Integration testing of a REST API - decorate utilities

DecorateUtil.java

public static < T >HttpEntityEnclosingRequest decorateRequestWithResource
      ( final HttpEntityEnclosingRequest request, final T resource ) 
      throws IOException{
   Preconditions.checkNotNull( request );
   Preconditions.checkNotNull( resource );
   
   final String resourceAsJson = JsonUtil.convertResourceToJson( resource );
   return JsonUtil.decorateRequestWithJson( request, resourceAsJson );
}

public static HttpEntityEnclosingRequest decorateRequestWithJson
      ( final HttpEntityEnclosingRequest request, final String json ) 
      throws UnsupportedEncodingException{
   Preconditions.checkNotNull( request );
   Preconditions.checkNotNull( json );
   
   request.setHeader( HttpConstants.CONTENT_TYPE_HEADER, "application/json" );
   request.setEntity( new StringEntity( json ) );
   
   return request;
}

This gist is used in:
http://www.baeldung.com/2011/10/13/integration-testing-a-rest-api/