1需求:根据id查询学生的身份证信息
学生实体Bean
public class Student { private Integer id; private String name; private Card card; //关联的身份证对象
学生的Mapper(注意当学生类中包含其他类的bean对象时映射的写法!! 学生类中包含了 Card对象)
<?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.cn.entity2.Student" > <resultMap id="studentMapper" type="com.cn.entity2.Student"> <id property="id" column="id"></id> <result property="name" column="name"></result> <association property="card" resultMap="com.cn.entity2.Card.cardMapper"></association> </resultMap> <select id="findByid" parameterType="int" resultMap="studentMapper"> select s.id,s.name,c.cid,c.cunm from student s inner join cards c on s.scid = c.cid and s.id = #{id} </select> </mapper>
身份证Bean
public class Card { private Integer cid; private String cunm;
身份证Mapper
<?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.cn.entity2.Card" > <resultMap id="cardMapper" type="com.cn.entity2.Card"> <id property="cid" column="cid"></id> <result property="cunm" column="cunm"></result> </resultMap> </mapper>