注释包含 JPA 中的非实体类的 Map

Question

Is it possible to use a map with a non-entity class in JPA? If yes, how should it be annotated correctly?

@Entity
class A {

   @HowShouldIAnnotateThis?
   private Map<B, Integer> myMap = new HashMap<B, Integer>();

}

@Entity
class B {
 ...
}

Answer 1

You cannot do this with JPA 1.0. Some implementations provide proprietary extensions (such as EclipseLink's @BasicMap ) which you could use if you don't mind coupling your application to the given JPA provider.

JPA 2.0 will provide similar functionality with @ElementCollection .