The query returns no result.
ApiProxy.setEnvironmentForCurrentThread(new TestEnvironment
());
ApiProxy.setDelegate(new ApiProxyLocalImpl(new File("."))
{
});
A a = new A("A");
B b = new B("B");
a.getBs().add(b);
PersistenceManagerFactory pmf =
JDOHelper.getPersistenceManagerFactory("transactions-optional");
PersistenceManager pm = pmf.getPersistenceManager();
Transaction tx = pm.currentTransaction();
try {
tx.begin();
pm.makePersistent(a);
tx.commit();
} finally {
if (tx.isActive()) {
tx.rollback();
}
}
System.out.println(a.getKey());
A ap = pm.getObjectById(A.class, "A");
System.out.println(ap.getKey());
Query query = pm.newQuery(B.class);
query.setFilter("name == nameParam");
query.declareParameters("String nameParam");
List<B> rs = (List<B>) query.execute("B");
System.out.println(rs.size());
On Jan 23, 12:20 am, John Patterson <jdpatter...@gmail.com> wrote:
> Execute a query on the name property of B rather than loading it by
> key. If the name is unique the result should only contain one B.
>
> On 23 Jan 2010, at 11:41,Sydneywrote:
>
>
>
> > I have a one to many relationship. There is a problem in the way I
> > query for a B object. I was wondering what is the best way (most
> > efficient) to do that.
>
> > A a = new A("A");
> > B b = new B("B");
> > a.getBs().add(b);
> > pm.makePersistent(a); // it's done inside a transaction
> > A ap = pm.getObjectById(A.class, "A"); // FINE
> > B bp = pm.getObjectById(B.class, "B"); // NOT FOUND Exception
>
> > I guess B is not found because the real key is not B but B + A key.
> > How do you get the B object when you don't know nothing about A?
>
> > public class A {
>
> > �...@primarykey
> > �...@persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
> > �...@extension(vendorName = "datanucleus", key = "gae.encoded-pk",
> > value = "true")
> > private String key;
> > �...@persistent
> > �...@extension(vendorName = "datanucleus", key = "gae.pk-name", value
> > = "true")
> > private String name;
> > �...@persistent(mappedBy = "a")
> > private List<B> bs;
>
> > public A(String name) {
> > this.name = name;
> > bs = new ArrayList<B>();
> > }
> > ... Getter/Setter
> > }
>
> > @PersistenceCapable(identityType =
> > javax.jdo.annotations.IdentityType.APPLICATION)
> > public class B {
>
> > �...@primarykey
> > �...@persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
> > �...@extension(vendorName = "datanucleus", key = "gae.encoded-pk",
> > value = "true")
> > private String key;
> > �...@persistent
> > �...@extension(vendorName = "datanucleus", key = "gae.pk-name", value
> > = "true")
> > private String name;
> > �...@persistent
> > private A a;
>
> > public B(String name) {
> > this.name = name;
> > }
> > ... Getter/Setter
> > }
>
> > --
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