This week's book giveaway is in the OCAJP forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide 1Z0-808 and have Jeanne Boyarsky & Scott Selikoff on-line! See this thread for details.
Its not likely to be anything to do with the classpath. Sounds like you are trying to create an entity with an attribute whose data type allows you to specify a size, and you've specified a size outside the supported range, e.g.varchar(10000000000). Is that the sort of thing you are doing?