Hi,
I am working on an application using seam 2.1.2 , deployed on Apache Tomcat 6.0.2 and mySql 5.0.67. I have 2 models called Branch and Supplier , with a one-to-many relationship between Branch and Supplier .

public class Branch { 
............................
private Set<Supplier> suppliers = new HashSet<Supplier>(0);
............................
@OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY, mappedBy = "branch")
        public Set<Supplier> getSuppliers() {
                return this.suppliers;
        }

        public void setSuppliers(Set<Supplier> suppliers) {
                this.suppliers = suppliers;
        }
}

public class Supplier {
.............................
private Branch branch;
..............................
@ManyToOne(fetch = FetchType.LAZY)
        @JoinColumn(name = "branch_id")
        @NotNull
        public Branch getBranch() {
                return this.Branch;
        }

        public void setBranch(Branch branch) {
                this.branch = branch;
        }
}

The DAO's that I am using :-

To save supplier -

public void save(Supplier supplier) {
                UserTransaction tx = Transaction.instance();
                try {
                        if(!tx.isActiveOrMarkedRollback()){
                                tx.begin();
                        }
                        log.info("supplier id before persist : "+supplier.getId());
                        entityManager.persist(supplier);
                        log.info("supplier id after persist : "+supplier.getId());
                        entityManager.flush();
                        log.info("supplier id after flush : "+supplier.getId());
                        tx.commit();
                        tx.begin();
                } catch (SystemException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                } catch (NotSupportedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                } catch (SecurityException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                } catch (IllegalStateException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                } catch (RollbackException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                } catch (HeuristicMixedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                } catch (HeuristicRollbackException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                }
        }

To update the Branch :-

public void update(PartPrice partPrice) {
                log.info("Before merge : Size of supplier set : "+partPrice.getSuppliers().size());
                entityManager.merge(partPrice);
                log.info("Before flush , after merge : Size of supplier set : "+partPrice.getSuppliers().size());
                entityManager.flush();
                log.info("After flush : Size of supplier set : "+partPrice.getSuppliers().size());
        }

Other information that could be of significance :-
1.Both the models have an overridden equals and hashcode method
2.The Dao's are Application Scoped
3.I am using DTO for capturing Data from the form , and then saving/deleting/updating it

My Problem :

1. A supplier is created and saved , for a Branch that has no suppliers as of now . This is of significance as , the problem is not encountered if the Branch has at least one supplier .

2. After the supplier is persisted (it is visible in the db) , I call a function to update the associated Branch . As you can see in my Dao for updating Branch  , I am displaying the size of the supplier set before and after the update . The problem is that , as soon as the update happens , the supplier set for that Branch becomes empty . I cannot see the suppliers for that Branch on the webpage , or on my console .

3. If I keep adding more suppliers , the same behavior is observed . If , I do a refresh on the webpage , I can see the supplier list , and any supplier which is subsequently added . As I said before , this problem occurs only when there are no suppliers for a branch , and I add a new one .

So where am I going wrong ?