTrace();
            }finally {
        
                //关闭sql
                sqlSession.close();
            }
    
        }
    
    
        @Test
        public void getUserId(){
        
            SqlSession sqlSession = MybatisUtil.getSqlSession();//通过MybatisUtil获得Sql Seesion
    
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);//通过这个获得UserMapper这个接口
    
            User user = mapper.getUserById(1);
    
            System.out.println(user);
    
            sqlSession.close();
        }
    
    
        @Test
        public void getUserId2(){
        
            SqlSession sqlSession = MybatisUtil.getSqlSession();//通过MybatisUtil获得Sql Seesion
    
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);//通过这个获得UserMapper这个接口
    
            HashMap<String, Object> map = new HashMap<>();
            map.put("helloId",1);
            User user = mapper.getUserById2(map);
    
            System.out.println(user);
    
            sqlSession.close();
        }
    
        //增删改需要提交事务
        @Test
        public void addUser(){
        
            SqlSession sqlSession = MybatisUtil.getSqlSession();
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            int res = mapper.addUser(new User(4, "大白", "123456"));
            if (res>0){
        
                System.out.println("插入成功！");
            }
    
            //提交事务
            sqlSession.commit();
    
            sqlSession.close();
        }
    
        //增删改需要提交事务 Map
        @Test
        public void addUser2(){
        
            SqlSession sqlSession = MybatisUtil.getSqlSession();
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
    
            HashMap<String, Object> map = new HashMap<>();
            map.put("userid",6);
            map.put("userName","程峰");
            map.put("passWord","666666");
    
            mapper.addUser2(map);
    
            //提交事务
            sqlSession.commit();
    
            sqlSession.close();
        }
    
    
        @Test
        public void updateUser(){
        
            SqlSession sqlSession = MybatisUtil.getSqlSession();
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            mapper.updateUser(new User(5,"晓晓","123789"));
            sqlSession.commit();
            sqlSession.close();
        }
    
        @Test
        public void deleteUser(){
        
            SqlSession sqlSession = MybatisUtil.getSqlSession();
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            mapper.deleteUser(4);
    
            sqlSession.commit();
            sqlSession.close();
        }
    
    
    
    
    
    }
    
    
    //        //方式二：
    //        List<User> userList = sqlSession.selectList("com.kk.UserDao.getUserList");

注意点：增删改需要提交事务。

#### \#\# Map用法 ####

假如我们的实体类属性过多，用map，传递map的key

接口

User getUserById2(HashMap<String, Object> map);

Mapper.xml

<select id="getUserById2" parameterType="map" resultType="com.kk.pojo.User" >
        select * from mybatis.user where id = #{helloId} and name=#{name};
    </select>

测试

@Test
        public void getUserId2(){
        
            SqlSession sqlSession = MybatisUtil.getSqlSession();//通过MybatisUtil获得Sql Seesion
    
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);//通过这个获得UserMapper这个接口
    
            HashMap<String, Object> map = new HashMap<>();
            map.put("helloId",1);
            User user = mapper.getUserById2(map);
    
            System.out.println(user);
    
            sqlSession.close();
        }

## ❤️4.模糊查询 ##

java代码执行的时候，传递通配符%

接口

//模糊查询
    List<User> getUserLike(String value);

Mapper.xml

<select id="getUserLike" resultType="com.kk.pojo.User">
            select * from mybatis.user where name like #{value}
    
        </select>

测试

//模糊查询
     @Test
        public  void getUserLike(){
        
            SqlSession sqlSession = MybatisUtil.getSqlSession();
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
    
            List<User> userList = mapper.getUserLike("%王%");
            for (User user : userList) {
        
                System.out.println(user);
            }
    
            sqlSession.close();
        }