@POST
@Path("{id}")
@Produces("application/json")  
@Consumes("application/json")  
public JSONObject sayPlainTextHello(@PathParam("id")JSONObject inputJsonObj) {  
String input = (String) inputJsonObj.get("input");  
String output="The input you sent is :"+input;  
JSONObject outputJsonObj = new JSONObject();  
outputJsonObj.put("output", output);  
return outputJsonObj;  
}

Client:

ClientConfig config = new DefaultClientConfig();  
Client client = Client.create(config);  
WebResource service = client.resource(getBaseURI());  
JSONObject inputJsonObj = new JSONObject();  
inputJsonObj.put("input", "Value"); System.out.println(service.path("rest").path("hello").accept(MediaType.APPLICATION_JSON).entity(inputJsonObj).post(JSONObject.class,JSONObject.class));