Check if mongodb database exists?

For anyone who comes here because the method getDatabaseNames(); is depreciated / not available, here is the new way to get the list of existing databases:

MongoClient mongoClient = new MongoClient();
MongoCursor<String> dbsCursor = mongoClient.listDatabaseNames().iterator();
while(dbsCursor.hasNext()) {
    System.out.println(dbsCursor.next());
}

Here is a method that validates if the database is found:

public Boolean databaseFound(String databaseName){
    MongoClient mongoClient = new MongoClient(); //Maybe replace it with an already existing client
    MongoCursor<String> dbsCursor = mongoClient.listDatabaseNames().iterator();
    while(dbsCursor.hasNext()) {
        if(dbsCursor.next().equals(databaseName))
            return true;
    }
    return false;
}

From the shell, if you want to explicitely check that a DB exists:

db.getMongo().getDBNames().indexOf("mydb");

Will return '-1' if "mydb" does not exist.

To use this from the shell:

if [ $(mongo localhost:27017 --eval 'db.getMongo().getDBNames().indexOf("mydb")' --quiet) -lt 0 ]; then
    echo "mydb does not exist"
else
    echo "mydb exists"
fi

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.