Tomcat, TomEE or GlassFish? I like the simple life. But getting to the simple always seems to take so long. And with enterprise java sometimes even longer than that… I was experimenting with Java EE 6 RESTful Web Services and Entity beans generated with NetBeans when I thought it would be good to test how easy it would be run this app on Tomcat, TomEE and GlassFish. Well, with Tomcat I would have to build my own Tomcat based Java EE 6 server (again). To be honest I couldn’t be bothered and the guys at TomEE had already done that. So it was between GlassFish, the reference EE server, and TomEE.
Running one of the sample NetBean apps, Customer Database on Spring, on GlassFish is as easy as you might expect, but porting that to TomEE was more difficult than I expected… With TomEE there is a choice to be made from the 3 versions currently available; standard, web services and enterprise options (not the official names). I really only wanted the web service version (Java EE 6 Certified JAX-RS) for its RESTful web services but as I wasn’t sure if that contained everything that I would need I went with the enterprise version (TomEE 1.5.1 Plus) which has the most supported APIs.
With the TomEE version choice made I started googling for what seemed like days for documentation, help, examples, anything that would help me to configure an app on TomEE, an app that took minutes to write in NetBeans and run on GlassFish. Finally stumbling across this I was able to piece together what was required to get things working on TomEE.
A resources.xml file needs to be in the WEB-INF/classes/META-INF folder to define a data source, e.g. this example defines a Derby data source.
I also had to update the persistence.xml file to use the EclipseLink JPA provider as I just couldn’t get the default TomEE JPA provider (OpenJPA) to work…
TomEE 1.5.1 doesn’t like Spring injecting an EntityManager, as documented here. So I removed that from the Spring config, instead relying on the GlassFish managed entity manager. No big deal there, and not a big deal either to remove the lines of code that were closing the entity manager, as that isn’t allowed with a container manager entity manager.
All in all it wasn’t too hard to prove that a simple Java EE 6 app can be ported from GlassFish to TomEE.