WildFly RestEasy Version confusion

Question

I want to build a REST API using RestEasy. The generated file should be deployed in a WildFly application server.

I face the issue described in the following SO-question: AsynchronousDispatcher error

The marked solution tells me, to set the dependency to "provided". Which as far as I understand means, that the library is not included in my war file but taken directly from the app-server...

Isn't that just wrong?

My idea would be to build a self-containing war file which contains all the needed libraries in the version I need.

When provided from the app-server I do get the currently available version from there. I have not really a clue about the version... when someone has the idea to update the RestEasy library on the server, it might break my app.

I'm not sure whether I missed something or did something completely wrong?

Answer 1

One of the big advantages to Java EE is developing towards the API and not having to worry about the implementation. Java EE containers provide the API's and implementations for the API's. If you include implementation dependencies one of two things is likely to happen.

1. You're dependencies will be ignored making it pointless to include them in your deployment.

2. You'll get conflicts between the dependencies you included vs what the server is expecting. This could be things like:

   • ClassCastException because it's finding two of the same class on the class path.
   • MethodNotFoundException because there is a version mismatch
   • Various other issues with conflcts

Developing towards the API instead of the implementation also allows you to easily switch between Java EE compliant containers with no to minimal changes to your deployment. The API's are generally backwards compatible as well making version upgrades not as big of an issue.

If you want to use a fat WAR (including implementations) instead of a skinny WAR (not including the implementations) then a servlet container is probably a better solution. WildFly does have a servlet only download. I'd encourage you though to trust container to do the right thing with the implementation dependencies :). Usually the only time there is an issue with upgrading is if you're upgrading Java EE versions. Even then it's usually pretty safe.