2

I've just tried to add session listeners in my test web app the HttpSessionBindingListener and HttpSessionAttributeListener ones; They both implemented into my test object as : 

public class MySessionListener implements HttpSessionBindingListener,HttpSessionAttributeListener 
{
//implemented methods...
}

The thing is...

I tried code like a

session.setAttribute("name",new TestValue());

as a result, I expected to call HttpSessionBindingListener event like valueBound(...) but I have called just the HttpSessionAttributeListener one as attributeAdded(...) only :(

Moreover, concerning the valueUnbound(...) method attitude is totally the same thing as I mentioned for I use code like

session.removeAttribute("name");

...but I get all the same attributeRemoved(...) being called only :S

I wanted to try putValue() method instead but right now I am watching HttpSession docs which says that "putValue is Deprecated. As of Version 2.2, this method is replaced by setAttribute(java.lang.String, java.lang.Object)"

So I don't get it why the valueBound(...) or valueUnbound(...) doesn't invoke and how to invoke them anyway?

Thanks

user592704
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1 Answers1

7

Short answer

valueBound is not being called because MySessionListener is not the object being added to a session.

If TestValue implemented HttpSessionBindingListener it's valueBound method would be called.

Longer Explanation

HttpSessionBindingListener is used to notify the object that it is being added to a session.

HttpSessionAttributeListener is used (as you discovered) for attributes being added/removed from a session.

With the HttpSessionBindingListener here is what the container is saying: "Hey TestValue, you were added to a session"

With the HttpSessionAttributeListener here is what the container is saying: "Hey MySessionListener, an attribute was added to a session"

So, if TestValue implements HttpSessionBindingListener, it would have valueBound called when added to a session:

session.setAttribute("name",new TestValue());

In your case, if you added an instance of MySessionListener to a session (not that you'd want to, but because it implements HttpSessionBindingListener) it would call the valueBound method when added to a session:

session.setAttribute("name", new MySessionListener());

Also see: Practical Usage of HttpSessionBindingListener And HttpSessionAttributeListener

Community
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Amir T
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  • Thanks. But as for my case I don't get it "how to add directly to session itself" because I cannot see (in its docs - http://docs.oracle.com/javaee/5/api/javax/servlet/http/HttpSession.html) any related "add" method except the addAttribute(...) one :S You mean the putValue(...,...) method which is deprecated? – user592704 Oct 10 '13 at 17:22
  • setAttribute will trigger valueBound, removeAttribute (or expiration of the session) will trigger valueUnbound. – Amir T Oct 10 '13 at 17:28
  • "Will trigger" ? What you mean? You mean they are chained and synchronized or something? Give more details please because I don't get it should I use putValue(...,...) instead of setAttribute(...,...) – user592704 Oct 10 '13 at 17:34
  • By "Will trigger", I mean "will cause" because by implementing that interface it is the containers job to notify the object. putValue (as you indicated) is deprecated so you should use setAttribute which will add the object to the session. – Amir T Oct 10 '13 at 17:36
  • Yeah. So I did. But I have HttpSessionAttributeListener methods working only :( But why? – user592704 Oct 10 '13 at 17:43
  • It doesn't make sense to implement both interfaces on one object - do you understand the difference between the two interfaces (one is for the object being added, the other is for an external listener)? If you want valueBound to be called, it has to be the object that is being bound to the session. – Amir T Oct 10 '13 at 17:51
  • let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/39005/discussion-between-amir-t-and-user592704) – Amir T Oct 10 '13 at 18:13