Hibernate: entity class name as identifier

Question

I want to make my entity a singleton. That singleton should be accessible from other entities.

So I decide to set its id manyally, like:

@Entity
@Table(name = "tableName")
public class SingletonEntity {

  @Id
  private int id = this.getClass().getSimpleName(); //IS IT POSSIBLE? HOW?

  //.......
}

Question:

How to achieve that? Please. give me an example.

EDIT:

It is worth to say that my SingletonEntity has only final string state. So I can say that its stateless. Actually, I don't want a singleton, I only want to set final id to that entity, and I want that id should be equals to SingletonEntity.class.getSimpleName()

For @Balaji Reddy:

I've tried:

@Entity
@Table(name = "Client")
public class Client implements Serializable {

    @Id
    @Column(name = "id")
    private static final String id = Client.class.getSimpleName();

    .................
}

And get:

No identifier specified for entity: db.Client

in string

ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");

@Alberto Solano, yes I've read ). I've implemented a State Pattern. Each of my states is a singleton. I can make them a spring beans, but there is a little problem. Each of those states has it own state (final in my case). So if I make them a spring beans I need to recompiling my app each time I want to change their state. I see the solution in making them a singleton entities. See also stackoverflow.com/questions/20091168/… — VB_
– VB_, Commented Nov 20, 2013 at 9:26
I don't understand exactly what you are asking. Perhaps you should take a look at IOC frameworks that manage singletons way better than manually done with static fields / functions. I think you should change your question about: initialization of field of entity by the class simple name. — zenbeni
– zenbeni, Commented Nov 20, 2013 at 11:17
I have Spring's singleton beans. I look for correct way to replace those beans with hibernate entities. — VB_
– VB_, Commented Nov 20, 2013 at 11:19

zenbeni · Accepted Answer · 2013-11-20 11:05:46Z

1

Did you try using a constant?

private static final String CLASS_NAME = SingletonEntity.class.getSimpleName();

@Id
private String id = CLASS_NAME;

This is the initialization of the field of your entity, you can also do this in the constructor.

private SingletonEntity() {
    this.id = this.getClass.getSimpleName();
}

answered Nov 20, 2013 at 11:05

zenbeni

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zenbeni Over a year ago

@NickoleAbs for the same id, the same columns will be updated in your datastore, if it is not the case check your mapping + database. You should not worry about that, primary keys are by definition unique. Maybe you are looking for disabling rewriting of an existing entity which is a different case.

Trying · Accepted Answer · 2013-11-20 11:05:27Z

1

@Entity
@Table(name = "tableName")
public class SingletonEntity {

  @Id
  private static int id = this.getClass().getSimpleName(); //try something like this.

  //.......
}

Check EJB Specifications 3.1

edited Nov 20, 2013 at 11:05

Trying

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answered Nov 20, 2013 at 10:16

Balaji Reddy

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2 Comments

VB_ Over a year ago

Does it work for you? I can try only after a large refactoring; just want to be certain about that. And what about final? I want to be certain that noone can store in DB two entities of one class .

VB_ Over a year ago

It doesn't work for me. Look at 'For @Balaji Reddy' section of my question

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