EventBus message body type

client.js

load('vertx.js');

var eb = vertx.eventBus;

vertx.setPeriodic(1000,function(id){

   eb.send(
      'server.address',
      'a String',
      function(reply){
         console.log(reply);
      }
   );
);

server.java

import org.vertx.java.core.*;
import org.vertx.java.core.eventbus.*;
import org.vertx.java.core.json.*;
import org.vertx.java.deploy.*;

public class server extends Verticle {

   public void start(){
      EventBus eb = vertx.eventBus();

      eb.registerHandler(
         "server.address",
         new Handler<Message<JsonObject>>(){
            public void handle(Message<JsonObject> message){
               System.out.println(message.body);

               JsonObject body = message.body;
               System.out.println(body.getString(""));

               JsonObject object =
                  new JsonObject("{ \"reply\":\"message\" }");

               message.reply(object);
            }
         }
      );
   }
}