title: How to get result from multiple query on multiple collection of mongo in eventBus vertx2?
body: <p>I am working on providing API and I am storing data by month a database and by date a collection on mongodb.</p>
  
  <p>So I have db <code>db_08_2015</code> then I have 31 collection from <code>date_01</code> to <code>date_31</code>
  and I have to query data from date 1 to date 10 to have a  total money spend so I need to send 31 request like this.</p>
  
  <p>My question is How to get data by 1 request at the time to get a sum before I return to client like sync request into mongo to get result.
  Something like I have date_01 = 10 then date_02 = 20 ... and I want to sum it all before return to client.</p>
  
  <pre><code>vertx.eventBus().send("mongodb-persistor", json, new Handler&lt;Message&lt;JsonObject&gt;&gt;() {
                  @Override
                  public void handle(Message&lt;JsonObject&gt; message) {
                      logger.info(message.body());
                      JsonObject result = new JsonObject(message.body().encodePrettily());
                      JsonArray r = result.getArray("results");
                      if (r.isArray()) {
                          if (r.size() &gt; 0) {
                              String out = r.get(0).toString();
                              req.response().end(out);
                          } else {
                              req.response().end("{}");
                          }
                      } else {
                          req.response().end(message.body().encodePrettily());
                      }
                  }
              });
  </code></pre>