Hi, I tried to build a simple Rest client with resteasy 4.4.0: @Path("/v2/store") public interface IStoreService { @GET @Path("inventory") @Produces(MediaType.APPLICATION_JSON) Response getInventory(); } public class ServiceTest { public static IStoreService createStoreService() throws URISyntaxException { ResteasyClient client = new ResteasyClientBuilderImpl().build(); ResteasyWebTarget target = client.target(new URI(" https://petstore.swagger.io/")); return target.proxy(IStoreService.class); } public static Response test() throws URISyntaxException { IStoreService storeService = createStoreService(); return storeService.getInventory(); } } Works nicely as a standalone java project. But once I try to push this to an Eclipse plugin project for RCP, things start to fail. I put everything into a single plugin, packing all resteasy jars into the plugin to have them available using the sample plugin classloader. Still ServiceTest.test() fails throwing an exception (see below). Anyone ever tried to do such a thing? What am I missing? thanks Christian Exception: Java Stacktrace: java.lang.RuntimeException: java.lang.RuntimeException: RESTEASY003940: Unable to instantiate MessageBodyReader at org.jboss.resteasy.plugins.providers.RegisterBuiltin.register(RegisterB uiltin.java:88) at org.jboss.resteasy.plugins.providers.RegisterBuiltin.getClientInitializ edResteasyProviderFactory(RegisterBuiltin.java:64) at org.jboss.resteasy.client.jaxrs.internal.ResteasyClientBuilderImpl.getP roviderFactory(ResteasyClientBuilderImpl.java:354) at org.jboss.resteasy.client.jaxrs.internal.ResteasyClientBuilderImpl.buil d(ResteasyClientBuilderImpl.java:367) at com.codeandme.restclient.resteasy.ServiceFactory.createStoreService(Ser viceFactory.java:16) at com.codeandme.restclient.resteasy.ServiceFactory.test(ServiceFactory.ja va:22) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.ja va:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccesso rImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at org.mozilla.javascript.MemberBox.invoke(MemberBox.java:126) at org.mozilla.javascript.NativeJavaMethod.call(NativeJavaMethod.java:225) at org.mozilla.javascript.optimizer.OptRuntime.callProp0(OptRuntime.java:8 5) at org.mozilla.javascript.gen.c_5._c_script_0(Unknown Source) at org.mozilla.javascript.gen.c_5.call(Unknown Source) at org.mozilla.javascript.ContextFactory.doTopCall(ContextFactory.java:405 ) at org.mozilla.javascript.ScriptRuntime.doTopCall(ScriptRuntime.java:3508) at org.mozilla.javascript.gen.c_5.call(Unknown Source) at org.mozilla.javascript.gen.c_5.exec(Unknown Source) at org.mozilla.javascript.Context.evaluateReader(Context.java:1293) at org.eclipse.ease.lang.javascript.rhino.RhinoScriptEngine.internalExecut e(RhinoScriptEngine.java:219) at org.eclipse.ease.lang.javascript.rhino.RhinoScriptEngine.execute(RhinoS criptEngine.java:198) at org.eclipse.ease.AbstractScriptEngine.inject(AbstractScriptEngine.java: 226) at org.eclipse.ease.AbstractScriptEngine.run(AbstractScriptEngine.java:277 ) at org.eclipse.core.internal.jobs.Worker.run(Worker.java:63) Caused by: java.lang.RuntimeException: RESTEASY003940: Unable to instantiate MessageBodyReader at org.jboss.resteasy.core.providerfactory.ClientHelper.processProviderCon tracts(ClientHelper.java:152) at org.jboss.resteasy.core.providerfactory.ResteasyProviderFactoryImpl.pro cessProviderContracts(ResteasyProviderFactoryImpl.java:884) at org.jboss.resteasy.core.providerfactory.ResteasyProviderFactoryImpl.reg isterProvider(ResteasyProviderFactoryImpl.java:876) at org.jboss.resteasy.core.providerfactory.ResteasyProviderFactoryImpl.reg isterProvider(ResteasyProviderFactoryImpl.java:863) at org.jboss.resteasy.plugins.providers.RegisterBuiltin.registerProviders( RegisterBuiltin.java:172) at org.jboss.resteasy.plugins.providers.RegisterBuiltin.register(RegisterB uiltin.java:84) ... 24 more Caused by: java.lang.RuntimeException: java.lang.ClassNotFoundException: org.glassfish.jersey.internal.RuntimeDelegateImpl cannot be found by javax.ws.rs_2.0.1.v201504171603 at javax.ws.rs.ext.RuntimeDelegate.findDelegate(RuntimeDelegate.java:152) at javax.ws.rs.ext.RuntimeDelegate.getInstance(RuntimeDelegate.java:120) at javax.ws.rs.core.MediaType.valueOf(MediaType.java:179) at org.jboss.resteasy.core.providerfactory.ClientHelper.addMessageBodyRead er(ClientHelper.java:449) at org.jboss.resteasy.core.providerfactory.ClientHelper.processProviderCon tracts(ClientHelper.java:146) ... 29 more Caused by: java.lang.ClassNotFoundException: org.glassfish.jersey.internal.RuntimeDelegateImpl cannot be found by javax.ws.rs_2.0.1.v201504171603 at org.eclipse.osgi.internal.loader.BundleLoader.findClassInternal(BundleL oader.java:511) at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.ja va:422) at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.ja va:414) at org.eclipse.osgi.internal.loader.ModuleClassLoader.loadClass(ModuleClas sLoader.java:153) at java.lang.ClassLoader.loadClass(ClassLoader.java:357) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:264) at javax.ws.rs.ext.FactoryFinder.newInstance(FactoryFinder.java:115) at javax.ws.rs.ext.FactoryFinder.find(FactoryFinder.java:225) at javax.ws.rs.ext.RuntimeDelegate.findDelegate(RuntimeDelegate.java:135) ... 33 more _______________________________________________ resteasy mailing list resteasy(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/resteasy