RE: Concurrent calls to Session bean methods
Hello All,
Thanks very much for all the help you have provided for this query.
I looked into the Java pet store class which you had referred me to.
And have also implemented a facade class.
Here is an example of what our application looks like.
There is an MDB called MyMDB, a stateful session bean called
MyStatefulSessionBean and a facade class called MyFacade
MyMDB.java
---
public class MyMDB extends java.lang.Object implements
javax.ejb.MessageDrivenBean, javax.jms.MessageListener {
static m_myFacade;
private _createFacade()
{
// Creates Facade class
// Initializes myStatefulSessionBean variable in the Facade class
}
public void onMessage(javax.jms.Message message)
{
if( message is init_message )
{
_createFacade();
}
m_myFacade.processMessage( message );
}
}
MyStatefulSessionBean.java
---
public class MyStatefulSessionBean extends java.lang.Object implements
javax.ejb.SessionBean
{
public void processMessage( Message message );
}
MyFacade.java
-
public class MyFacade extends Object
{
MyStatefulSessionBean m_myStatefulSessionBean;
public synchronized void processMessage( Message message )
{
myStatefulSessionBean.processMessage();
}
}
But when the application runs, and sends an init message to MyQueue ( with
which the MDB is accociated ), the onMessage() of MDB gets called. And the
processMessage() gets called and facade class is initialized. The system
behaves in the way it is expected to.
Then, if MyQueue recieves another message, the system still beahves fine by
calling processMessage().
The problem occurs if MyQueue gets more than one messages ( from more than
one threads ). The control comes into onMessage() everytime. Unfortunately,
m_myFacade.processMessage( message ) doesn't get in all the cases. I don't
know if this is a problem with synchronization or may be I am doing
something wrong here. Please somebody help.
Thanks,
Vani
From: The elephantwalker [EMAIL PROTECTED]
Reply-To: Orion-Interest [EMAIL PROTECTED]
To: Orion-Interest [EMAIL PROTECTED]
Subject: RE: Concurrent calls to Session bean methods
Date: Thu, 21 Mar 2002 21:37:55 -0800
The sfsb has a _session_ which is bound to the client. So the client could
be anywhere, irregardless of a cluster.
oc4j has a last method state replication which makes sure that all sfsb's
have the same _session_.
A slsb wouldn't care, and doesn't have the same problem with concurrency,
since they are not reentrant.
regards,
the elephantwalker
-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Romen Law
Sent: Thursday, March 21, 2002 2:33 PM
To: Orion-Interest
Subject: Re: Concurrent calls to Session bean methods
ello,
What if the application is deployed in a cluster (even the web tier)? Would
that nullify the synchronised effect?
cheers
romen
- Original Message -
From: The elephantwalker [EMAIL PROTECTED]
To: Orion-Interest [EMAIL PROTECTED]
Sent: Thursday, March 21, 2002 3:47 PM
Subject: RE: Concurrent calls to Session bean methods
John,
Here is the offending class, compliments of the Sun Blueprint team:
public class ShoppingClientControllerWebImpl implements
WebClientController
{
private ShoppingClientControllerLocal sccEjb;
private HttpSession session;
public ShoppingClientControllerWebImpl() {
}
// ... stuff...
//
// the important bit ...
public synchronized EventResponse handleEvent(Event ev)
throws EventException {
return sccEjb.processEvent(ev);
}
}
So you see that the webcontroller is the _only_ access to the sfsb. And
the
only call is synchronized, thus preventing cocurrent calls to the
stateful
session bean.
regards,
the elephantwalker
www.elephantwalker.com
-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of
[EMAIL PROTECTED]
Sent: Wednesday, March 20, 2002 12:05 PM
To: Orion-Interest
Subject: RE: Concurrent calls to Session bean methods
I haven't seen the history on this issue, but it interests me. I had a
quick look at the ShoppingClientControllerEJB class that is given as an
example by Sun in the Session Facade design pattern, but couldn't see
where
they are synchronizing calls. Can you provide some more clues?
Thanks,
John H.
The elephantwalker
[EMAIL PROTECTED] To:
[EMAIL PROTECTED]
Sent by: cc:
owner-orion-interest@orion Subject: RE:
Concurrent calls to Session bean methods
server.com
03/19/02 10:31 PM
RE: Concurrent calls to Session bean methods
I was also wondering about this. Of course since the webcontroller is not an
EJB it is allowed to use the otherwise banned synchronized keyword!
Guy.
-Original Message-
From: The elephantwalker [mailto:[EMAIL PROTECTED]]
Sent: 21 March 2002 04:48
To: Orion-Interest
Subject: RE: Concurrent calls to Session bean methods
John,
Here is the offending class, compliments of the Sun Blueprint team:
public class ShoppingClientControllerWebImpl implements
WebClientController
{
private ShoppingClientControllerLocal sccEjb;
private HttpSession session;
public ShoppingClientControllerWebImpl() {
}
// ... stuff...
//
// the important bit ...
public synchronized EventResponse handleEvent(Event ev)
throws EventException {
return sccEjb.processEvent(ev);
}
}
So you see that the webcontroller is the _only_ access to the
sfsb. And the
only call is synchronized, thus preventing cocurrent calls to
the stateful
session bean.
regards,
the elephantwalker
www.elephantwalker.com
-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of
[EMAIL PROTECTED]
Sent: Wednesday, March 20, 2002 12:05 PM
To: Orion-Interest
Subject: RE: Concurrent calls to Session bean methods
I haven't seen the history on this issue, but it interests
me. I had a
quick look at the ShoppingClientControllerEJB class that is
given as an
example by Sun in the Session Facade design pattern, but
couldn't see where
they are synchronizing calls. Can you provide some more clues?
Thanks,
John H.
The elephantwalker
[EMAIL PROTECTED] To:
[EMAIL PROTECTED]
Sent by: cc:
owner-orion-interest@orion Subject: RE:
Concurrent calls to Session bean methods
server.com
03/19/02 10:31 PM
Please respond to
Orion-Interest
Vani,
You can use the petstore trick. Use a facade class which
sychronizes each
call to your session bean. That should do the trick.
This is a _famous_ problem with session beans.
regards,
the elephantwalker
www.elephantwalker.com
-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Vani H.S.
Sent: Wednesday, March 20, 2002 12:04 AM
To: Orion-Interest
Subject: Concurrent calls to Session bean methods
Hello All,
I have been trying to deploy an application consisting of
session beans
and mdbs onto orion1.5.4.
But I seem to run into deadlocks, because my session bean
gets called
concurrently. Please can anybody can tell me if there is a
setting to allow
concurrent calls so that, when a session bean method is
called at one time,
the EJB container blocks the concurrent method call and allows it to
proceed
when the previous call has completed?
If not, how should this problem of concurrent calls be
handled in orion?
Please help.
Thanks,
Vani
The allow-concurrent-calls element specifies whether a
stateful session
bean
instance allows concurrent method calls. By default,
allows-concurrent-calls
is false. However, when this value is set to true, the EJB
container blocks
the concurrent method call and allows it to proceed when the
previous call
has completed.
_
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Re: Concurrent calls to Session bean methods
there is a controller webimpl that acts as a facade, and that method is synchronized... [EMAIL PROTECTED] wrote: I haven't seen the history on this issue, but it interests me. I had a quick look at the ShoppingClientControllerEJB class that is given as an example by Sun in the Session Facade design pattern, but couldn't see where they are synchronizing calls. Can you provide some more clues? Thanks, John H. The elephantwalker [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent by: cc: owner-orion-interest@orion Subject: RE: Concurrent calls to Session bean methods server.com 03/19/02 10:31 PM Please respond to Orion-Interest Vani, You can use the petstore trick. Use a facade class which sychronizes each call to your session bean. That should do the trick. This is a _famous_ problem with session beans. regards, the elephantwalker www.elephantwalker.com -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Vani H.S. Sent: Wednesday, March 20, 2002 12:04 AM To: Orion-Interest Subject: Concurrent calls to Session bean methods Hello All, I have been trying to deploy an application consisting of session beans and mdbs onto orion1.5.4. But I seem to run into deadlocks, because my session bean gets called concurrently. Please can anybody can tell me if there is a setting to allow concurrent calls so that, when a session bean method is called at one time, the EJB container blocks the concurrent method call and allows it to proceed when the previous call has completed? If not, how should this problem of concurrent calls be handled in orion? Please help. Thanks, Vani The allow-concurrent-calls element specifies whether a stateful session bean instance allows concurrent method calls. By default, allows-concurrent-calls is false. However, when this value is set to true, the EJB container blocks the concurrent method call and allows it to proceed when the previous call has completed. _ Join the world's largest e-mail service with MSN Hotmail. http://www.hotmail.com
Re: Concurrent calls to Session bean methods
ello,
What if the application is deployed in a cluster (even the web tier)? Would
that nullify the synchronised effect?
cheers
romen
- Original Message -
From: The elephantwalker [EMAIL PROTECTED]
To: Orion-Interest [EMAIL PROTECTED]
Sent: Thursday, March 21, 2002 3:47 PM
Subject: RE: Concurrent calls to Session bean methods
John,
Here is the offending class, compliments of the Sun Blueprint team:
public class ShoppingClientControllerWebImpl implements
WebClientController
{
private ShoppingClientControllerLocal sccEjb;
private HttpSession session;
public ShoppingClientControllerWebImpl() {
}
// ... stuff...
//
// the important bit ...
public synchronized EventResponse handleEvent(Event ev)
throws EventException {
return sccEjb.processEvent(ev);
}
}
So you see that the webcontroller is the _only_ access to the sfsb. And
the
only call is synchronized, thus preventing cocurrent calls to the stateful
session bean.
regards,
the elephantwalker
www.elephantwalker.com
-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of
[EMAIL PROTECTED]
Sent: Wednesday, March 20, 2002 12:05 PM
To: Orion-Interest
Subject: RE: Concurrent calls to Session bean methods
I haven't seen the history on this issue, but it interests me. I had a
quick look at the ShoppingClientControllerEJB class that is given as an
example by Sun in the Session Facade design pattern, but couldn't see
where
they are synchronizing calls. Can you provide some more clues?
Thanks,
John H.
The elephantwalker
[EMAIL PROTECTED] To:
[EMAIL PROTECTED]
Sent by: cc:
owner-orion-interest@orion Subject: RE:
Concurrent calls to Session bean methods
server.com
03/19/02 10:31 PM
Please respond to
Orion-Interest
Vani,
You can use the petstore trick. Use a facade class which sychronizes each
call to your session bean. That should do the trick.
This is a _famous_ problem with session beans.
regards,
the elephantwalker
www.elephantwalker.com
-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Vani H.S.
Sent: Wednesday, March 20, 2002 12:04 AM
To: Orion-Interest
Subject: Concurrent calls to Session bean methods
Hello All,
I have been trying to deploy an application consisting of session beans
and mdbs onto orion1.5.4.
But I seem to run into deadlocks, because my session bean gets called
concurrently. Please can anybody can tell me if there is a setting to
allow
concurrent calls so that, when a session bean method is called at one
time,
the EJB container blocks the concurrent method call and allows it to
proceed
when the previous call has completed?
If not, how should this problem of concurrent calls be handled in orion?
Please help.
Thanks,
Vani
The allow-concurrent-calls element specifies whether a stateful session
bean
instance allows concurrent method calls. By default,
allows-concurrent-calls
is false. However, when this value is set to true, the EJB container
blocks
the concurrent method call and allows it to proceed when the previous call
has completed.
_
Join the world's largest e-mail service with MSN Hotmail.
http://www.hotmail.com
RE: Concurrent calls to Session bean methods
The sfsb has a _session_ which is bound to the client. So the client could
be anywhere, irregardless of a cluster.
oc4j has a last method state replication which makes sure that all sfsb's
have the same _session_.
A slsb wouldn't care, and doesn't have the same problem with concurrency,
since they are not reentrant.
regards,
the elephantwalker
-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Romen Law
Sent: Thursday, March 21, 2002 2:33 PM
To: Orion-Interest
Subject: Re: Concurrent calls to Session bean methods
ello,
What if the application is deployed in a cluster (even the web tier)? Would
that nullify the synchronised effect?
cheers
romen
- Original Message -
From: The elephantwalker [EMAIL PROTECTED]
To: Orion-Interest [EMAIL PROTECTED]
Sent: Thursday, March 21, 2002 3:47 PM
Subject: RE: Concurrent calls to Session bean methods
John,
Here is the offending class, compliments of the Sun Blueprint team:
public class ShoppingClientControllerWebImpl implements
WebClientController
{
private ShoppingClientControllerLocal sccEjb;
private HttpSession session;
public ShoppingClientControllerWebImpl() {
}
// ... stuff...
//
// the important bit ...
public synchronized EventResponse handleEvent(Event ev)
throws EventException {
return sccEjb.processEvent(ev);
}
}
So you see that the webcontroller is the _only_ access to the sfsb. And
the
only call is synchronized, thus preventing cocurrent calls to the stateful
session bean.
regards,
the elephantwalker
www.elephantwalker.com
-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of
[EMAIL PROTECTED]
Sent: Wednesday, March 20, 2002 12:05 PM
To: Orion-Interest
Subject: RE: Concurrent calls to Session bean methods
I haven't seen the history on this issue, but it interests me. I had a
quick look at the ShoppingClientControllerEJB class that is given as an
example by Sun in the Session Facade design pattern, but couldn't see
where
they are synchronizing calls. Can you provide some more clues?
Thanks,
John H.
The elephantwalker
[EMAIL PROTECTED] To:
[EMAIL PROTECTED]
Sent by: cc:
owner-orion-interest@orion Subject: RE:
Concurrent calls to Session bean methods
server.com
03/19/02 10:31 PM
Please respond to
Orion-Interest
Vani,
You can use the petstore trick. Use a facade class which sychronizes each
call to your session bean. That should do the trick.
This is a _famous_ problem with session beans.
regards,
the elephantwalker
www.elephantwalker.com
-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Vani H.S.
Sent: Wednesday, March 20, 2002 12:04 AM
To: Orion-Interest
Subject: Concurrent calls to Session bean methods
Hello All,
I have been trying to deploy an application consisting of session beans
and mdbs onto orion1.5.4.
But I seem to run into deadlocks, because my session bean gets called
concurrently. Please can anybody can tell me if there is a setting to
allow
concurrent calls so that, when a session bean method is called at one
time,
the EJB container blocks the concurrent method call and allows it to
proceed
when the previous call has completed?
If not, how should this problem of concurrent calls be handled in orion?
Please help.
Thanks,
Vani
The allow-concurrent-calls element specifies whether a stateful session
bean
instance allows concurrent method calls. By default,
allows-concurrent-calls
is false. However, when this value is set to true, the EJB container
blocks
the concurrent method call and allows it to proceed when the previous call
has completed.
_
Join the world's largest e-mail service with MSN Hotmail.
http://www.hotmail.com
RE: Concurrent calls to Session bean methods
I haven't seen the history on this issue, but it interests me. I had a quick look at the ShoppingClientControllerEJB class that is given as an example by Sun in the Session Facade design pattern, but couldn't see where they are synchronizing calls. Can you provide some more clues? Thanks, John H. The elephantwalker [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent by: cc: owner-orion-interest@orion Subject: RE: Concurrent calls to Session bean methods server.com 03/19/02 10:31 PM Please respond to Orion-Interest Vani, You can use the petstore trick. Use a facade class which sychronizes each call to your session bean. That should do the trick. This is a _famous_ problem with session beans. regards, the elephantwalker www.elephantwalker.com -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Vani H.S. Sent: Wednesday, March 20, 2002 12:04 AM To: Orion-Interest Subject: Concurrent calls to Session bean methods Hello All, I have been trying to deploy an application consisting of session beans and mdbs onto orion1.5.4. But I seem to run into deadlocks, because my session bean gets called concurrently. Please can anybody can tell me if there is a setting to allow concurrent calls so that, when a session bean method is called at one time, the EJB container blocks the concurrent method call and allows it to proceed when the previous call has completed? If not, how should this problem of concurrent calls be handled in orion? Please help. Thanks, Vani The allow-concurrent-calls element specifies whether a stateful session bean instance allows concurrent method calls. By default, allows-concurrent-calls is false. However, when this value is set to true, the EJB container blocks the concurrent method call and allows it to proceed when the previous call has completed. _ Join the world's largest e-mail service with MSN Hotmail. http://www.hotmail.com
RE: Concurrent calls to Session bean methods
Thanks for the suggestion, Elephantwalker. Will look into the facade class used in pet store application. Regards, Vani From: The elephantwalker [EMAIL PROTECTED] Reply-To: Orion-Interest [EMAIL PROTECTED] To: Orion-Interest [EMAIL PROTECTED] Subject: RE: Concurrent calls to Session bean methods Date: Tue, 19 Mar 2002 20:31:38 -0800 Vani, You can use the petstore trick. Use a facade class which sychronizes each call to your session bean. That should do the trick. This is a _famous_ problem with session beans. regards, the elephantwalker www.elephantwalker.com -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Vani H.S. Sent: Wednesday, March 20, 2002 12:04 AM To: Orion-Interest Subject: Concurrent calls to Session bean methods Hello All, I have been trying to deploy an application consisting of session beans and mdbs onto orion1.5.4. But I seem to run into deadlocks, because my session bean gets called concurrently. Please can anybody can tell me if there is a setting to allow concurrent calls so that, when a session bean method is called at one time, the EJB container blocks the concurrent method call and allows it to proceed when the previous call has completed? If not, how should this problem of concurrent calls be handled in orion? Please help. Thanks, Vani The allow-concurrent-calls element specifies whether a stateful session bean instance allows concurrent method calls. By default, allows-concurrent-calls is false. However, when this value is set to true, the EJB container blocks the concurrent method call and allows it to proceed when the previous call has completed. _ Join the worlds largest e-mail service with MSN Hotmail. http://www.hotmail.com _ Chat with friends online, try MSN Messenger: http://messenger.msn.com
RE: Concurrent calls to Session bean methods
John,
Here is the offending class, compliments of the Sun Blueprint team:
public class ShoppingClientControllerWebImpl implements WebClientController
{
private ShoppingClientControllerLocal sccEjb;
private HttpSession session;
public ShoppingClientControllerWebImpl() {
}
// ... stuff...
//
// the important bit ...
public synchronized EventResponse handleEvent(Event ev)
throws EventException {
return sccEjb.processEvent(ev);
}
}
So you see that the webcontroller is the _only_ access to the sfsb. And the
only call is synchronized, thus preventing cocurrent calls to the stateful
session bean.
regards,
the elephantwalker
www.elephantwalker.com
-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of
[EMAIL PROTECTED]
Sent: Wednesday, March 20, 2002 12:05 PM
To: Orion-Interest
Subject: RE: Concurrent calls to Session bean methods
I haven't seen the history on this issue, but it interests me. I had a
quick look at the ShoppingClientControllerEJB class that is given as an
example by Sun in the Session Facade design pattern, but couldn't see where
they are synchronizing calls. Can you provide some more clues?
Thanks,
John H.
The elephantwalker
[EMAIL PROTECTED] To:
[EMAIL PROTECTED]
Sent by: cc:
owner-orion-interest@orion Subject: RE:
Concurrent calls to Session bean methods
server.com
03/19/02 10:31 PM
Please respond to
Orion-Interest
Vani,
You can use the petstore trick. Use a facade class which sychronizes each
call to your session bean. That should do the trick.
This is a _famous_ problem with session beans.
regards,
the elephantwalker
www.elephantwalker.com
-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Vani H.S.
Sent: Wednesday, March 20, 2002 12:04 AM
To: Orion-Interest
Subject: Concurrent calls to Session bean methods
Hello All,
I have been trying to deploy an application consisting of session beans
and mdbs onto orion1.5.4.
But I seem to run into deadlocks, because my session bean gets called
concurrently. Please can anybody can tell me if there is a setting to allow
concurrent calls so that, when a session bean method is called at one time,
the EJB container blocks the concurrent method call and allows it to
proceed
when the previous call has completed?
If not, how should this problem of concurrent calls be handled in orion?
Please help.
Thanks,
Vani
The allow-concurrent-calls element specifies whether a stateful session
bean
instance allows concurrent method calls. By default,
allows-concurrent-calls
is false. However, when this value is set to true, the EJB container blocks
the concurrent method call and allows it to proceed when the previous call
has completed.
_
Join the world's largest e-mail service with MSN Hotmail.
http://www.hotmail.com
RE: Concurrent calls to Session bean methods
Vani, You can use the petstore trick. Use a facade class which sychronizes each call to your session bean. That should do the trick. This is a _famous_ problem with session beans. regards, the elephantwalker www.elephantwalker.com -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Vani H.S. Sent: Wednesday, March 20, 2002 12:04 AM To: Orion-Interest Subject: Concurrent calls to Session bean methods Hello All, I have been trying to deploy an application consisting of session beans and mdbs onto orion1.5.4. But I seem to run into deadlocks, because my session bean gets called concurrently. Please can anybody can tell me if there is a setting to allow concurrent calls so that, when a session bean method is called at one time, the EJB container blocks the concurrent method call and allows it to proceed when the previous call has completed? If not, how should this problem of concurrent calls be handled in orion? Please help. Thanks, Vani The allow-concurrent-calls element specifies whether a stateful session bean instance allows concurrent method calls. By default, allows-concurrent-calls is false. However, when this value is set to true, the EJB container blocks the concurrent method call and allows it to proceed when the previous call has completed. _ Join the worlds largest e-mail service with MSN Hotmail. http://www.hotmail.com
