mabatis mapper开发规范

定义一个mapper接口

package mapper;

import pojo.User;

public interface UserMapper {
    public User getUser(int id) throws Exception;
    public void insertUser(User user) throws Exception;
}

定义一个UserMapper.xml指向它，注意namespace需要指向它的全路径，sql语句id同方法名，然后入参和结果都和方法入参，返回一致。

xml名称不一定要和接口名相同，它是通过namespace搜索的。

<?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="mapper.UserMapper">
    <select id="getUser" parameterType="int"
        resultType="User">
        select id, name, age, gmt_create gmtCreate from users where id=#{id}
    </select>
    
    <insert id="insertUser" parameterType="User">
        <selectKey keyProperty="id" order="AFTER" resultType="java.lang.Integer">
            SELECT LAST_INSERT_ID()
        </selectKey>
        insert into users(name, age, gmt_create, money) VALUE ('xiao', 24, '1991-06-26', 10000)
    </insert>

测试

private SqlSessionFactory sqlSessionFactory;
	
	@Before
	public void setUp() throws Exception{
		sqlSessionFactory = MybatisUtils.getFactory();
	}

	@Test
	public void testGetUser() throws Exception{
		SqlSession sqlSession = sqlSessionFactory.openSession();
		UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
		User user = userMapper.getUser(1);
		System.out.println(user);
	}

通过sqlSession.getMapper返回代理类。

根据返回的参数智能选择使用selectOne或selectList，即程序员可以定义

public User getUser(int id) throws Exception;
public List<User> getUserByName(String userName) throws Exception;