public class IDCard implements Serializable {
 private int id; // 主键
 private String cardCode; // 身份证编号
 private String carAddress; // 身份证地址
 //构造函数及Getter/Setter/toString...
}

public class Person implements Serializable {
 private int id; // 主键
 private String name; // 姓名
 private String sex; // 性别
 private IDCard iDCard; //身份证对象，人和身份证一对一关系
 //构造函数及Getter/Setter/toString...
}

<mapper namespace="pri.xiaoyang.otot.mapper.IDCardMapper">
　　<!-- 根据主键查询IDCard信息，封装为IDCard对象并返回 -->
 <select id="selectIDCardById" pamaeterType="int" resultType="pri.xiaoyang.otot.pojo.IDCard">
  select * from idcard where id = #{id}
 </select>
</mapper>

<mapper namespace="pri.xiaoyang.otot.mapper.PersonMapper">
 <!-- 根据person主键查询Person信息，封装为Person对象并返回 -->
 <select id="selectPersonById" pamaeterType="int" resultMap="PersonMapper">
  select * from person where id = #{id}
 </select>
 
 <!-- 映射Person对象的resultMap -->
 <resultMap type="pri.xiaoyang.otot.pojo.Person" id="PersonMapper">
  <id property="id" column="id" />
  <result property="name" column="name" />
  <result property="sex" column="sex" />
  <!-- 一对一关联映射：association -->
  <association property="iDCard" column="card_id" 
   select="pri.xiaoyang.otot.mapper.IDCardMapper.selectIDCardById"
   javaType="pri.xiaoyang.otot.pojo.IDCard"/>
 </resultMap >
</mapper>