Dear group,
I would like to know the reason why child value won't be stored when
it's persisted directly by referring as a element of list field of
parent.
In the next testDetach7 JUnit test (which tries to change the value of
existing child entity field),
- chapter child object was not stored by persisting like
pm.makePersistent( b.getChapters().get( 0))
- chapter child object was stored by persisting the parent like by
pm.makePersistent( b);
public void testDetach7() throws Exception {
prepTestObjects();
int originalNumPages = b.getChapters().get( 0).getNumPages();
do {
b.getChapters().get( 0).setNumPages(
new Double( Math.round( Math.random() *
99)).intValue() + 1
);
} while( originalNumPages == b.getChapters().get(
0).getNumPages());
int newNumPages = b.getChapters().get( 0).getNumPages();
/*
pm = pmf.getPersistenceManager();
pm.makePersistent( b.getChapters().get( 0));
Chapter detachedChapter =
(Chapter)pm.detachCopy( b.getChapters().get( 0));
pm.close();
This fails
assertEquals( newNumPages, detachedChapter.getNumPages());
*/
pm = pmf.getPersistenceManager();
pm.makePersistent( b);
Chapter detachedChapter =
(Chapter)pm.detachCopy( b.getChapters().get( 0));
pm.close();
// This will pass
assertEquals( newNumPages, detachedChapter.getNumPages());
}
protected void prepTestObjects() throws Exception {
b = new Book();
b.setTitle( "JDO 4eva");
c1 = new Chapter();
c1.setTitle( "Intro");
c1.setNumPages( 10);
b.getChapters().add( c1);
c2 = new Chapter();
c2.setTitle( "Configuration");
c2.setNumPages( 9);
b.getChapters().add( c2);
pm = pmf.getPersistenceManager();
pm.setDetachAllOnCommit( true);
try {
pm.currentTransaction().begin();
pm.makePersistent( b);
pm.currentTransaction().commit();
} finally {
if (pm.currentTransaction().isActive()) {
pm.currentTransaction().rollback();
}
pm.close();
}
}
/**
* From
http://gae-java-persistence.blogspot.com/2009/10/creating-bidrectional-owned-one-to-many.html
*/
@PersistenceCapable(identityType = IdentityType.APPLICATION,
detachable = "true")
public class Book {
// Prefer String encodedKey over Key class object since it's sharable
with client via serialization
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
@Extension( vendorName = "datanucleus", key = "gae.encoded-pk",
value="true")
protected String encodedKey;
protected String title;
@Persistent(mappedBy = "book", defaultFetchGroup="true")
@Element( dependent = "true")
protected List<Chapter> chapters = new ArrayList<Chapter>();
- getter and setters -
}
@PersistenceCapable( identityType = IdentityType.APPLICATION,
detachable = "true")
public class Chapter {
// Prefer String encodedKey over Key class object since it's sharable
with client via serialization
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
@Extension( vendorName = "datanucleus", key = "gae.encoded-pk",
value="true")
protected String encodedKey;
protected String title;
protected int numPages;
@Persistent( defaultFetchGroup = "true")
protected Book book;
- getter and setters -
}
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