UserMapper.xml中namespace的值要與mapper.java的完全限定地址一樣

<?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="zzu.qg.mybatis.dao.UserMapper">
	<select id="findUserById" parameterType="int" resultType="zzu.qg.mybatis.entity.User">
		select * from [user] where id=#{value}
	</select>
	
	<insert id="insertUser" parameterType="zzu.qg.mybatis.entity.User">
		insert into [user] values(#{userName},#{password},#{sex},#{birthday})
	</insert>
</mapper>
 

UserMapper.java  方法名，，輸入引數型別，，返回值型別

public interface UserMapper {
	
	public User findUserById(int id);
	
	public void insertUser(User user);
	
}

測試類

public class TestUserDao {
	
	
	private SqlSessionFactory sqlSessionFactory;
	private InputStream inputStream;
	@Before
	public void initSqlSessionFactory(){
		String resource="config/mybatis/mybatis-config.xml";
		try {
			inputStream = Resources.getResourceAsStream(resource);
		} catch (IOException e) {
			e.printStackTrace();
		}
		sqlSessionFactory=new SqlSessionFactoryBuilder().build(inputStream);
		
	}
	
	@Test
	public void testFindUserById(){
		SqlSession sqlSession=sqlSessionFactory.openSession();
		//將mapper介面的位元組碼物件當作引數傳給sqlSession.getMapper()，sqlSession自動建立mapper介面的代理物件
		UserMapper userMapper=sqlSession.getMapper(UserMapper.class);
		User user=userMapper.findUserById(1);
		System.out.println(user);
		sqlSession.close();
	}
	
	@Test
	public void testInsertUser(){
		SqlSession sqlSession=sqlSessionFactory.openSession();
		//將mapper介面的位元組碼物件當作引數傳給sqlSession.getMapper()，sqlSession自動建立mapper介面的代理物件
		UserMapper userMapper=sqlSession.getMapper(UserMapper.class);
		User user=new User("張三","suibianle","女","2000-9-23");
		userMapper.insertUser(user);
		sqlSession.commit();
		System.out.println(user.getId());
		
		sqlSession.close();
	}
}
 

定義完mapper對映檔案後，接下來就要開發mapper介面，編寫mapper介面需要遵循以下四個基本規範：

1、在mapper.xml中namespace的值等於mapper介面的完全限定地址

2、mapper.java中的方法名要與mapper.xml的statement的id一致

3、mapper.java中的方法輸入引數型別要與mapper.xml的parameterType的型別一致

4、mapper.java中的返回值型別要與mapper.xml的resultType的型別一致(注意：resultType指的是返回單個結果的型別)

執行結果：

執行testFindUserById時

執行insertUser時