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POJPA Inheritance
 

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    <p>Hi I'm new to JPA and I'm having trouble understanding how it handles inheritance.</p> <p>I have a specific problem I need solved without changing the DB scheme, but if you can't find a solution I would appreciate solution suggestions with a different DB scheme (Hibernate/TopLink solutions welcome).</p> <p>If I was unclear or you need more information, please tell me so. Thanks in advance!</p> <p>I have this database:</p> <pre><code>TABLE Fruit Id Varchar (10) Primary Key size Varchar (10) fruit_type Varchar(10) TABLE Apple Id Varchar (10) Primary Key Foreign Key references Fruit.Id Apple_Property Varchar(10) </code></pre> <p>So far my entities look like this :</p> <pre><code>@Entity @Inheritance(strategy=InheritanceType.JOINED) @DiscriminatorColumn(name="fruit_type", discriminatorType=DiscriminatorType.Char) @DiscriminatorValue(value="fruit") public class Fruit implements Serializable { @Id protected String Id; protected String size; } @Entity @DiscriminatorValue(value="apple") //@PrimaryKeyJoinColumn(name="Id" , referencedColumnName="Id") public class Apple extends Fruit implements Serializable { private String Apple_Property; } </code></pre> <p>Currently I am able to persist Fruit objects without a problem.. Apple objects persist only when their Fruit object hasn't been persisted yet.</p> <p>If I try to persist an apple object with an already persisted Fruit object :</p> <pre><code>Fruit fruit1 = new Fruit("1", "Small"); Apple apple1 = new Apple(fruit1, "red"); provider.create(fruit1); provider.create(apple1); </code></pre> <p>I will get an error since JPA tries to create a new row on Fruit table with Id="1" which already exists.</p> <p>..</p>
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