How can I persist complex entity with Strategy objects in JPA?

Question

I'm using Spring boot JPA to develop a DDD project. I used annotation-based orm to persist the domain objects in DAOs. But now the domain model has become so complex that I consider to perform strategy pattern on Domain Entities.

Here is an example:

@Entity
class ComplexEntity {
    @Id
    private String id;

    // ... other simple fields

    // Example of a strategy object
    // Which deals with complex logics
    private StrategyObject strategyObject;

    // Business methods here
    public void doLogic(OtherEntity other) {
        strategyObject.performOn(other);
        // other logics...
    }
}

When I refactor the domain objects like this, the orm becomes such a serious problem that I almost can't deal with. Is there any solutions to persist this kind of complex domain entities?

Answer 1

Unfortunately, this can not be done with JPA, but Hibernate supports this possibility.

How to implement custom composite user type

Answer 2

I would create an enum

public enum Strategy {

    public abstract StrategyObject getImplementation();

    STRATEGY_1 {
         public StrategyObject getImplementation() {
              return new Strategy1();
         },
    STRATEGY_2 {
         public StrategyObject getImplementation() {
              return new Strategy2();
         }
}

and then reference the Strategy enum in your entity:

@Entity
class ComplexEntity {
    @Id
    private String id;

    @Enumerated(EnumType.STRING)    
    private Strategy strategy;

    public void doLogic(OtherEntity other) {
        strategy.getImplementation().performOn(other);
    }

}

EDIT: I guess I missed the part where the strategies might have a significant amount of configuration that Needs to be stored. But maybe this is a start.