如何将抽象类的ORM编写为超类无注释

问题描述

我有一个名为 User.java 的类，它具有活动列表。 Activity.java 是由 Dance.java 和 Drawing.java扩展的抽象类

    public class User {
        private UserKey userKey; // PK (UserKey is another embeddable class and has a string userId)
        private List<Activity> activities;
        
        //some more fields and getter setters
    }

    public abstract class Activity {
        // has nothing. I can add ID field if needed.
    }

    public class Dance extends Activity {
     private DanceKey danceKey; // PK. DanceKey is another embeddable class and has a string danceId.
     private String danceName;
     // some more fields and getter setters
    }

    public class Drawing extends Activity {
     private DrawingKey drawingKey; // PK. DrawingKey is another embeddable class and has a string drawingId.
     private String drawingName;
     // some more fields and getter setters
    }

以下是orm文件：

user.orm.xml

    <?xml version="1.0" encoding="UTF-8"?>
    <entity-mappings version="2.5"
        xmlns="http://www.eclipse.org/eclipselink/xsds/persistence/orm"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://www.eclipse.org/eclipselink/xsds/persistence/orm http://www.eclipse.org/eclipselink/xsds/eclipselink_orm_2_5.xsd">
        <entity name="User" class="com.app001.demo.User">
            <table name="USER" />
            <attributes>
                 <embedded-id attribute-type="com.app001.demo.UserKey" name="userKey">
                     <attribute-override name="key">
                        <column name="USER_ID"/>
                     </attribute-override>
                 </embedded-id>
                
                <!-- what do i put here for list of activities-->
                 
            </attributes>
        </entity>
    </entity-mappings>

dance.orm.xml

    <?xml version="1.0" encoding="UTF-8"?>
    <entity-mappings version="2.5"
        xmlns="http://www.eclipse.org/eclipselink/xsds/persistence/orm"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://www.eclipse.org/eclipselink/xsds/persistence/orm http://www.eclipse.org/eclipselink/xsds/eclipselink_orm_2_5.xsd">
        <entity name="Dance" class="com.app001.demo.Dance">
            <table name="DANCE" />
            <attributes>
                 <embedded-id attribute-type="com.app001.demo.DanceKey" name="danceKey">
                     <attribute-override name="key">
                        <column name="DANCE_ID"/>
                     </attribute-override>
                 </embedded-id>
                 <basic attribute-type="java.lang.String" name="danceName">
                            <column name="DANCE_NAME"/>
                 </basic>
            </attributes>
        </entity>
    </entity-mappings>

drawing.orm.xml

    <?xml version="1.0" encoding="UTF-8"?>
    <entity-mappings version="2.5"
        xmlns="http://www.eclipse.org/eclipselink/xsds/persistence/orm"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://www.eclipse.org/eclipselink/xsds/persistence/orm http://www.eclipse.org/eclipselink/xsds/eclipselink_orm_2_5.xsd">
        <entity name="Drawing" class="com.app001.demo.Drawing">
            <table name="DRAWING" />
            <attributes>
                 <embedded-id attribute-type="com.app001.demo.DrawingKey" name="drawingKey">
                     <attribute-override name="key">
                        <column name="DRAWING_ID"/>
                     </attribute-override>
                 </embedded-id>
                 <basic attribute-type="java.lang.String" name="drawingName">
                            <column name="DRAWING_NAME"/>
                 </basic>
            </attributes>
        </entity>
    </entity-mappings>

activity.orm.xml

    <?xml version="1.0" encoding="UTF-8"?>
    <entity-mappings version="2.5"
        xmlns="http://www.eclipse.org/eclipselink/xsds/persistence/orm"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://www.eclipse.org/eclipselink/xsds/persistence/orm http://www.eclipse.org/eclipselink/xsds/eclipselink_orm_2_5.xsd">
        
        <!-- what do i put here for activity-->

我尝试了以下方法：

1. 在activity.orm.xml中，如果我将Activity.java设为<mapped-superclass>，则此方法不起作用，因为不允许我与<inheritance-strategy>一起输入任何<mapped-superclass>
2. 在activity.orm.xml中，如果我将Activity.java标记为<entity>，将<inheritance_strategy>标记为 TABLE_PER_CLASS 或 JOINED 我收到以下错误： 在同步期间，通过未标记为层叠PERSIST的关系找到了一个新对象

请让我知道如何为我的案例为activity.orm.xml编写ORM。 注意 ，我不能过多地更改Java代码。如果需要，我可以在Activity.java中添加一个ID。

解决方法

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