ibatis的含有外键的OR映射

对于有外键的主表映射，在查询返回结果时要使用resultmap进行映射，并在propety里使用select属性进行子查询。

public class PetitionLetter {
	private int id;                              
	private String identifier;                   
	private Reporter reporter;         //外键，数据库里是int类型          
	private LetterInformation letterInformation;   //外键，数据库里是int类型
	private Supervision supervision;     //外键，数据库里是int类型    
	private ProcessFlow processFlow;     //外键，数据库里是int类型
}

<sqlMap namespace="PetitionLetter">
  <typeAlias alias="PetitionLetter" type="com.cs.jfb.input.model.PetitionLetter"/>
  <typeAlias alias="ProcessFlow" type="com.cs.jfb.process.model.ProcessFlow"/>
  <typeAlias alias="Reporter" type="com.cs.jfb.input.model.Reporter"/>
  <typeAlias alias="LetterInformation" type="com.cs.jfb.input.model.LetterInformation"/>
  <typeAlias alias="Supervision" type="com.cs.jfb.supervision.model.Supervision"/>
 
  <resultMap id="PetitionLetterResult" class="PetitionLetter">
    <result property="id" column="id"/>
    <result property="identifier" column="identifier"/>
    <result property="reporter" column="reporter" select="selectReporter"/>
    <result property="letterInformation" column="letterInformation" select="selectLetterInformation"/>
    <result property="supervision" column="supervision" select="selectSupervision"/>
    <result property="processFlow" column="processFlow" select="selectProcessFlow"/>
  </resultMap>

  <!-- Select with no parameters using the result map for Account class. -->
  <select id="selectAllPetitionLetter" resultMap="PetitionLetterResult">
    select * from t_petitionletter
  </select>
  
  <select id="selectProcessFlow" resultClass="ProcessFlow" parameterClass="int">
  	select * from t_processflow where id = #id#
  </select>
  
  <select id="selectReporter" resultClass="Reporter" parameterClass="int">
  	select * from t_reporter where id = #id#
  </select>
  
  <select id="selectLetterInformation" resultClass="LetterInformation" parameterClass="int">
  	select * from t_letterinformation where id = #id#
  </select>
  
  <select id="selectSupervision" resultClass="Supervision" parameterClass="int">
  	select * from t_supervision where id = #id#
  </select>
  
  <select id="selectPetitonLetterById" parameterClass="int" resultMap="PetitionLetterResult">
  	select * from t_petitionletter where id = #id#
  </select>
</sqlMap>