OK, so I am working on and transferring files between my local machine and a production server.  I move the files from the prod server to check them out on my machine.  They are classes that connect to a MySQL database.  I fire everything up and the console fills with all sorts of exceptions, dolphin crap and such.  Here are the error messages in the console:

Unable to connect due to sql exception
com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Cannot load connection class because of underlying exception: 'java.lang.NumberFormatException: For input string: "null"'.
Cannot load connection class because of underlying exception: 'java.lang.NumberFormatException: For input string: "null"'.
Cannot load connection class because of underlying exception: 'java.lang.NumberFormatException: For input string: "null"'.

 So first I check to see if I can ping the database. I can. The database tool works fine. As it turns out, I still had the database credentials pointing the ones in the production server. On my dev machine, they are a lot simpler.

It wasn't connecting to the database, but it wasn't exactly explicitly telling me that.

Hope this helps someone.