I have developed a webservice in Java that runs as a servlet on a tomcat, parameters for the application are given to the servlet via the get request (e.g. servlet?method=search&query=searchterm123), the servlet recognizes if the method and the query are defined and in the case of an error gives back a string that is manually wrapped in xml code that I hardcoded via this.writer.println(answer);. If the method is right a new class is instantiated which does the search and then gives back an object which XStream converts into XML for me which I then again send back to the client with println wrapped into my xml overhead that is again hard coded String answer ="<?xml version=\"1.0\" encoding=\"utf-8\" ?>\n".
Obviously this works and also very efficiently but this is far from elegant. I have looked into Apache CXF very briefly and also into things like RESTlet or JBOSS RestEasy, the latter two I found to much for my demands. Every tutorial I find on CXF always includes Spring and Maven which then overwhelms me a little. Do you have suggestions how I should turn my dirty hack into a pretty application?
I think using a JAX-RS framework (as CXF and Resteasy, but also Jersey) is the way to go in your case. Regarding serializing to XML, maybe have a look at JAXB (as included in Jersey too for instance). It should help automatically serialize any entity structure.
Regarding the complexity of such application: it should always depend on what infrastructure you use. If its just a simple Java EE server, its possibly best to use the implementation of that vendor (Jersey for Glassfish, Resteasy for JBoss). Otherwise, just use the build system you are familiar and comfortable with. You can easily replace the Maven dependencies with Ant and Ivy for example.