Hibernate Annotation using base entity

问题:

In my project I have a POJO called BaseEntity as shown below.

class BaseEntity{
    private int id;
    public void setId(int id){
        this.id=id;
    }
    public int getId(){
        return id;
    }
}

And a set of other POJO entity classes like Movie, Actor,...

class Movie extends BaseEntity{
    private String name;
    private int year;
    private int durationMins;
    //getters and setters
}

I'm using BaseEntity only for using it as a place holder in some interfaces. I never have to store a BaseEntity object. I have to store only the entity objects extended from BaseEntity. How should I annotate these classes so that I get one table per entity extended from the BaseEntity. For movie it should be like (id, name, year, durationMins).

回答1:

I found the answer in a totally unrelated post. I just have to annotate BaseEntity as @MappedSuperclass. The following code done what I needed.

@MappedSuperclass
class BaseEntity {
    @Id
    private int id;
    //getters and setters.
}
@Entity
class Movie extends BaseEntity {
    @Column
    private String name;
    @Column
    private int year;
    @Column
    private int durationMins;
    //getters and setters
}

回答2:

You can use @MappedSuperClass on your BaseEntity, and have Movie extend it.

@MappedSuperClass
class BaseEntity {
    @Id
    private int id;
    ...
}

class Movie extends BaseEntity {
    ...
}

回答3:

What you need is Table Per Concrete class strategy. And you do not need any annotation for your BaseEntity in this strategy. Have a look at this for more explanation.