title: Not able to get the aggregate result in mongo embedded document by querying
body: <p>Issue in querying the embedded document in mongo db. I am trying to get the <code>conversationId</code> for the users but it returning null.</p>
  
  <p>Sample document:</p>
  
  <pre><code>{
  "_id" : ObjectId("5787391f191fda3a4430c749"),
  "conversationId" : "fWFGIr0xAbQytmVcQIPV",
  "user" : [{_id : "800", "name" : "Tim"},{_id : "500", "name" : "Kingsley"},
  {_id : "400", "name" : "Roger"}],
  "type" : "PRIVATE"
  }
  </code></pre>
  
  <p>Query:</p>
  
  <pre><code>Aggregation agg = newAggregation(
              match(Criteria.where("type").is("PRIVATE")),
              group("conversationId").push("user.id").as("users"),
              match(Criteria.where("users").all(Arrays.asList('800','400','500')))
              );
      AggregationResults&lt;Rooms&gt; groupResults = mongoOps.aggregate(agg, ROOMS, Rooms.class);
        List&lt;Rooms&gt; result = groupResults.getMappedResults();
        result.get(0).getId() // returns null
  </code></pre>
  
  <p>The <code>result.get(0).getId()</code> is returning null, as per my query I am expecting the conversation Id that is present for the users.</p>