#13 Retrieve & validate all metadata before deleting generated files

[Vladimir Alarcon]

It would be useful to retrieve and validate all JDBC metadata before removing existing generated files, in order to supersede them with the new ones.

Currently it's common to delete all generated files (DAO primitives, mappers primitives, MyBatis config files) BEFORE the new generation of file. If the generation crashes, the developer ends up with no DAOs at all and the project doesn't even compile... until the generation is fixed.