Mybatis查询复杂对象（对象包括对象和List<对象>）

之前有遇到这么一个问题，通过ID查找查找一个复杂对象，由几个表格的数据共同组成。

开发的时候，采用的方法是，先查主表，再根据外键查从表。

这样增加了与数据库的查询次数，数据量大的时候效率不理想。

于是进行了优化，一次性查出所有的表的数据并拼成复杂对象，dao层接收。

代码如下：

<!-- 一次性导出现金申报书所有关联信息 --><resultMap type="com.fiberhome.ms.cus.cashform.entity.CashformReturn" id="ResultMap">  <id property="id" column="ID" />  //必须提出来作为区分数据的关键，一个ID一条数据        <association property="cashform"  javaType="com.fiberhome.ms.cus.cashform.entity.Cashform" resultMap="CashformResultMap" />          <association property="formHead"  javaType="com.fiberhome.ms.cus.cashform.entity.CashformDetail" resultMap="DetailResultMap" />          <collection property="formBody" ofType="com.fiberhome.ms.cus.cashform.entity.CashformList"  resultMap="ListResultMap" />      </resultMap>          <resultMap type="com.fiberhome.ms.cus.cashform.entity.Cashform" id="CashformResultMap">    <id property="id" column="ID" />          <result property="formId" column="FORM_ID" />          <result property="formSerialNum" column="FORM_SERIAL_NUM" />          <result property="port" column="PORT" />          <result property="formNumber" column="FORM_NUMBER" />          <result property="state" column="STATE" />          <result property="cashFormCategory" column="CASH_FORM_CATEGORY" />          <result property="flag" column="FLAG" />          <result property="enterDate" column="ENTER_DATE" jdbcType="DATE" />          <result property="scanDate" column="SCAN_DATE" jdbcType="DATE" />      </resultMap>       <resultMap type="com.fiberhome.ms.cus.cashform.entity.CashformDetail" id="DetailResultMap">          <id property="id" column="detailId" />          <result property="cashFormId" column="secondCashFormId" />          <result property="sourPlace" column="SOUR_PLACE" />          <result property="desPlace" column="DES_PLACE" />          <result property="placeDate" column="PLACE_DATE" />          <result property="name" column="NAME" />          <result property="sex" column="SEX" />          <result property="country" column="COUNTRY" />          <result property="birthplace" column="BIRTHPLACE" />          <result property="birthday" column="BIRTHDAY" jdbcType="DATE" />          <result property="certificateCategory" column="CERTIFICATE_CATEGORY" />          <result property="signDate" column="SIGN_DATE" jdbcType="TIMESTAMP" />          <result property="idNumber" column="ID_NUMBER" />          <result property="issuePlace" column="ISSUE_PLACE" />          <result property="customsSignature" column="CUSTOMS_SIGNATURE" />          <result property="placeAndPhone" column="PLACE_AND_PHONE" />          <result property="phone" column="PHONE" />          <result property="flag" column="detailFlag" />          <result property="formId" column="cashFormFormId" />          <result property="cashFormCategory" column="cashCaregory" />      </resultMap>  <resultMap id="ListResultMap" type="com.fiberhome.ms.cus.cashform.entity.CashformList" >    <id column="cashformListId" property="id" jdbcType="BIGINT" />    <result column="thirdCashFormId" property="cashFormId" jdbcType="INTEGER" />    <result column="CASH_TYPE" property="cashType" jdbcType="NVARCHAR" />    <result column="CURRENCY_TYPE" property="currencyType" jdbcType="NVARCHAR" />    <result column="CURRENCY_VALUE" property="currencyValue" jdbcType="NVARCHAR" />    <result column="listFlag" property="flag" jdbcType="NVARCHAR" />    <result column="OTHER" property="other" jdbcType="NVARCHAR" />    <result column="ISORNOT" property="isornot" jdbcType="BIT" />    <collection property="third" ofType="com.fiberhome.ms.cus.cashform.entity.CashformThird"  resultMap="thirdResultMap" /></resultMap><resultMap id="thirdResultMap" type="com.fiberhome.ms.cus.cashform.entity.CashformThird">        <result property="id" column="thirdId" jdbcType="BIGINT" />        <result property="cashFormListId" column="CASH_FORM_LIST_ID" jdbcType="BIGINT" />        <result property="ownerType" column="OWNER_TYPE" jdbcType="VARCHAR" />        <result property="ownerNameLaw" column="OWNER_NAME_LAW" jdbcType="VARCHAR" />        <result property="ownerName" column="OWNER_NAME" jdbcType="VARCHAR" />        <result property="ownerSex" column="OWNER_SEX" jdbcType="VARCHAR" />        <result property="ownerAddress" column="OWNER_ADDRESS" jdbcType="VARCHAR" />        <result property="flag" column="thirdFlag" jdbcType="VARCHAR" /></resultMap><select id = "selectCashformAllInfo" resultMap="ResultMap">SELECT T.* FROM (SELECT A.ID,A.FORM_ID,A.PORT,A.FORM_SERIAL_NUM,A.FORM_NUMBER,A.STATE,A.CASH_FORM_CATEGORY,A.ENTER_DATE,A.SCAN_DATE,A.FLAG,B.ID AS detailId,B.CASH_FORM_ID AS secondCashFormId,B.SOUR_PLACE,B.DES_PLACE,B.NAME,B.SEX,B.COUNTRY,B.BIRTHDAY,B.BIRTHPLACE,B.CERTIFICATE_CATEGORY,B.ID_NUMBER,B.ISSUE_PLACE,B.PLACE_AND_PHONE,B.PHONE,B.CUSTOMS_SIGNATURE,B.FORM_ID  AS cashFormFormId,B.SIGN_DATE,B.FLAG AS detailFlag,B.CASH_FORM_CATEGORY AS cashCaregory,C.ID AS cashformListId , C.CASH_TYPE,C.CURRENCY_VALUE,C.CURRENCY_TYPE,C.ISORNOT,C.OTHER,C.FLAG AS listFlag,C.CASH_FORM_ID AS thirdCashFormId,D.ID AS thirdId,D.OWNER_NAME_LAW,D.OWNER_NAME,D.OWNER_SEX,D.OWNER_ADDRESS,D.CASH_FORM_LIST_ID,D.FLAG AS thirdFlagFROM CUS_CASH_FORM A LEFT JOIN CUS_CASH_FORM_DETAIL B ON B.CASH_FORM_ID = A.ID AND B.FLAG = '1'LEFT JOIN CUS_CASH_LIST C ON C.CASH_FORM_ID = A.ID AND C.FLAG = '1'LEFT JOIN CUS_CASH_FORM_THIRD D ON D.CASH_FORM_LIST_ID = C.ID AND D.FLAG = '1') T WHERE T.FLAG = '1'AND T.STATE != '0'AND T.ID in<foreach item="id" collection="ids" open="(" separator="," close=")">  #{id}</foreach></select>