MyBatis 关系映射

 

对象级联(一对一)四种方式（有两张表，一个学生表，一个地址表，一个学生对应一个地址）

实体

/**
*简化写
**/

public class Student {

	private Integer id;
	private String name;
	private Integer age;
	private Address address;
	
	
}

public class Address {

	private Integer id;
	private String sheng;
	private String shi;
	private String qu;
	
	}
	

　　

1.0 （不推荐使用）

<resultMap type="Student" id="StudentResult">
		<id property="id" column="id"/>
		<result property="name" column="name"/>
		<result property="age" column="age"/>
		
		<result property="address.id" column="addressId"/>  addressId是学生表的外键
		<result property="address.sheng" column="sheng"/>
		<result property="address.shi" column="shi"/>
		<result property="address.qu" column="qu"/>
	</resultMap>

　　

2.0（不推荐）

      <resultMap type="Address" id="AddressResult">
		<result property="id" column="id"/>
		<result property="sheng" column="sheng"/>
		<result property="shi" column="shi"/>
		<result property="qu" column="qu"/>
	</resultMap>
	
	<resultMap type="Student" id="StudentResult">
		<id property="id" column="id"/>
		<result property="name" column="name"/>
		<result property="age" column="age"/>
		<association property="address" resultMap="AddressResult"/>
	</resultMap> 

　

3.0（不推荐）

      <resultMap type="Student" id="StudentResult">
		<id property="id" column="id"/>
		<result property="name" column="name"/>
		<result property="age" column="age"/>
		<association property="address" javaType="Address">
			<result property="id" column="id"/>
			<result property="sheng" column="sheng"/>
			<result property="shi" column="shi"/>
			<result property="qu" column="qu"/>
		</association>
	</resultMap>

　　

4.0（推荐）

　　　　<resultMap type="Student" id="StudentResult">
		<id property="id" column="id"/>
		<result property="name" column="name"/>
		<result property="age" column="age"/>
		<association property="address" column="addressId" select="com.java.mappers.AddressMapper.findById"></association> addressId外键
	</resultMap>

　　

 

package com.java.mappers;

import com.java.model.Address;

public interface AddressMapper {

	public Address findById(Integer id);

}