the problem was probably caused by some (transitive) dependency conflict in my own project. I had way too many (inherited) dependencies for my small desktop-app project and after I removed them the error was gone.
I now have another error ;-).
8-jun-2011 14:34:03 com.sun.jersey.api.core.PackagesResourceConfig init
INFO: Scanning for root resource and provider classes in the packages:
org.jaxrx.resource
8-jun-2011 14:34:04 com.sun.jersey.api.core.ScanningResourceConfig logClasses
INFO: Root resource classes found:
class org.jaxrx.resource.JaxRxResource
class org.jaxrx.resource.XMLResource
8-jun-2011 14:34:04 com.sun.jersey.api.core.ScanningResourceConfig init
INFO: No provider classes found.
8-jun-2011 14:34:04 com.sun.jersey.server.impl.application.WebApplicationImpl _initiate
INFO: Initiating Jersey application, version 'Jersey: 1.6 03/25/2011 01:14 PM'
8-jun-2011 14:34:04 com.sun.jersey.spi.container.ContainerResponse write
SEVERE: A message body writer for Java class org.basex.api.jaxrx.BXJaxRx$2, and Java type class org.basex.api.jaxrx.BXJaxRx$2, and MIME media type text/xml; omit-xml-declaration=no was not found
8-jun-2011 14:34:04 com.sun.jersey.spi.container.ContainerResponse write
SEVERE: The registered message body writers compatible with the MIME media type are:
*/* ->
com.sun.jersey.server.impl.template.ViewableMessageBodyWriter
8-jun-2011 14:34:04 com.sun.jersey.spi.container.ContainerResponse logException
SEVERE: Mapped exception to response: 500 (Internal Server Error)
javax.ws.rs.WebApplicationException: com.sun.jersey.api.MessageException: A message body writer for Java class org.basex.api.jaxrx.BXJaxRx$2, and Java type class org.basex.api.jaxrx.BXJaxRx$2, and MIME media type text/xml; omit-xml-declaration=no was not found
at com.sun.jersey.spi.container.ContainerResponse.write(ContainerResponse.java:285)
at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1310)
at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1223)
at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1213)
at com.sun.jersey.spi.container.servlet.WebComponent.service(WebComponent.java:414)
at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:537)
at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:699)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:401)
at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:766)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at org.mortbay.jetty.Server.handle(Server.java:326)
at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:945)
at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:756)
at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:218)
at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
at org.mortbay.jetty.bio.SocketConnector$Connection.run(SocketConnector.java:228)
at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)
Caused by: com.sun.jersey.api.MessageException: A message body writer for Java class org.basex.api.jaxrx.BXJaxRx$2, and Java type class org.basex.api.jaxrx.BXJaxRx$2, and MIME media type text/xml; omit-xml-declaration=no was not found
... 21 more
Thanks for the support again.