查

1,编写接口方法

public interface userMapper {
    //根据ID查询用户
    User getUserByID(int id);
}

2，编写Mapper中sql语句

        select * from user where id= #{id}
    

3，实现

public void getUserByID(){
        SqlSession sqlSession = sqlSessionFactory.getsqlSession();
        userMapper mapper = sqlSession.getMapper(userMapper.class);
        User userByID = mapper.getUserByID(1);
        System.out.println(userByID);
        sqlSession.close();
    }

增

1.编写接口中的方法

int addUser (User user);

2.编写Mapper中的sql语句

    
        insert into user (id,name,pwd) value (#{id},#{name},#{pwd})
    

3.实现

 public void addUser (){
        SqlSession sqlSession = sqlSessionFactory.getsqlSession();
        userMapper mapper = sqlSession.getMapper(userMapper.class);
        int nums = mapper.addUser(new User(4, "秋君", "123123"));
        if(nums>0){
            sqlSession.commit();//提交事务(增删改都需要提交事务)
        }
    }

删

1.编写接口中的方法

int deleteUser (int id);

2.编写Mapper中的sql语句

 
    
        delete from user where id=#{id}
    

3.实现

public void deleteUser(){
        SqlSession sqlSession = sqlSessionFactory.getsqlSession();
        userMapper mapper = sqlSession.getMapper(userMapper.class);
        int nums = mapper.deleteUser(4);
        if(nums>0){
            sqlSession.commit();
        }
        sqlSession.close();
    }

改

1.编写接口中的方法

int updateUser (User user);

2.编写Mapper中的sql语句

  
    
        update user
        set name=#{name},pwd=#{pwd}
        where id=#{id};
    

3.实现

public void updateUser(){
        SqlSession sqlSession = sqlSessionFactory.getsqlSession();
        userMapper mapper = sqlSession.getMapper(userMapper.class);
        int nums = mapper.updateUser(new User(4, "小罗", "123123123"));
        if(nums>0){
            sqlSession.commit();
        }
    }

注意，增删改需要提交事务（commit）