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POseparating JPA entities from Hibernate-specific tweaks
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copied!<p>I have the following "root" entity (hibernate-specific parts commented out):</p> <pre><code>@Entity //@GenericGenerator(name="system-uuid",strategy="org.hibernate.id.UUIDGenerator") public class Node extends PersistentEntity { private UUID id; private String name; private String displayName; @Id @GeneratedValue //@GeneratedValue(generator="system-uuid") //instead of above line //@Type(type = "pg-uuid") public UUID getId() { return id; } public String getName() { return name; } public String getDisplayName() { return displayName; } //stuff omitted } </code></pre> <p>this is part of a persistence context deployed on JBoss AS 6 (hibernate 3.6) using PostgreSQL 9 for the database (using the latest JDBC4 driver). PostgreSQL has its own uuid column type, which requires some hibernate-specific mappings to use properly (commented out in the above code) - otherwise hibernate will try to map the UUID field to BINARY, then the PostgreSQL dialect does not support BINARY (apparently because postgre has 2 ways of storing binary and hibernate devs dont like it) and the whole thing explodes.</p> <p>uncommenting the lines above produces working code, but it forces me to have a compile-time dependency on hibernate - which i'd rather avoid.</p> <p>attempting to add an hbm.xml file into the mix and referencing it from the persistence.xml does not merge data from the file and annotations, but simply ignores the annotations:</p> <pre><code><?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"> <hibernate-mapping package="package"> <class name="Node"> <id name="id" type="pg-uuid"> <generator class="org.hibernate.id.UUIDGenerator"/> </id> </class> </hibernate-mapping> </code></pre> <p>i can "fluff" this file up by adding the extra 2 properties, but even if i do that (at which point the Node class works), adding any extra entities, like:</p> <pre><code>@Entity public class Host extends Node { //fields, getters, fluff }</code></pre> <p>i get the following exception:</p> <pre><code>org.hibernate.DuplicateMappingException: Duplicate class/entity mapping Node</code></pre> <p>since hibernate "finds" Node twice. is there any elegant way around this? ideally, Node is the only class for which i'll need hibernate-specific properties, and it will be the root of a large hierarchy of classes. i'd like to avoid either compile-time dependencies on hibernate or mapping everything completely in hbm.xml. for completeness' sake, here's the persistence.xml file im using:</p> <pre><code><?xml version="1.0" encoding="UTF-8"?> <persistence xmlns="http://java.sun.com/xml/ns/persistence" version="2.0"> <persistence-unit name="myPU" transaction-type="JTA"> <jta-data-source>java:/my-postgresql-DS</jta-data-source> <mapping-file>META-INF/hbm.xml</mapping-file>   <validation-mode>AUTO</validation-mode> <properties> <property name="hibernate.hbm2ddl.auto" value="create-drop"/> </properties> </persistence-unit> </persistence> </code></pre>

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