CODEWITHSUNDEEP
javasqljpaprimary-keycomposite-primary-key
Ravindu
Ravindu

Reputation: 2550

Use Objects as Primary keys and Composite keys in JPA

I want to know whetheris it a GOOD practise to use Objects as composite keys in JPA. For example I have few composite keys and the are foreign keys from another tables and mapped with them.

Composite Class

@Embeddable
public class CashInstrumentComposite implements Serializable {


  private static final long serialVersionUID = -6065538857637001219L;

  @Column(name = "instrument_id", nullable = false)
  private String instrumentId;

  @OneToOne
  @JoinColumn(name = "company_id")
  private Company companyId;

  @Column(name = "instrument_type", nullable = true)
  @Enumerated(EnumType.STRING)
  private InstrumentType instrumentType;

  @Column(name = "batch_no", nullable = false)
  private String batchNumber;
}

Entity Class

@Entity
@Table(name = "bank_corporate_cash_instrument")
public class CashInstrument extends Model {

/* serial version id. */
private static final long serialVersionUID = 8360452197690274885L;

/* specify the composite key */
@EmbeddedId
private CashInstrumentComposite compositeId;

I can persist using this without any problem, BUT I read this,

http://docs.oracle.com/javaee/6/tutorial/doc/bnbqa.html#bnbqf

It says there that primarykey should be one of

So what did I do wrong here? Please explain.Thank You

Upvotes: 1

Views: 2021

Answers (3)

Ravindu
Ravindu

Reputation: 2550

Ok, I did some sample apps I looks like I can use objects as composite keys. But I'm still confuse about whats written in this documentation

http://docs.oracle.com/javaee/6/tutorial/doc/bnbqa.html#bnbqf

But it's not a good practice to use composite keys because when u use one of the key in the composite key as a foreign key, then you have to duplicate the rest of the keys in that composite also. This is a waste specially if you have 4-5 keys as a composite.

Upvotes: 0

Steve C
Steve C

Reputation: 19445

I think that you have not interpreted what that piece of documentation says correctly:

The primary key, or the property or field of a composite primary key, must be one of the following Java language types:

Upvotes: 1

maress
maress

Reputation: 3533

@EmbeddedId from javadoc

Is applied to a persistent field or property of an entity class or mapped superclass to denote a composite primary key that is an embeddable class. The embeddable class must be annotated as Embeddable. Example:

@EmbeddedId
protected EmployeePK empPK;

And the EmployeeKey:

@Embeddable
public class EmployeePK {
 private Long key1;
 private Long key2;
}

You can have a look at:

Oracle Doc

Upvotes: 0

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