JPA - multiple jars defining @Entity objects

Question

We are developing a web application with Spring, Hibernate and Maven in a very modular fashion. There are core projects defining data access and view specific stuff, then th

Answer 1

We use a similar module layout, but we place the persistence context in the war-part of our application and inject the entitymanager into the DAOs of the modules. Except for unit testing, the modules don't have a PU. We did this because we were afraid, that a transaction spanning multiple modules could cause trouble.

In the DAO

@PersistenceContext
private EntityManager em;

In the persistance.xml you need to enlist all entities with the elements.

<persistence-unit name="myPU">
    <class>com.Entity1</class>      
<class>com.Entity2</class>

etc.

Answer 2

Well, we' re having a similar problem on our development cycle. If your referencing entities are in another -ejb.jar file (that's our case) you can bind these entities with

<jar-file>relativePathToYourJar/dependent-entities-ejb.jar</jar-file>

tag. Notice that you should also include a persistence.xml under dependent-entities-ejb.jar's META-INF folder. Further information could be found here.

Answer 3

Since the question seems to still get attention, I'll post our latest solution to the problem.

We are now auto-scanning all packages instead of using persistence.xml files anywhere.

In our datasource.xml we added the line

<property name="packagesToScan" value="our.basepackage" />

Almost complete datasource.xml:

<!-- Bean definition here -->

<bean id="ourDataSource"
    class="org.springframework.jdbc.datasource.DriverManagerDataSource">
    <property name="driverClassName" value="com.mysql.jdbc.Driver" />
            <!-- define connection properties -->       
</bean>


<bean id="entityManagerFactory"
    class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
    <property name="dataSource" ref="ourDataSource" />
    <property name="packagesToScan" value="our.basepackage" />
    <property name="jpaVendorAdapter">
        <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
            <property name="showSql" value="false" />
            <property name="generateDdl" value="true" />
            <property name="databasePlatform" value="org.hibernate.dialect.MySQL5InnoDBDialect" />
        </bean>
    </property>

</bean>

<tx:annotation-driven transaction-manager="transactionManager" />
<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager" />

Answer 4

I've made a solution like tugcem, but because I am using Maven I would hate to have the jar version numbers in my persistence.xml. The solution I came up with is described here: JPA 2.0: Adding entity classes to PersistenceUnit *from different jar* automatically

Answer 5

The classes will be in the class loader.

This so answer Scanning Java annotations at runtime.

Is that what you want? To scan for @Entity annotated and add them to a PersistenceUnit?

Regards.