spring + JPA: “Extend” entity classes at load-time from configuration

问题

In my small project I have 3 entity classes. These classes should be "extendable" by the end user by configuration (eg. human readable text based, probably xml). With extendable I mean adding fields and proper JPA annotations (including something like @ManyToOne) to them so the generated class is then a "normal" entity class.

I've already very vaguley heard of javassist, cglib, Aspectj due to using hibernate and spring. However which one would be appropriate to use? Does this work with spring? I mean when the application starts it must

1. create the entities from config
2. start spring context
3. make spring "scan" them (packagesToScan) or Programmatically loading Entity classes with JPA 2.0?

My further question is if there is already some kind of library / tool that includes reading a configuration file and create the entity from it?

来源：https://stackoverflow.com/questions/15394970/spring-jpa-extend-entity-classes-at-load-time-from-configuration