mybatis用association指定外键结合select实现级联属性查询

最新推荐文章于 2025-07-13 16:54:57 发布

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本文介绍了一个使用MyBatis实现的学生实体与地址实体之间的关联映射案例。通过定义DAO接口和对应的XML映射文件，实现了学生信息的添加及根据ID查找学生及其关联地址的功能。

package com.gewb.dao;
import java.util.List;
import com.gewb.entity.Student;

public interface StudentDao {
public void addStudent(Student student);
// public List<Student> findStudentByAddress(int addressId);
public List<Student> findStudentWithAddress(int id);

}

package com.gewb.dao;
import com.gewb.entity.Address;

public interface AddressDao {
public Address findById(int id);

}

StudentMapper.xml
<?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="com.gewb.dao.StudentDao">

<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.gewb.dao.AddressDao.findById"></association>
</resultMap>

<select id="findStudentWithAddress" parameterType="Integer" resultMap="StudentResult">
select t1.* from student t1,address t2 where t1.addressId = t2.id and t1.id = #{id};
</select>

<insert id="addStudent" parameterType="Student">
insert into student values(null,#{name},#{age});
</insert>

</mapper>

AddressMapper.xml
<?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="com.gewb.dao.AddressDao">

<resultMap type="Address" id="AddressResult">
<id property="eId" column="id"/>
<result property="eProvince" column="province"/>
<result property="eCity" column="city"/>
<result property="eDistrict" column="district"/>
</resultMap>

<select id="findById" parameterType="Integer" resultMap="AddressResult">
select * from address where id = #{id};
</select>
</mapper>