Registering entity types with OpenJPA programmatically

I’ve just started work on an OpenJPA objectstore for Isis. In the normal scheme of things, one would register the entity types within the persistence.xml file. However, Isis is a framework that builds its own metamodel, and can figure out for itself which classes constitute entities. I therefore didn’t want to have to force the developer to repeat themselves, so the puzzle became how to register the entity types programmatically within the Isis code.

It turns out to be pretty simple, if a little ugly. OpenJPA allows implementations of certain key components to be defined programmatically; these are specified in a properties map that is then passed through to javax.persistence.Persistence.createEntityManager(null, props). But it also supports a syntax that can be used to initialize those components through setter injection.

In my case the component of interest is the openjpa.MetaDataFactory. At one point I thought I’d be writing my own implementation; but it turns out that the standard implementation does what I need, because it allows the types to be injected through its setTypes(List<String>) mutator. The list of strings is passed into that property as a ;-delimited list.

So, here’s what I’ve ended up with:

final Map<String, String> props = Maps.newHashMap();

final String typeList = entityTypeList();
  "org.apache.openjpa.persistence.jdbc.PersistenceMappingFactory(types=" + typeList + ")");

// ... then add in regular properties such as 
// openjpa.ConnectionURL, openjpa.ConnectionDriverName etc...
entityManagerFactory = Persistence.createEntityManagerFactory(null, props);

where entityTypeList() in my case looks something like:

private String entityTypeList() {
    final StringBuilder buf = new StringBuilder();
    // loop thru Isis' metamodel looking for types that have been annotated using @Entity
    final Collection<ObjectSpecification> allSpecifications = 
    for(ObjectSpecification objSpec: allSpecifications) {
        if(objSpec.containsFacet(JpaEntityFacet.class)) {
            final String fqcn = objSpec.getFullIdentifier();
    final String typeList = buf.toString();
    return typeList;

Comments welcome, as ever

Reference: Registering entity types with OpenJPA programmatically from our JCG partner Dan Haywood at the Dan Haywood blog blog.

Do you want to know how to develop your skillset to become a Java Rockstar?

Subscribe to our newsletter to start Rocking right now!

To get you started we give you two of our best selling eBooks for FREE!

JPA Mini Book

Learn how to leverage the power of JPA in order to create robust and flexible Java applications. With this Mini Book, you will get introduced to JPA and smoothly transition to more advanced concepts.

JVM Troubleshooting Guide

The Java virtual machine is really the foundation of any Java EE platform. Learn how to master it with this advanced guide!

Given email address is already subscribed, thank you!
Oops. Something went wrong. Please try again later.
Please provide a valid email address.
Thank you, your sign-up request was successful! Please check your e-mail inbox.
Please complete the CAPTCHA.
Please fill in the required fields.

Leave a Reply

7 + = ten

Java Code Geeks and all content copyright © 2010-2014, Exelixis Media Ltd | Terms of Use | Privacy Policy | Contact
All trademarks and registered trademarks appearing on Java Code Geeks are the property of their respective owners.
Java is a trademark or registered trademark of Oracle Corporation in the United States and other countries.
Java Code Geeks is not connected to Oracle Corporation and is not sponsored by Oracle Corporation.
Do you want to know how to develop your skillset and become a ...
Java Rockstar?

Subscribe to our newsletter to start Rocking right now!

To get you started we give you two of our best selling eBooks for FREE!

Get ready to Rock!
You can download the complementary eBooks using the links below: