MyBatis SQL mapper mapper

1. If you use the Mapper mapper, how do you only need to write the interface, without writing the implementation, the framework is automatically generated

2. Specification:
   2.1 Traditional Dao interface, now the name ends with Mapper: For example: IUserDao-> UserMapper
   2.2 Put UserMapper interface and mapping file UserMapper.xml in cn.itsource.mapper

3. Implementation steps:
   3.1. Create a new package cn.itsource.mapper, create a new interface [ProductMapper] in the package and
   directly go to IProductDao to copy
   3.2. In package cn.itsource.mapper, create a new mapping file [ProductMapper.xml] The content is copied to the xml in the domain package, and the namespace is modified to cn.itsource.mapper.ProductMapper
   3.3. Load the mapper mapping file in the main configuration file

4. Functional test: query a single object:

SqlSession session = MybatisUtil.getSession();
//接口不能实例化  -- 框架帮我们实现了的（只不过不需要去管怎么实现，甚至你连实现类的名字都不知道），然后通过多态的方式进行接收
ProductMapper mapper = session.getMapper(ProductMapper.class);//获取接口的代理对象
System.out.println(mapper.loadOne(1l));

5. Modify:

@Test
public void testUpdate(){
	SqlSession session = MybatisUtil.getSession();
	ProductMapper mapper = session.getMapper(ProductMapper.class);
		
	Product old = mapper.loadOne(1l);
	System.out.println("更新之前：" + old);
		
	old.setProductName("AD钙奶");
	mapper.update(old);
	session.commit();//提交事务
		
	Product now = mapper.loadOne(1l);
	System.out.println("更新之后：" + now);
}