I've got an object which contains a collection. When I change the object collection
OJB wants to delete the related object in the database.
For example I've got a Book object with a collection of Author object. I've got an n:m
non decomposed relationship and my descriptor don't allows cascade-delete cascade
updates (auto-retrieve="true"/auto-delete="false"/auto-update="false" in my collection
descriptor).
If I do this :
public void updateBook(Book b, Author newAuthor) {
tx.begin();
OQLQuery query = odmg.newOQLQuery();
query.create("select b from " + Book.class.getName() + " where id = " + b.getId();
DList results = (DList) query.execute();
Book myBook = (Book)results.get(0);
tx.lock(myBook , Transaction.WRITE);
myBook.getAuthors().clear();
myBook.getAuthors().add(newAuthor);
tx.commit;
}
OJB delete the indirection table's related values and ALSO the author table values.
If I do this :
public void updateBook(Book b, Author newAuthor) {
tx.begin();
OQLQuery query = odmg.newOQLQuery();
query.create("select b from " + Book.class.getName() + " where id = " + b.getId();
DList results = (DList) query.execute();
Book myBook = (Book)results.get(0);
tx.lock(myBook , Transaction.WRITE);
ArrayList authList = new ArrayList();
authList.add(newAuthor);
myBook.setAuthors(authList);
tx.commit;
}
OJB delete only the indirection table's related values (which is the expected result).
Is it a bug ? Is it a misunderstanding of the framework ?
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About using/design (related question) :
Generally I want to get a domain (business) object from the persistence layer. Then I
use it in my app (webapp), modify it and when modification are validated, update it in
the persistent storage.
I use a class for persistence actions (CRUD) like this :
class BookPersistence {
static BookPersistence getInstance() {...}
Book getBook(String bookId) { ...}
void storeBook(Book b) { ...}
void deleteBook(Book b) { ...}
void updateBook(Book b) { ...}
}
And I use it like this :
Book b = new Book();
BookPersistence.getInstance().store(b);
...
And :
Book b1 = BookPersistence.getInstance().getBook("bookID");
b1.setXXX(...);
...
BookPersistence.getInstance().updateBook(b1);
Whith an update method like this :
public void updateBook(Book b) {
tx.begin();
tx.lock(myBook , Transaction.WRITE);
tx.commit;
}
It doesn work 'cause book is modified outside the transaction and OJB doesn't
"monitor" it (I think).
But I can't open a transaction during all the modification time of my object and
commit at the end, isn't it ?
If I use this object in a webapp (modification by a form), I must wait all the
validation (and request, validation, ...) before commiting. It retains lock during
this time (even if I use optimistic locking, a long time transaction can desynchronize
data with multiple users).
And I've got to add Transaction demarcation in my business process code.
So I try to declare the object dirty in my transaction like this :
public void updateBook(Book b) {
tx.begin();
tx.lock(myBook , Transaction.WRITE);
((TransactionImpl)tx).makeDirty(b);
tx.commit;
}
It generally work but not in the case described above (with a collection) : OJB delete
related collection object data.
And it's not a standardized process (the makeDirty() of TransactionImpl object is not
part of ODMG API).
If I do this :
public void updateBook(Book b) {
tx.begin();
OQLQuery query = odmg.newOQLQuery();
query.create("select b from " + Book.class.getName() + " where id = " + b.getId();
DList results = (DList) query.execute();
Book myBook = (Book)results.get(0);
tx.lock(myBook , Transaction.WRITE);
// I don't think that the following line is usefull 'cause
// the OID of Book b is the same than the Book myBook
// and this object is monitored due to previous query isn't it ?
BeanUtils.copyProperties(b, myBook);
tx.commit;
}
OJB also delete related collection object data (and : b came from a previous select).
So what's the solution ? Do I use bad patterns ? Is it a bug ? Am I too stupid
(pleeeaaase tell me I'm not) ?
Thanks.
