Oracle TopLink and OpenJPA different behaviour

[Łukasz Budnik]

Hi All!

I have a problem while migrating from Oracle TopLink to OpenJPA.

I have two very simple tables one to many: one dw_modules can have
many dw_pages.

Those tables are very simple:
dw_modules has a primary key: "id"
dw_pages has a primary key: "id" and a foreign key "parentmodule_id"

I have automatically generated class entities:

DWModule with

@OneToMany(mappedBy = "parentmoduleId")
    private Collection<DWPage> dWPageCollection;

and DWPage with:

@JoinColumn(name = "PARENTMODULE_ID", referencedColumnName = "ID")
    @ManyToOne
    private DWModule parentmoduleId;


Also, I have a standalone application to test it.

public static void main(String[] args) {
        EntityManager em = emf.createEntityManager();
        DWModule module = (DWModule)
em.createNamedQuery("DWModule.findById").setParameter("id",
3).getSingleResult();
        System.out.println(module.getName());
        for (DWPage page: module.getDWPageCollection()) {
            System.out.println("\t- " + page.getName());
        }
    }

First of all I have tested my current solution (Oracle TopLink), the
result is as predicted, everything is OK:

Search
        - BasicPatientSearch
        - ExaminationByDiagnosisSearch
        - ExaminationByDescriptionSearch

Now, I have changed to OpenJPA provider and run the program again, the
result is:

Search
Exception in thread "main" java.lang.NullPointerException
        at jpatests.Runner.main(Runner.java:37)

Search is the name of the module

BUT I get a null pointer on this line:

for (DWPage page: module.getDWPageCollection()) {

so I changed:

@OneToMany(mappedBy = "parentmoduleId", fetch= FetchType.LAZY)
    private Collection<DWPage> dWPageCollection;

nope, still null pointer, once again:

@OneToMany(mappedBy = "parentmoduleId", fetch= FetchType.EAGER)
    private Collection<DWPage> dWPageCollection;

yes, this time DWPage collection is not null and the result as expected.

I have over 50 tables (and entities) with probably more than 50 collections...
do I have to change ALL classes?

or is there a way to make OpenJPA fetch all collections like Oracle
TopLink (at least at the LAZY level).

best regards
Łukasz