Another idea is that every time they add do @DependsOn, we could check
for circular references and tell the user they've just created a
circular reference. Being able to determine where circular references
start is impossible unless you were there when it was created, but we
are there and can say with precision "that's the one that did it."
-David
On Aug 7, 2008, at 3:09 PM, Jonathan Gallimore wrote:
I think you're right, it could be pretty hairy. We could traverse
the call hierarchy as I've mentioned in a reply to Karan's mail.
Incidentally, the false-positive case you mention with the if
statement - would it be a problem adding the @DependsOn annotation
in this case? Although that code would never get executed,
technically we are referring to the other singleton.
I'll have a play about with some JDT code over the next few days and
try and get a better idea of what's involved.
Jon
Dain Sundstrom wrote:
It's not that hard to write some ASM code to detect that simple
kind of usage, but more complex usage would be difficult to
impossible. For example:
@PostConstruct
public void startup() {
initBlue();
}
private void initBlue() {
blue.doSomeWork();
}
Now imagine how complex you can make that code and you quickly come
to the conclusion that it is almost impossible to detect reliably.
Of course if you are only interested somewhat accurate results, you
could use a simple detect algorithm, but you will miss some usages
and get some false positives (for example if (false)
blue.doSomeWork()).
-dain
On Aug 7, 2008, at 12:57 PM, David Blevins wrote:
Along those lines what would be really cool is if the tool could
add the @DependsOn automatically for a user.
A singleton needs a @DependsOn declaration only when referring to
(invoking) another singleton in either its @PostConstruct or
@PreDestroy method. I don't know if it's possible, but if there
was some way spot that and add the @DependsOn for them, that'd be
really cool.
As an example, the bean has this:
@Singleton
@Startup
public class RedBean {
@EJB(beanName="BlueBean")
private BlueLocal blue
@PostConstruct
public void startup() {
}
}
and all is fine, but when they add this to the @PostConstruct
method...
@PostConstruct
public void startup() {
blue.doSomeWork();
}
At that point you need to add the @DependsOn like so:
@Singleton
@Startup
@DependsOn("BlueBean")
public class RedBean {
...
}
Don't know if that's possible, but would be cool.
-David
