Should @Factory methods fire on Entity Identity fields?
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Key: OPENJPA-2109
URL: https://issues.apache.org/jira/browse/OPENJPA-2109
Project: OpenJPA
Issue Type: Question
Components: kernel
Reporter: Jody Grassel
Priority: Minor
Question for the OpenJPA community. Recently I had made an observation with
the following code:
@Entity
public class JAGExternEntity {
@Id
@Externalizer("JAGExternEntity.toLowercaseString")
@Factory("JAGExternEntity.toUppercaseString")
private String id;
@Externalizer("JAGExternEntity.toLowercaseString")
@Factory("JAGExternEntity.toUppercaseString")
private String extString;
...
(Standard default constructor, getter and setter methods)
...
public String toString() {
return "JAGExternEntity [id=" + id + ", extString=" + extString + "]";
}
public static String toLowercaseString(String str) {
return str.toLowerCase();
}
public static String toUppercaseString(String str) {
return str.toUpperCase();
}
}
Test Code (JUnit):
public void test000() throws Exception {
JAGExternEntity jee = new JAGExternEntity();
jee.setId("SomeIdentity");
jee.setExtString("Some External String.");
System.out.println("Pre Persist: " + jee);
em.getTransaction().begin();
em.persist(jee);
System.out.println("Post Persist: " + jee);
em.getTransaction().commit();
System.out.println("Post Commit: " + jee);
em.clear();
em.getTransaction().begin();
Query q = em.createQuery("SELECT e FROM JAGExternEntity e");
List<JAGExternEntity> resultList = q.getResultList();
for (JAGExternEntity find : resultList) {
System.out.println("Query Result: " + find);
em.remove(find);
}
em.getTransaction().commit();
}
And the test output:
517 jag-test INFO [main] openjpa.Runtime - OpenJPA dynamically loaded a
validation provider.
534 jag-test INFO [main] openjpa.Runtime - Starting OpenJPA 2.1.2-SNAPSHOT
576 jag-test INFO [main] openjpa.jdbc.JDBC - Using dictionary class
org.apache.openjpa.jdbc.sql.DerbyDictionary".
Pre Persist: JAGExternEntity [id=SomeIdentity, extString=Some External String.]
Post Persist: JAGExternEntity [id=SomeIdentity, extString=Some External
String.]
Post Commit: JAGExternEntity [id=SomeIdentity, extString=Some External String.]
Query Result: JAGExternEntity [id=someidentity, extString=SOME EXTERNAL
STRING.]
What the above demonstrates is that @Externalizers will fire for all persistent
fields, including identity fields, but @Factories will only fire for
non-identity persistent fields. This creates a one-way transformation
scenario, where externalized values cannot be reversed back for identity
fields. The OpenJPA documentation doesn't contain any text forbidding the use
of @Externalizer or @Factory on identity fields (except for embeddable ids,
which was the only noted exception.)
I would like to hear the opinions of the community on this behavior. Is it a
mistake that @Externalizer is allowed to fire on identity fields, but not
@Factory. Or is it a mistake to allow @Externalizer to be allowed to be used
by the identity field in the first place? Should any kind of transformation on
identity fields even be allowed, because of the data integrity/security issues
that could arise from it?
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