Question

Is there a possibility to check if a mongo database allready exists?

Answer 1

Yes, you can get the list of existing databases. From the Java driver you could do something like this to get the database names on a mongod server running on localhost

Mongo mongo = new Mongo( "127.0.0.1", 27017 );
List<String> databaseNames = mongo.getDatabaseNames();

This is equivalent to the mongo shell “show dbs” command. I am sure similar methods exist in all of the drivers.