Referring to the artifactId of a maven dependency jar from persistence.xml

Question

We're working with JPA and are trying to stick to standard spec (and avoiding Hibernate-specific features).

We use one project (let's call it X) inside another project (A) as a Maven dependency.

We need JPA to scan project X for Entities as well as scanning project A.

To that end, we've added a line

<jar-file>lib/X-v5-4.0.jar</jar-file>

inside

<persistence-unit>

in persistence.xml. This works fine.

The issue we still have is that we now need to specify the version of project X in not only pom.xml but also in persistence.xml. This is a recipe for problems with deploys in the future.

We've come up with a system using Maven resource filtering:

<jar-file>lib/X-v5-${x-version}.jar</jar-file>

in persistence.xml and

<properties>
  <x-version>4.0</x-version>
</properties>

and ${x-version} in pom.xml.

This works but is still not perfect, as we'll have to remember to update the version number in a non-standard location each time project X gets a new version.

Ideally, we'd like to have a situation where we can adjust version information in the dependency part of pom.xml and changes would propagate to persistence.xml automatically. We'd reduce a lot of possible errors in future deploys this way.

Is this possible?

EDIT (OUR SOLUTION):

we have added a file named jpa.xml. We define an entityManagerFactory, a persistenceAnnotationBeanPostProcessor and a transactionManager in it. The important part here is the entityManagerFactory bean. It has a property "packagesToScan" that allows you to indicate specific packages to scan for entities to put in the persistence context.

A code snippet:

<bean id="entityManagerFactory"
    class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
    <property name="dataSource" ref="jpaDataSource" />
    <property name="loadTimeWeaver">
        <bean
            class="org.springframework.instrument.classloading.InstrumentationLoadTimeWeaver" />
    </property>
    <property name="packagesToScan">
        <list>
            <value>org.com.our.external.library.package1</value>
            <value>org.com.our.external.library.package2</value>
            <value>org.com.our.external.library.package3</value>
        </list>
    </property>
</bean>

I'm sure you see the advantage: as we are referring to these libraries by package signature, we no longer have to worry about jar version numbers.

Answer 1

I have solved it this way:

in persistence.xml substitute the whole <jar-file> tag, i.e.

<persistence-unit name="PersistenceUnit">
    ...
    <!-- here is where the jar file is supposed to go -->
    ${importjarfile}
    ...
</persistence-unit>

Finally, set your properties like this:

<properties>
    <x-version>4.0</x-version>
    <importjarfile><![CDATA[<jar-file>lib/X-v5-${x-version}.jar</jar-file>]]></importjarfile>
</properties>

In this way Eclipse won't see the jar-file tag and won't complain.

My solution was actually a little bit cleaner since I was using a .properties file so I didn't have to use CDATA, I hope it still works.

My solution:

importjarfile = <jar-file>lib/X-v5-${x-version}.jar</jar-file>