EJB3 unit testing - part one - dependency injection

You might want to use an embeddable container for this - but why really - cause it's really simple. EJB3 session beans are POJO's and should be tested like POJO's.

However there are some issues in order to get EJB3 unit tests working. One of them are dependency injection.

How does dependency injection work? Take a look at this method using reflection:

* @param targetBean - the bean to inject into
* @param annotationClass - the annotation class representing the injection
* @param objectToInject - the object to inject into targetBean

private void inject(Object targetBean, Class annotationClass, Object objectToInject)
// Scan all (private and public fields) of the bean class
for(Field fld : targetBean.getClass().getDeclaredFields())
// See if the specified annotation is present for the field
// See if the field type is appropriate according to the object that is to be injected
// Make sure that we can set the value of the field (e.g. if it's private)
try {
// Now set the field with the object to inject
fld.set(targetBean, objectToInject);
Logger.getLogger(getClass().getName()).info("Injected "+objectToInject.getClass().getName()+" into "+targetBean.getClass().getName());
} catch (IllegalArgumentException ex) {
Logger.getLogger(getClass().getName()).log(Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
Logger.getLogger(getClass().getName()).log(Level.SEVERE, null, ex);

Now let's see how we can inject the entitymanager and invoke a stateless ejb3 session bean:

// Create session bean instance
MySessionBean mySessionBean = new MySessionBean();
// Inject new entity manager
// Invoke session bean method


Uma said…
Thank you so much, your example helped me a lot.

I was using EJB3Guice to inject the objects to a session bean and it doesn't work.

I was struggling how it make it work and found your example. Thanks a ton!!
Thanks for feedback. I will soon follow up with part two then...
Uma said…
HI Peter,

Will be waiting for your part two..

another question regarding EJB3Unit.

My project uses eclipselink for persistence, and we are testing EJBs using EJB3Unit which uses hibernate for persistence.

So, we have some problems testing the beans.

For example: One of our entities have @Converter, to convert boolean to char or viceversa.

Im not able to test this entity, as hibernate throws constraintviolatedexception.
it cannot convert to boolean to char, and the related table has this field as 'char(1)'.

So, could you pls suggest any other alternative to test this kind of differences (between hibernate & persistence).

Thanks & Regards
I'd prefer testing with the same persistence provider as you use in your application - that is EclipseLink.

My colleague has made EJB3Unit use EclipseLink instead of hibernate - but I don't know the details around this myself.

As for my tests, I haven't used EJB3Unit - but rather implemented those parts of EJB3 needed for my tests (which is mostly only a fraction of a complete EJB3 container).



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