Add openConnection

git-svn-id: https://svn.d4science.research-infrastructures.eu/gcube/trunk/data-publishing/document-store-lib--mongodb@142226 82a268e6-3cf1-43bd-a215-b396298e98cf

src/main/java/org/gcube/documentstore/persistence/PersistenceMongoDB.java

@@ -88,6 +88,12 @@ public class PersistenceMongoDB extends PersistenceBackend {
 		mongoClientOptions = MONGO_CLIENT_OPTIONS;
 	}
 	
+	@Override
+	protected void openConnection() throws Exception {
+		logger.trace("openConnection");
+	}
+	
+	
 	@Override
 	public void close() throws Exception {
 		mongoClient.close();