How do I depend on hibernate annotated mappings from a separate project?

Question

I am trying to work out how to do the mappings for two different projects that share some entities. Since they share only a limited subset of mappings, my first idea was to separate these mappings out into a separate jar. I'm using hibernate annotations to do the mappings (so they're in the class files, not separate XML).

Both project A and project B depend on this mappings project, which contains only a couple of hibernate mappings. Project A has no mappings of its own but project B does. Whatever I do this always seems to cause problems since if I don't configure a persistence unit for the mappings project, the mappings are never picked up on. Likewise for project B. If I do configure a persistence unit in the mappings project, project A works, but running a query in project B just gives me (Mapping happens to be the name of the class):

java.lang.IllegalArgumentException: org.hibernate.hql.ast.QuerySyntaxException: Mapping is not mapped

I believe this is caused by project B having its own persistence unit, and obviously the two are not being merged. I don't really want them to either, I'd prefer to only configure one in project A/B and not the jar they depend on. So is there a way to tell hibernate to scan and map the annotations in a dependency jar and add them to the current persistence unit?

Answer 1

I do not know whether you use Spring but i use Spring capabilities To get this behavior by using packagesToScan property among with mappingLocations property as follows

<bean id="sessionFactory" class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean">
    <property name="dataSource" ref="dataSource"/>
    <property name="mappingLocations">
        <util:list>
            <value>classpath:br/com/ar/model/repository/hql.ar.hbm.xml</value>
            <value>classpath:br/com/br/model/repository/hql.br.hbm.xml</value>
            <value>classpath:br/com/cr/model/repository/hql.cr.hbm.xml</value>
        </util:list>
    </property>
    <property name="packagesToScan">
        <util:list>
            <value>br.com.ar.model.domain</value>
            <value>br.com.br.model.domain</value>
            <value>br.com.cr.model.domain</value>
        </util:list>
    </property>
    <property name="hibernateProperties">
        <props>
            <prop key="hibernate.dialect">org.hibernate.dialect.Oracle9Dialect</prop>
            <prop key="hibernate.connection.charSet">UTF-8</prop>
            <prop key="hibernate.show_sql">true</prop>
            <prop key="hibernate.format_sql">true</prop>
            <prop key="hibernate.validator.autoregister_listeners">false</prop>
        </props>
    </property>
</bean>

I hope It can be useful

UPDATE

According To JPA specification

The set of managed persistence classes that are managed by a persistence unit is defined by using one or more of the following:

• One or more object/relational mapping XML files
• One or more jar files that will be searched for classes
• An explicit list of the classes
• The annotated managed persistence classes contained in the root of the persistence unit (unless the exclude-unlisted-classes element is specified)

As follows

<persistence>
    <persistence-unit name="titan">
        <!--Explicity list of classes-->
        <class>br.com.ar.model.domain.A</class>
        <class>br.com.ar.model.domain.B</class>
        <!--Set up any jar file by using jar-file element-->
        <!--Its value is a path relative to the JAR file that contains persistence.xml-->
        <jar-file>../lib/customer.jar</jar-file>
        <!--ORM mapping file-->
        <!--It may be present anywhere on the class path-->
        <mapping-file>mapping.xml</mapping-file>
        <properties>
            Properties goes here
        </properties>
    </persistence-unit>
</persistence>