MyBatis——增删改查（CRUD）

准备工作：创建在com.jiang.pojo中创建实体类

package com.jiang.pojo;

import lombok.Data;


//实体类

@Data
public class User {
    private int id;
    private String name;
    private String pwd;


}

1、namespace

namespace中的包名要和 Dao/mapper 接口的包名一致！

2、select

选择，查询语句;

• id : 就是对应的namespace中的方法名；
• resultType：Sql语句执行的返回值！
• parameterType ： 参数类型！

1. 编写UserMapper接口

   //根据ID查询用户
   User getUserById(int id);

2. 编写对应的UserMapper中的sql语句

   <select id="getUserById" parameterType="int" resultType="com.jiang.pojo.User">
           select * from mybatis.user where id = #{id}
   </select>
   

3. 测试

       @Test
       public void getUserById() {
           SqlSession sqlSession = MybatisUtils.getSqlSession();
   
           UserMapper mapper = sqlSession.getMapper(UserMapper.class);
   
           User user = mapper.getUserById(1);
           System.out.println(user);
   
           sqlSession.close();
       }
   

3、Insert

1. 编写UserMapper接口

   //insert一个用户
       int addUser(User user);

2. 编写对应的UserMapper中的sql语句

    <insert id="addUser" parameterType="com.jiang.pojo.User">
           insert into mybatis.user (id, name, pwd) values (#{id},#{name},#{pwd});
       </insert>

3. 测试

   package com.jiang.dao;
   
   import com.jiang.pojo.User;
   import com.jiang.utils.MybatisUtils;
   import org.apache.ibatis.session.SqlSession;
   import org.junit.Test;
   
   import java.util.List;
   
   public class UserDaoTest {
   
       @Test
       public void getUserLike(){
           SqlSession sqlSession = MybatisUtils.getSqlSession();
   
           UserMapper mapper = sqlSession.getMapper(UserMapper.class);
   
           int i = mapper.addUser(new User(5, "姜嘉航","465123"));
           if (i>0){
               System.out.println("插入成功");
           }
           //提交事务
           sqlSession.commit();
           sqlSession.close();
       }
   
   
   }
   

4、update

1. 编写UserMapper接口

      //修改用户
       int updateUser(User user);

2. 编写对应的UserMapper中的sql语句

       <update id="updateUser" parameterType="com.jiang.pojo.User">
           update mybatis.user set name=#{name},pwd=#{pwd}  where id = #{id} ;
       </update>

3. 测试

   package com.jiang.dao;
   
   import com.jiang.pojo.User;
   import com.jiang.utils.MybatisUtils;
   import org.apache.ibatis.session.SqlSession;
   import org.junit.Test;
   
   import java.util.List;
   
   public class UserDaoTest {
   
       @Test
       public void getUserLike(){
           SqlSession sqlSession = MybatisUtils.getSqlSession();
   
           UserMapper mapper = sqlSession.getMapper(UserMapper.class);
   
           int i = mapper.updateUser(new User(5, "哈哈","1265123"));
           if (i>0){
               System.out.println("更新成功");
           }
           //提交事务
           sqlSession.commit();
           sqlSession.close();
       }
   
   
   }
   

5、Delete

1. 编写UserMapper接口

       //删除一个用户
       int deleteUser(int id);

2. 编写对应的UserMapper中的sql语句

       <delete id="deleteUser" parameterType="int">
           delete from mybatis.user where id = #{id};
       </delete>

3. 测试

   package com.jiang.dao;
   
   import com.jiang.pojo.User;
   import com.jiang.utils.MybatisUtils;
   import org.apache.ibatis.session.SqlSession;
   import org.junit.Test;
   
   import java.util.List;
   
   public class UserDaoTest {
   
       @Test
       public void getUserLike(){
           SqlSession sqlSession = MybatisUtils.getSqlSession();
   
           UserMapper mapper = sqlSession.getMapper(UserMapper.class);
   
           mapper.deleteUser(5);
           System.out.println("删除成功");
           sqlSession.commit();
           sqlSession.close();
       }
   
   
   }
   

注意点：

• 增删改需要提交事务！（ sqlSession.commit();）