mybatis-day02

resultMap

使用resultType要求列名和属性名一致，不过不一致就无法创建映射，我们可以使用resultMap来解决这种问题

	
	
	


	select id id_,username username_,birthday birthday_ from user 

List list = mapper.findAllUser();

一对一

方式一：新建类A 继承已有的类B，再把C的属性放到A中

Orders>User 一对一

public class OrdersCustom extends Orders {

	private int uid;
	private String username;
	private Date birthday;
	private String sex;
	private String address;
}

	select orders.*,user.id uid,user.username,user.birthday,user.sex,user.address
	from orders,user 
	where orders.user_id=user.id

SqlSession session = factory.openSession();
UserMapper mapper = session.getMapper(UserMapper.class);

List list = mapper.findAllOrders();

方式二：在类A中加入属性类B

public class Orders {
    private Integer id;

    private Integer userId;

    private String number;

    private Date createtime;

    private String note;
    
    private User user;
}

	
	
	
	
	
	
	
		
		
		
		
		
		
	


	select orders.*,user.id uid,user.username,user.birthday,user.sex,user.address
	from orders,user 
	where orders.user_id=user.id

SqlSession session = factory.openSession();
UserMapper mapper = session.getMapper(UserMapper.class);

List list = mapper.findAllOrders2();

一对多

在一方加入属性多

public class User {
	private int id;
	private String username;
	private Date birthday;
	private String sex;
	private String address;
	
	private List ordersList;
}

SQL

	
	
	
	
	
	
	
	
		
		
		
		
		
	


	select user.*,b.id oid ,user_id, number, createtime 
	 from user,orders b where user.id=b.user_id

java

SqlSession session = factory.openSession();
UserMapper mapper = session.getMapper(UserMapper.class);

List list = mapper.findAllUsers();

#与$的区别？#

mybatis和hibernate的区别

源码

https://gitee.com/ssmcqc/cuimybatis01