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Is Eclipse Dynamic Persistence support SINGLE_TABLE Inheritance strategy ? [message #1720819]

Thu, 21 January 2016 09:14

gaurav Gupta

Messages: 1
Registered: January 2016

Junior Member

Is Eclipse Dynamic Persistence support SINGLE_TABLE Inheritance strategy ?

I have tried dynamic persistence for both JOINED and TABLE_PER_CLASS , this is working fine but not working for SINGLE_TABLE .

For example :

<?xml version="1.0" encoding="UTF-8"?>
<entity-mappings version="2.1"     xmlns="....sample xml.....">
    <package>example.jpa.dynamic.model.employee</package>
    <entity class="Node" access="VIRTUAL" >
            <inheritance strategy="SINGLE_TABLE" />
        <attributes>
            <id name="id" attribute-type="Integer"/>
            <basic name="name" attribute-type="String" />
        </attributes>
    </entity>
    <entity class="Folder" access="VIRTUAL" parent-class="Node">
        <attributes>
            <basic name="iconColor" attribute-type="String" />
        </attributes>
    </entity>
    <entity class="File" access="VIRTUAL" parent-class="Node">
        <attributes>
            <basic name="extension" attribute-type="String" />
        </attributes>
    </entity>
</entity-mappings>

In this case scenario only single table Node is created with 3 column ID , NAME , DTYPE .

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Re: Is Eclipse Dynamic Persistence support SINGLE_TABLE Inheritance strategy ? [message #1721193 is a reply to message #1720819]

Mon, 25 January 2016 15:32

Chris Delahunt

Messages: 1389
Registered: July 2009

Senior Member

Dynamic persistence works with any inheritance type. The issue you seem to be encountering is with DDL generation, and since a table can only be created once, it can't be created later on with extended attributes as you add in additional subclasses - they need to all be created upfront. You can try using the "create-or-extend-tables" "eclipselink.ddl-generation" option, but as DDL generation is not meant for production, what is instead recommended is you add generic attributes to your table upfront and then assign them when creating dynamic entities.

Best Regards,
Chris

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