JAX-RS 2 client in RHQ (plugins)

When my fellow Red Hatter Bill Burke recently wrote about the new features in JAX-RS 2.0, I started to consider using the new Client api to use in tests and plugins. Luckily Bill provided a 3.0-beta-1 release of RESTEasy that I started with.

To get this going, I started with the plugin case and wrote my few lines of code in the editor. All red, as the classes were not known yet. After many iterations in the editor and the standalone-pc, I ended up with this list of dependencies, which all need to be included in the final plugin jar:

                <artifactItem>
                   <groupId>org.jboss.resteasy</groupId>
                   <artifactId>resteasy-client</artifactId>
                </artifactItem>
                <artifactItem>
                  <groupId>org.jboss.resteasy</groupId>
                  <artifactId>jaxrs-api</artifactId>
                </artifactItem>
                <artifactItem>
                  <groupId>org.jboss.resteasy</groupId>
                  <artifactId>resteasy-jaxrs</artifactId>
                </artifactItem>
                <artifactItem>
                  <groupId>org.apache.httpcomponents</groupId>
                  <artifactId>httpclient</artifactId>
                </artifactItem>
                <artifactItem>
                  <groupId>org.apache.httpcomponents</groupId>
                  <artifactId>httpcore</artifactId>
                </artifactItem>
                <artifactItem>
                  <groupId>org.jboss.resteasy</groupId>
                  <artifactId>resteasy-jackson-provider</artifactId>
                </artifactItem>
                <artifactItem>
                  <groupId>org.codehaus.jackson</groupId>
                  <artifactId>jackson-jaxrs</artifactId>
                </artifactItem>
                <artifactItem>
                  <groupId>org.codehaus.jackson</groupId>
                  <artifactId>jackson-core-asl</artifactId>
                </artifactItem>
                <artifactItem>
                  <groupId>org.codehaus.jackson</groupId>
                  <artifactId>jackson-mapper-asl</artifactId>
                </artifactItem>
              </artifactItems>

Still I got errors that there is no provider for a media type of application/json available. It turned out, that the RHQ plugin container's classloader does not honor the META-INF/services/javax.ws.rs.ext.Providers entry (or any of the services there, so I had to explicitly enable them in code:

javax.ws.rs.client.Client client = ClientFactory.newClient();
client.configuration().register(org.jboss.resteasy.plugins
      .providers.jackson.ResteasyJacksonProvider.class);
client.configuration().register(org.jboss.resteasy.plugins
      .providers.jackson.JacksonJsonpInterceptor.class);

Now the client works as intended. At there is quite a number of jars involved, I am thinking of providing an abstract REST plugin, that provides the jars and the basic connection functionality, so that other plugins can build on top just like we have done that with the jmx-plugin.

I was also trying to get this to work with Jersey, but failed somewhere in the maven world, as it failed for me after downloading half of the Glassfish distribution.

One interesting question to me is about the target group of this JAX-RS 2.0 client framework, as the Jersey and RESTEasy implementations seem to grow rather large (which does not matter too much for servers or on the desktop), so that Android apps are less likely to use that and will rather fall back to home grown solutions. With the huge number of mobile phones, this could perhaps the end also mean that nobody will touch the Client framework and falls back to those smaller homegrown solutions on mobile and desktop.