Dan,
>Specifically, the EJB Container is not allowed to pass
>non-remote objects
>by reference on inter-EJB invocations when the calling and called
>enterprise beans are collocated in the same JVM. Doing so
>could result in
>the multiple beans sharing the state of a Java object, which
>would break
>the enterprise beans semantics.
Thank for the spec outline Dan.
But, most of the AS do not duplicate the objects passed by reference by
the middleware during a local call, which break the EJB semantic.
That's mean that when you develop an EJB, you must be aware about
problem, and keep in mind that pass-by-value objects may be in fact passed
by references in the case of a local call.
So the following code is dangerous:
public void doSomeStuff(List list) {
list.add("hello");
// do some stuff with "list"
}
This code should be fixed as:
public void doSomeStuff(List list) {
List local = new ArrayList();
Collections.copy(list, local);
local.add("hello");
// do some stuff with "local" }
This example applied as well to by-values returned objects:
private List accounts;
public List getAccounts() {
return accounts;
}
This client may change the account list if the case of a local call
(passed by reference), which break the encapsulation.
This method should be fixed as:
private List accounts;
public List getAccounts() {
List copy = new ArrayList();
Collections.copy(accounts, copy);
return copy;
}
Or (better solution)
private List accounts;
public List getAccounts() {
return Collection.unmodifiableList(accounts);
}
Tibo.
===========================================================================
To unsubscribe, send email to [EMAIL PROTECTED] and include in the body
of the message "signoff EJB-INTEREST". For general help, send email to
[EMAIL PROTECTED] and include in the body of the message "help".
