Play - Websockets - Mongo Async

public class Products extends Controller {

	public WebSocket<String> products() {
			return new WebSocket<String>() {
	
				public void onReady(WebSocket.In<String> in,
						WebSocket.Out<String> out) {
	
					in.onMessage(new F.Callback<String>() {
						public void invoke(String event) {
							Object o = com.mongodb.util.JSON.parse(event);
							BasicDBObject merchantInfo = (BasicDBObject) o;
							String username = merchantInfo.getString("username");
							ObjectMapper mapper = new ObjectMapper();
							
							BasicDBList productJsons = new BasicDBList();
	
							Block<Document> printDocumentBlock = new Block<Document>() {
							    @Override
							    public void apply(final Document product) {
									BasicDBObject productDo = (BasicDBObject) com.mongodb.util.JSON.parse(product.toJson());
									productDo.put("_id", product.getObjectId("_id").toString());
									productJsons.add(productDo);
							    }
							};
							SingleResultCallback<Void> callbackWhenFinished = new SingleResultCallback<Void>() {
							    @Override
							    public void onResult(final Void result, final Throwable t) {
									out.write(productJsons.toString());
							    }
							};
							Document query = new Document();
							query.put("username", username);
							FindIterable<Document> products = Mongo.asyncDatabase().getCollection("products").find(query);
							products.forEach(printDocumentBlock, callbackWhenFinished);
						}
					});
	
				}
			};
		}
	}
}