MyBatis多对一，一对多，多对多，一对多关联查询

一、Person实体类

public class Person {
    private Integer personId;
    private String name;
    private Integer gender;
    private String personAddr;
    private Date birthday;  
    //与订单的关系是一对多
    private List<Orders> orderList;
    //与角色是一对多关系
    private List<Role> roleList;  
    //与身份证是一对一关系
    private IdCard ic;
}

二、mapper映射文件相关配置

<!-- =====================一对多关联查询============================ -->
  <resultMap type="person" id="selectOrderByPersonIdRm" extends="BaseResultMap">
      <collection property="orderList" ofType="cn.tx.model1.Orders">
          <id column="ORDER_ID" property="orderId" jdbcType="INTEGER" />
        <result column="PERSON_ID" property="personId" jdbcType="INTEGER" />
        <result column="TOTAL_PRICE" property="totalPrice" jdbcType="REAL" />
        <result column="ADDR" property="addr" jdbcType="VARCHAR" />
      </collection>
  </resultMap>
  <select id="selectOrderByPersonId" parameterType="int" resultMap="selectOrderByPersonIdRm">
      SELECT * from person p, orders o where p.PERSON_ID = o.PERSON_ID and p.PERSON_ID = #{personId};
  </select>

<resultMap type="person" id="selectOrderAndDetailByPersonIdRM" extends="BaseResultMap">
      <collection property="orderList" ofType="cn.tx.model1.Orders">
          <id column="ORDER_ID" property="orderId" jdbcType="INTEGER" />
        <result column="PERSON_ID" property="personId" jdbcType="INTEGER" />
        <result column="TOTAL_PRICE" property="totalPrice" jdbcType="REAL" />
        <result column="ADDR" property="addr" jdbcType="VARCHAR" />
        <collection property="detailList" ofType="cn.tx.model1.OrderDetail">
            <id column="DETAIL_ID" property="detailId" jdbcType="INTEGER" />
            <result column="ORDER_ID" property="orderId" jdbcType="INTEGER" />
            <result column="ITEM_NAME" property="itemName" jdbcType="VARCHAR" />
            <result column="PRICE" property="price" jdbcType="REAL" />
            <result column="QUANTITY" property="quantity" jdbcType="INTEGER" />
        </collection>
      </collection>
  </resultMap>
  <select id="selectOrderAndDetailByPersonId" parameterType="int" resultMap="selectOrderAndDetailByPersonIdRM">
      SELECT * from person p, orders o,order_detail od where p.PERSON_ID = o.PERSON_ID and o.ORDER_ID = od.ORDER_ID and p.PERSON_ID = #{personId}
  </select>

<resultMap type="person" id="selectPersonAndRoleByPersonIdRM" extends="BaseResultMap">
      <collection property="roleList" ofType="cn.tx.model1.Role">
          <id column="ROLE_ID" property="roleId" jdbcType="INTEGER" />
        <result column="ROLE_NAME" property="roleName" jdbcType="VARCHAR" />
        <result column="DESCPRIT" property="descprit" jdbcType="VARCHAR" />
      </collection>
  </resultMap>
  <select id="selectPersonAndRoleByPersonId" parameterType="int" resultMap="selectPersonAndRoleByPersonIdRM">
      SELECT * from person p,person_role pr,role r where p.PERSON_ID=pr.PERSON_ID AND pr.ROLE_ID=r.ROLE_ID AND p.PERSON_ID=#{id}
  </select>