Java Persistence Query Language

Enumerated Annotation in GlassFish Persistence

Several users ran into problems using Enumerated annotation in combination with Java Persistence Query Language (JPQL). Here is an example showing user how to use @Enumerated annotation correctly.

An Enumerated annotation specifies that a persistent property or field should be persisted as an enumerated type. An enum can be mapped as either a string or an integer. There are two enumerated types: ORDINAL and STRING. If the enumerated type is not specified, the enumerated type is assumed to be ORDINAL.

Here is an example about how to define enum and use Enumerated annotation in persistence class:

In persistence class Item.java, EmployeeStatus is an enum. And the field status in Item is defined as EmployeeStatus and is mapped to an integer.

@Entity
@Table(name="ITEM_TABLE")
public class Item implements java.io.Serializable {
public enum EmployeeStatus { FULL_TIME, PART_TIME, CONTRACT };

@Id
@Column(name="ID")
private Integer itemId;
private String name;
@Enumerated(ORDINAL)
private EmployeeStatus status;

public Item() {}

public Integer getItemId() {
return itemId;
}

public void setItemId(Integer id) {
this.itemId = id;
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

public void setStatus(EmployeeStatus status) {
this.status = status;
}

public EmployeeStatus getStatus() {
return status;
}
}

When using JPQL to query status from client, below is the sample code in j2se environment.

// Create EMF for a persistence unit called j2seEnvironment.
EntityManagerFactory emf =
Persistence.createEntityManagerFactory("j2seEnvironment");

// create EM
EntityManager em = emf.createEntityManager();

// get Transaction
EntityTransaction tx = em.getTransaction();

// create Item and insert into database
Item item = new Item();
item.setItemId(new Integer(1));
item.setName("Jie Leng");
item.setStatus(Item.EmployeeStatus.FULL_TIME);
tx.begin();
em.persist(item);
tx.commit();

// run a JPQL query
String ejbql = "SELECT i FROM Item i WHERE i.status = :status";
Query query = em.createQuery(ejbql);
query.setParameter("status", Item.EmployeeStatus.FULL_TIME);
List result = query.getResultList();

I saw some users using wrong JPQL query like following code and got errors:

// wrong code
String ejbql2 = "SELECT i FROM Item i WHERE i.status = 0";
Query query2 = em.createQuery(ejbql2);
List result2 = query2.getResultList();

Since status is enum type, you can not just using integer directly in where clause.

Posted at 04:50AM May 01, 2006 by jielin in Sun  |  Comments[8]