Building an RHQ Client

RHQ exposes a set of APIs that can be used to build a remote client. The CLI is one such consumer of those APIs. The documentation for building your own remote client says to get the needed libraries from the CLI distribution. If you are using a build tool such as Maven, Gradle, Buildr, etc. that provides dependency handling, it would be easier to be provided with the dependency information needed to integrate into your existing build.

Last week I started building my own client and hit a couple snags. The CLI pulls in dependencies from the module rhq-remoting-client-api; so, I hoped that declaring a dependency on that module was all that I needed.

  
    org.rhq
    rhq-remoting-client-api
    3.0.0
  

This pulls in a number of libraries. When I started my simple client though, I got the following error,

java.lang.NoClassDefFoundError: EDU/oswego/cs/dl/util/concurrent/SynchronizedLong (NO_SOURCE_FILE:3)

After a little digging I realized that I needed to add the following dependency.

  oswego-concurrent
  concurrent
  1.3.4-jboss-update1

After rebuilding and restarting my client, I got a different exception.

org.jboss.remoting.CannotConnectException: Can not connect http client invoker. Response: OK/200.
 at org.jboss.remoting.transport.http.HTTPClientInvoker.useHttpURLConnection(HTTPClientInvoker.java:348)
 at org.jboss.remoting.transport.http.HTTPClientInvoker.transport(HTTPClientInvoker.java:137)
 at org.jboss.remoting.MicroRemoteClientInvoker.invoke(MicroRemoteClientInvoker.java:122)
 at org.jboss.remoting.Client.invoke(Client.java:1634)
 at org.jboss.remoting.Client.invoke(Client.java:548)
 at org.jboss.remoting.Client.invoke(Client.java:536)
 at org.rhq.enterprise.client.RemoteClientProxy.invoke(RemoteClientProxy.java:201)
 at $Proxy0.login(Unknown Source)

I started comparing the dependencies that I was pulling in versus what the CLI used. I was definitely pulling in some additional libraries that are not included in the CLI. While the above exception does not convey a whole lot of information, I knew that it was occurring because I had classes on my local classpath that I should be getting from the server. When I managed to get my dependencies to match up with the CLI, I got past the exceptions.

For other folks who want to build their own RHQ client, this dependency situation can be a bit of a mess. Last night I pushed a new module into the RHQ git repo that alleviates this problem. Now you only need the following dependency,

  org.rhq
  remote-client-deps
  4.0.0-SNAPSHOT
  pom

With this, you will pull in only those dependencies that are needed to build your own RHQ client. You do not need to declare any additional RHQ dependencies. You can view the source for the remote-cliet-deps module here.