My question revolves around remote interfaces and using the persistence API. An
example might give more insight into my question?
I have 3 tables Customer, Order, LineItem with the corresponding object
associations:
| class Customer {
|
| long id;
| List<Order> orders;
|
| public long getId() {};
| public List<Order> getOrders(){};
| }
|
| class Order {
|
| long id;
| List<LineItem> lineItems;
|
| public long getId() {};
| public List<LineItem> getLineItems() {};
| public Customer getCustomer() {};
| }
|
| Class LineItem {
|
| long id;
|
| public long getId() {};
| public Order getOrder() {};
| }
|
When using a session bean that implements a remote interface I make a call
similar to the following?
| @Stateless
| class OrderBean implements RemoteOrder {
|
| public List<Order> getOrders(long custId) {
| return em.createNamedQuery(?order.findByCustomerId?)
| .setParmater(?custId?, custId)
| .getResultList();
| }
| }
|
1)
Now this would work great in a Servlet/JSP that was running in the same JVM,
but I am accessing this from a web service. I am wondering what is the
?standard? way to return the persistent data to the web service client? Is it
off load everything into value objects? Something has to be done otherwise I
will always get exceptions when trying to access the lazy children of Customer.
Even if I do a FETCH JOIN for Customer.orders then the problem nest down to
Order.lineItems, should I FETCH JOIN this to?
2)
What about the cyclic call during marhsalling from Customer.getOrders() then
Orders.getCustomers()? I have yet to find documentation ?anywhere? ;) that
defines a standard way to handle this or should we still develop the J2EE way
and use Transfer Objects (J2EE design Pattern), but I thought the persistence
layer and POJOs was supposed to remove this extra layer from the enterprise
application.
3)
If the Order Pojo had some header information an thats all I needed for a
particluar web service request, meaning I do not want the lineitems, should I
create another pojo object mapped to the table but with only the fields that
represent the header? Should I create a Transfer Object/Value Object?
I guess I am some confused of when or if I should use the Pojo when returning
data for remote calls. I have read the J2EE Design Patterns and maybe those
Patterns still apply I just thought that pojos where supposed to take place of
value and transfer objects.
Thanks for any help :)
J
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