title: Unable to create call adapter for class example.Simple
body: <p>I am using retrofit 2.0.0-beta1 with SimpleXml. I want the retrieve a Simple (XML) resource from a REST service.
  Marshalling/Unmarshalling the Simple object with SimpleXML works fine.</p>
  
  <p>When using this code (converted form pre 2.0.0 code):</p>
  
  <pre><code>final Retrofit rest = new Retrofit.Builder()
      .addConverterFactory(SimpleXmlConverterFactory.create())
      .baseUrl(endpoint)
      .build();
  SimpleService service = rest.create(SimpleService.class);
  LOG.info(service.getSimple("572642"));
  </code></pre>
  
  <p>Service:</p>
  
  <pre><code>public interface SimpleService {
  
      @GET("/simple/{id}")
      Simple getSimple(@Path("id") String id);
  
  }
  </code></pre>
  
  <p>I get this exception:</p>
  
  <pre><code>Exception in thread "main" java.lang.IllegalArgumentException: Unable to create call adapter for class example.Simple
      for method SimpleService.getSimple
      at retrofit.Utils.methodError(Utils.java:201)
      at retrofit.MethodHandler.createCallAdapter(MethodHandler.java:51)
      at retrofit.MethodHandler.create(MethodHandler.java:30)
      at retrofit.Retrofit.loadMethodHandler(Retrofit.java:138)
      at retrofit.Retrofit$1.invoke(Retrofit.java:127)
      at com.sun.proxy.$Proxy0.getSimple(Unknown Source)
  </code></pre>
  
  <p>What am i missing? I know that wrapping the return type by a <code>Call</code> works. But I want the service to return business objects as type (and working in sync mode).</p>
  
  <p><strong>UPDATE</strong></p>
  
  <p>After added the extra dependancies and <code>.addCallAdapterFactory(RxJavaCallAdapterFactory.create())</code> as suggested by different answers, I still get this error:</p>
  
  <pre><code>Caused by: java.lang.IllegalArgumentException: Could not locate call adapter for class simple.Simple. Tried:
   * retrofit.RxJavaCallAdapterFactory
   * retrofit.DefaultCallAdapter$1
  </code></pre>