JPA - 带有鉴别器插入的单表继承但无法检索正确的对象

时间：2011-07-22 20:27:01

标签： hibernate jpa-2.0

我有两个表'Task'和'Contents'。我使用带有鉴别器的单表继承将两个实体（PrimaryContent，AttachmentContent）映射到'Contents'表。我有一个父实体Task，它与两个内容实体保持一对一的关系。我可以插入Task实体及其PrimaryContents和AttachmentContents的集合。我看到hibernate在每种类型的鉴别器列中插入了正确的值。问题是当我查询Task实体及其内容实体的集合时，hibernate会抛出异常 - ＆gt;引起：org.hibernate.WrongClassException：id为10024的对象不是指定的子类：com.xxx.PrimaryContent（加载的对象是类com.xxx.AttachmentContent错误的类）。看起来似乎没有在hibernate生成的select语句中使用鉴别器列。

在这里，您可以看到任务实体根据其pk正确查询：

Hibernate: select * from ( select communicat0_.COMM_TASK_ID as COMM1_92_,    communicat0_.BUSINESS_CONTEXT as BUSINESS2_92_, communicat0_.BUSINESS_ID as BUSINESS3_92_, communicat0_.CREATE_DT as CREATE4_92_, communicat0_.STAT_RSN_CD as STAT5_92_, communicat0_.SENDERS_EMAIL_ID as SENDERS6_92_, communicat0_.SENDERS_NM as SENDERS7_92_, communicat0_.STATUS_DT as STATUS8_92_, communicat0_.STATUS_CD as STATUS9_92_, communicat0_.SOURCE_SYSTEM as SOURCE10_92_, communicat0_.TRANSACTION_REFERENCE_ID as TRANSAC11_92_, communicat0_.UPDATE_DT as UPDATE12_92_, communicat0_.USER_ID as USER13_92_  from COMMPREF.COMMUNICATION_TASKS communicat0_ where communicat0_.COMM_TASK_ID=10029 ) where rownum <= ?

以下是其中一个集合（PrimaryContent实体）的查询：

Hibernate: select primarycon0_.COMM_TASK_ID as COMM24_92_1_, primarycon0_.COMM_CONTENT_ID as COMM2_1_, primarycon0_.COMM_CONTENT_ID as COMM2_93_0_, primarycon0_.ARCHIVE_DT as ARCHIVE3_93_0_, primarycon0_.ARCHIVE_REF_ID as ARCHIVE4_93_0_, primarycon0_.FILE_NAME as FILE5_93_0_, primarycon0_.FILE_PATH as FILE6_93_0_, primarycon0_.FORMAT_TYPE_CD as FORMAT7_93_0_, primarycon0_.CONTENT_NM as CONTENT8_93_0_, primarycon0_.PAGE_COUNT as PAGE9_93_0_, primarycon0_.COMM_CAT_CD as COMM10_93_0_, primarycon0_.EDIT_YN as EDIT11_93_0_, primarycon0_.FILE_LOCKED_BY as FILE12_93_0_, primarycon0_.FILE_LOCKED_DT as FILE13_93_0_, primarycon0_.PREVIEW_YN as PREVIEW14_93_0_, primarycon0_.STAT_RSN_CD as STAT15_93_0_, primarycon0_.STATUS_DT as STATUS16_93_0_, primarycon0_.STATUS_CD as STATUS17_93_0_, primarycon0_.COMM_TASK_ID as COMM24_93_0_, primarycon0_.TEMPLATE_ID as TEMPLATE18_93_0_, primarycon0_.TEMPLATE_NM as TEMPLATE19_93_0_, primarycon0_.TEMPLATE_VERSION as TEMPLATE20_93_0_, primarycon0_.USER_ID as USER21_93_0_ from COMMPREF.COMM_CONTENTS primarycon0_ where primarycon0_.COMM_TASK_ID=?

如您所见，where子句中没有使用鉴别器列。这只是我的实体映射的问题吗？我在下面列出了表格和orm映射：

表：

Tasks:
+id (pk) 
+other fields

contents:
+id (pk)
+task_id (fk)
+primary_content_id (fk) <-- the self association 
+segment_type <-- my discriminator column

任务：

<entity-mappings xmlns="http://java.sun.com/xml/ns/persistence/orm"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/persistence/orm
 http://java.sun.com/xml/ns/persistence/orm_2_0.xsd"
    version="2.0">
    <description></description>
    <package></package>
    <schema></schema>
    <access>FIELD</access>
    <entity class="com.xxx.CommunicationTask"
        access="FIELD" metadata-complete="true">
        <table name="COMMUNICATION_TASKS" />
        <attributes>
            <id name="id">
                <column name="COMM_TASK_ID" />
                <generated-value strategy="SEQUENCE" generator="TASK_SEQ"  />
                <sequence-generator name="TASK_SEQ"
                    sequence-name="COMMPREF.TASK_SEQ" allocation-size="1" />
            </id>
            <one-to-many name="attachmentContents" target-   entity="com.xxx.AttachmentContent" 
                mapped-by="task" orphan-removal="true">
                <cascade>
                    <cascade-all />
                </cascade>
            </one-to-many>
        <one-to-many name="primaryContents" target-entity="com.xxx.PrimaryContent" 
                mapped-by="task" orphan-removal="true">
                <cascade>
                    <cascade-all />
                </cascade>
        </one-to-many>
        </attributes>
    </entity>
  </entity-mappings>

内容基础：

<entity-mappings xmlns="http://java.sun.com/xml/ns/persistence/orm"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/persistence/orm
  http://java.sun.com/xml/ns/persistence/orm_2_0.xsd"
    version="2.0">
    <description></description>
    <package></package>
    <schema></schema>
    <access>FIELD</access>
    <entity name="CommunicationContent" class="com.xxx.CommunicationContent"  access="FIELD" metadata-complete="true">
    <table name="COMM_CONTENTS"/> 
    <discriminator-column name="COMM_SGMNT_TYPE_CD"/>
    <attributes>
        <id name="id">
            <column name="COMM_CONTENT_ID"/>
            <generated-value strategy="SEQUENCE" generator="CONTENT_SEQ"/>
            <sequence-generator name="CONTENT_SEQ" sequence-name="COMMPREF.CONTENT_SEQ"     allocation-size="1"/>
        </id>
    </attributes>
 </entity>
 </entity-mappings>

主要内容：

<?xml version="1.0" encoding="UTF-8"?>
 <entity-mappings xmlns="http://java.sun.com/xml/ns/persistence/orm"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/persistence/orm
   http://java.sun.com/xml/ns/persistence/orm_2_0.xsd"
    version="2.0">
    <description></description>
    <package></package>
    <schema></schema>
    <access>FIELD</access>
    <entity name="PrimaryContent" class="com.xxx.PrimaryContent"
        access="FIELD" metadata-complete="true">
        <discriminator-value>P</discriminator-value>
        <attributes>
            <many-to-one name="task" fetch="LAZY">
                <join-column name="COMM_TASK_ID" nullable="false"/>
            </many-to-one>
        </attributes>
    </entity>
 </entity-mappings>

附件内容：

<entity-mappings xmlns="http://java.sun.com/xml/ns/persistence/orm"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/persistence/orm
   http://java.sun.com/xml/ns/persistence/orm_2_0.xsd"
    version="2.0">
    <description></description>
    <package></package>
    <schema></schema>
    <access>FIELD</access>
    <entity name="AttachmentContent" class="com.xxx.AttachmentContent"
        access="FIELD" metadata-complete="true">
        <discriminator-value>A</discriminator-value>
        <attributes>
            <many-to-one name="task" fetch="LAZY">
                <join-column name="COMM_TASK_ID" nullable="false"/>
            </many-to-one>
        </attributes>
    </entity>
 </entity-mappings>

1 个答案:

答案 0 :(得分：0)

在你的orm.xml中，你的鉴别器列为：

<discriminator-column name="COMM_SGMNT_TYPE_CD"/>

但是在您的表定义中，您将其称为segment_type

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