I'm in a difficult position: We have a 3rd party enterprise system that exposes a Java-based API. However, we are a 100% .Net oriented development team. Essentially, I need to wrap the Java API with something that C# code can call.
Web services would be great, but the only Java application server supported on our infrastructure is WebSphere 6.1. This means the ancient (and deprecated) JAX-RPC web service framework is the only way for us to expose web services. Just getting a simple proof-of-concept working here has been a nightmare (because of Java inexperience, WebSphere being awful, JAX-RPC being clunky, and lots of JAR hell).
The new JAX-WS 2.0 web service framework in JAVA EE 5 looks great-- is there any way to run this without an entire Java application server? For example, in .Net's WCF (Windows Communication Framework), you can host services pretty much anywhere you want (in-process, Windows Service, IIS 6/7 etc).
What is the most lightweight way to wrap this library with some web services?
I ended up finding a solution that was far easier than any of the above. We created some simple classes (like the doPing() method in @Thorbjørn Ravn Andersen's answer) with the @javax.jws.WebService and @javax.jws.WebMethod annotations, then deployed them using:
string url = "http://localhost:8282/MyService"
MyService serviceInstance = new MyService();
Endpoint svc = Endpoint.publish(url, serviceInstance);
I was then able to point Visual Studio at http://localhost:8282/MyService?wsdl and generate a client. Easy as pie.
We have run a lot of requests through this service over a large span of time and have not noticed any problems. We wrapped this with the Java Service Wrapper so that it comes back up across reboots/JVM crashes, etc. A poor man's application server.
I hope this might help any other .NET developer looking to interoperate with Java without having to remap your brain to do it.