Right now Forge's field plugin supports most of the common Java/JPA types as commands (string, number, date, etc.). It also supports JPA relationships (one-to-many, etc.). However, a very common scenario for a Java EE developer is to store an image or other binary object into the database.
In such situations the JPA best practices say that it should be declared as byte array field and annotated with @Lob.
Forge should be able to generate such fields when the command:
The exact name of the command (lob or bytearray or anything) is subject to discussion.