EJB 3.0 Stateful session bean shared between Servlet's

Hello
I have a bit of a noob question regarding Stateful sessions beans.
I am wanting to know if there is a way that I can share an instance of a session bean between multiple HttpServlet instances?
I am sending XML messages from a mobile J2ME application, there will be several http POST's made from the mobile client to the server. I would like these multiple POST's to be passed from the handling servlet instance to the same uniquely identified single stateful session bean instance (i can then @Remove the stateful bean when I have finished my several requests).
I would greatly appreciate any tips anyone could give me.

If not, your only option is to maintain the
association yourself by creating a unique id for
each
conversation and storing that id along with the SFSB
reference in the ServletContext. Then you'll
need to pass the id in along with each invocation to
retrieve the appropriate SFSB reference.Thanks for your reply.
Will I always be presented with the same ServletContext instance? Even if the time between requests might be many minutes? Where can I learn more about how to use the ServletContext?
Thanks!

Similar Messages

How create EJB 2.1 Stateful Session Bean in a EJB 3.0 Session Bean

Hi All,
We have been developing on EJB 2.1. We are now adding a module on EJB 3.0.
How can we "create" a stateful session bean with create method signature similar to create(String id)?
We have tried
// this is the remote interface
@EJB AddressBean abean;
But not working
Any help will be appreciated.

There is no explicit create() call for EJB 3.0 session beans. It doesn't really matter though
since you can accomplish the same thing by defining your own business method to act
as an initializer for whatever state you'd like. E.g.
@Remote
public interface FooInterface {
public void initialize(String id);
// ... other business methods
@EJB FooInterface fooRef;
fooRef.initialize("foo");
--ken

SAME EJB 3.0 Stateful Session bean for different JSP sessions returned

Forum,
I have a strange problem utilizing stateful session beans. Please note, that I am using jdeveloper for the following:
1) Here is a basic stateful session bean:
@Stateful(name = "DemoClass")
public class DemoClassBean implements DemoClass,
           DemoClassLocal, SessionSynchronization {
      public static int id=0;
      public DemoClassBean() {
      id++;
      public int getId() {
         return id;
      //... other methods
}2) This bean is accessed from a JSP for testing purpose, I am copying only the script used in JSP:
<%
   DemoClass bean = null;
   try {
      bean = (DemoClass) ((new javax.naming.InitialContext()).
                   lookup("DemoClass "));
      System.out.println("ID=" + bean.getId() );
      } catch (javax.naming.NamingException e) {
         // TODO
%>If this page is addressed by different clients, from different browsers, the same bean is returned.
Here is what I see in the logs:
ID=1
ID=1
ID=1
The same problem is being observed when this session bean is accessed from a JSF Backing bean.
What could be wrong? Is this a bug in oc4j / jdeveloper (version 10.1.3.3.0)?
Edited by: smw000000001 on Nov 17, 2008 10:52 AM

Hi,
The code for stateful is perfectly fine and working in a normal way. The way you are trying to implement the stateful session bean in your application is wrong.
think of binding the stateful session bean with HttpSession object.
So that you will get a unique stateful session bean object.

EJB 2.0 STATEFUL SESSION BEANS -- ejbPassivate or ejbActivate is not called

Hi,
am using Oracle Jdevloper 9i. When i use Stateful Session beans the ejbPassivate or ejbActivated methods are not being called. What is the reason?

Hi Arun,
The decision of when to passivate a stateful session bean is up to a particular vendor's implementation. Typically each vendor will have some configuration that controls this decision, but it's certainly common for passivation to not take place for a given workload. Your best bet is to look at the Oracle documentation to see how the container makes its passivation decision.
--ken

Call existing stateful session bean in different servlets

hello,
we are implementing a shopping cart for our online dvd store in netbeans 5.5.1 and ejb 3.0.
for that we use a stateful session bean, which is created when a user is logging in for connecting the user-entity to the bean.
after logging in, the list servlet, which displays a list of all available dvds, is shown. after clicking the "add to shopping cart" button, the cart servlet with a list of all added dvds is shown. in this servlet we want to reactivate the existing stateful session bean. is this possible? and when it's possible, how is it possible? ;)
our sessionbean with initialize() method:
@Stateful
public class CartBean implements Cart {
    UserEntity user;
    List<DVDEntity> contents;
    public void initialize(UserEntity user){
        System.out.println("Warenkorb erstellt");
        this.user = user;
        contents = new ArrayList<DVDEntity>();
}thx!
Edited by: licherpremium on Nov 8, 2007 6:35 AM

hello,
we are implementing a shopping cart for our online dvd store in netbeans 5.5.1 and ejb 3.0.
for that we use a stateful session bean, which is created when a user is logging in for connecting the user-entity to the bean.
after logging in, the list servlet, which displays a list of all available dvds, is shown. after clicking the "add to shopping cart" button, the cart servlet with a list of all added dvds is shown. in this servlet we want to reactivate the existing stateful session bean. is this possible? and when it's possible, how is it possible? ;)
our sessionbean with initialize() method:
@Stateful
public class CartBean implements Cart {
    UserEntity user;
    List<DVDEntity> contents;
    public void initialize(UserEntity user){
        System.out.println("Warenkorb erstellt");
        this.user = user;
        contents = new ArrayList<DVDEntity>();
}thx!
Edited by: licherpremium on Nov 8, 2007 6:35 AM

Passivation of Connection Object in Stateful Session Bean

Hi all,
I am developing a Stateful session bean that has a Connection object as its instance variable. And this bean starts transaction that spans across multiple method calls and finally either commit or rollback.
BeanClass
UserTransaction utx;
Connection conn;
ejbCreate()
allocateconnection();
ejbRemove()
closeconnection();
ejbActivate()
allocateconnection();
ejbpassivate()
closeconnection();
StartTransaction()
utx = getusertransaction();
utx.begin();
Method1()
do something with database
Method2()
do something with database
CommitTransaction()
utx.commit();
For example, the typical usage of this bean would be:
bean.StartTransaction();
bean.Method1();
bean.Method2();
bean.CommitTransaction();
Here are my two questions:
1. General Question: In order for a Connection object to join a Transaction, Do I have to create the connection after the transaction has started?
2. If the answer to the above question is yes, then: I understand that when this bean get passivated, the UserTransaction instance object would be passivated. And since the connection object can't not be passivated, I have to recreate the connection object in ejbactivate() method, would newly created connection participate in the same Transaction that was being passivated and now activated?

>
Hi all,
I am developing a Stateful session bean that has a
Connection object as its instance variable. And this
bean starts transaction that spans across multiple
method calls and finally either commit or rollback.
BeanClass
UserTransaction utx;
Connection conn;
ejbCreate()
allocateconnection();
ejbRemove()
closeconnection();
ejbActivate()
allocateconnection();
ejbpassivate()
closeconnection();
StartTransaction()
utx = getusertransaction();
utx.begin();
Method1()
do something with database
Method2()
do something with database
CommitTransaction()
utx.commit();
For example, the typical usage of this bean would be:
bean.StartTransaction();
bean.Method1();
bean.Method2();
bean.CommitTransaction();
Here are my two questions:
1. General Question: In order for a Connection object
to join a Transaction, Do I have to create the
connection after the transaction has started?Strictly NO. In fact, the connection is obtained first and then can a transaction begin.
2. If the answer to the above question is yes, then: I
understand that when this bean get passivated, the
UserTransaction instance object would be passivated.
And since the connection object can't not be
passivated, I have to recreate the connection object
in ejbactivate() method, would newly created
connection participate in the same Transaction that
was being passivated and now activated?
The answer to first question being NO, your argument for question 2 does not hold true. According to the EJB specification, a stateful session bean can only be passivated between the transaction and not within a transaction. Your implementation for the stateful EJB is good to work.

Stop passivation in stateful session bean

hi
How to stop the passivation in stateful session bean
Regards
Gajendran.G

>
Hi all,
I am developing a Stateful session bean that has a
Connection object as its instance variable. And this
bean starts transaction that spans across multiple
method calls and finally either commit or rollback.
BeanClass
UserTransaction utx;
Connection conn;
ejbCreate()
allocateconnection();
ejbRemove()
closeconnection();
ejbActivate()
allocateconnection();
ejbpassivate()
closeconnection();
StartTransaction()
utx = getusertransaction();
utx.begin();
Method1()
do something with database
Method2()
do something with database
CommitTransaction()
utx.commit();
For example, the typical usage of this bean would be:
bean.StartTransaction();
bean.Method1();
bean.Method2();
bean.CommitTransaction();
Here are my two questions:
1. General Question: In order for a Connection object
to join a Transaction, Do I have to create the
connection after the transaction has started?Strictly NO. In fact, the connection is obtained first and then can a transaction begin.
2. If the answer to the above question is yes, then: I
understand that when this bean get passivated, the
UserTransaction instance object would be passivated.
And since the connection object can't not be
passivated, I have to recreate the connection object
in ejbactivate() method, would newly created
connection participate in the same Transaction that
was being passivated and now activated?
The answer to first question being NO, your argument for question 2 does not hold true. According to the EJB specification, a stateful session bean can only be passivated between the transaction and not within a transaction. Your implementation for the stateful EJB is good to work.

"Sharing" a stateful session bean between two servlets, beans

Hello!
I just started to learn some java ee programming and was wondering how i would share one stateful session bean between two servlets.
I created the bean with @Stateful.
I tried to inject the stateful bean in both servlets by @EJB and i can manipulate the object, but each servlet seems to have its own object.
The bean has a remote interface that it implements.
What i also tried was to add the mappedName to the @Stateful expression. Something like: @Stateful(mappedName="name") and to use the bean by @EJB(mappedName="name") but it had no effect.
Im using glassfish 2.1 with netbeans 6.7.1 as my environment (standard settings)
dummy question, but i googled like hours and couldnt find anything : \
hope someone can help and sorry for my bad english
greets and thanks

Hi there!
I think you are searching for something like an application wide singleton. There is the possibility to define such one in the Glassfish admin console.
Hope this helps!

Creating multiple stateful session beans from a java client. (EJB 3.0)

I'm having difficulties with the following:
To access the ShoppingCartBean, I have to put the following annotation in my standalone java client:
@EJB
private static ShoppingCartRemote shoppingCartBean;
The static must be there, thus only one ShoppingCartBean will exist within my java client. But as the ShoppingCartBean is a stateful session bean, I want to be able to get different beans of the same type.
What is the correct way to do this in EJB 3.0?

Great question. Because Home interfaces have been removed for the EJB 3.0 simplified
API, stateful session bean creation happens as a side-effect of injection. However, the
same is true of EJB 3.0 business interface lookups. The easiest way to create additional
stateful session beans is to lookup the same dependency that was declared via your
@EJB annotation.
E.g.,
// Assuming the declaring class is pkg1.ShoppingCartClient.java
InitialContext ic = new InitialContext();
ShoppingCartRemote scr1 = (ShoppingCartRemote)
ic.lookup("java:comp/env/pkg1.ShoppingCartClient/shoppingCartBean");
Note that the name relative to java:comp/env is the default associated with your
@EJB annotation since the name() attribute wasn't used. Alternatively, you
could have used :
@EJB(name="scb") private static ShoppingCartRemote shoppingCartBean;
InitialContext ic = new InitialContext();
ShoppingCartRemote scr1 = (ShoppingCartRemote) ic.lookup("java:comp/env/scb");
Yet another alternative is to declare the @EJB at the class-level. This just defines
the dependency without any injection, which is fine if you want to create a bunch of
them via lookup anyway.
@EJB(name="scb", beanInterface=ShoppingCartRemote.class)
public class .... {

Stateful Session Bean Initialization (EJB 3.0)

Hi all!
In EJB 2.1 the initialization was with create (args) methods. NOw, how is it exploited? Create methods are no more there and there must be a way to send parameters to the stateful session bean when it is newly created...isn't it?
Thank you!

There is no pre-defined equivalent of a create method in EJB 3.0. If you want to initialize a
stateful session bean, just define a business method that the client should use as an initialization
method.

How to intantiate Stateful session bean in EJB 3 ?

In EJB 2.x, to instantiate a Stateful Session bean the process was:
1. Lookup Home object
2. call create(args) method on Home, that in turn would call corresponding ejbCreate(args) on the bean implementation.
Now, in EJB 3, there is no concept of Home interaface, How can I instantiate a stateful session bean with some initialization parameters.
Thanks

Just the spec. NetBeans should only be providing the ability to add an ejbCreate method if the bean exposes a Local or Remote 2.x view.
Each lookup or injection of a stateful session bean results in a new bean instance. As long as you call your methods to populate the additional
state right after first acquiring the stateful session bean reference it will work.
--ken

What's the difference between the LRU and NRU strategy for stateful session bean?

Hi,
Does anybody know the difference between the LRU and NRU strategy for
stateful session bean?
Thanks,
Levi

LRU makes the assumption that the bean that has been used a lot recently is
likely to be used again.
NRU simply removes the beans that have not been used for a stipulated amount
of time.
The algorithm for the LRU is much more complicated than the NRU. I think BEA
recommends LRU for better performance and NRU when you have memory
constraints.
"levi" <[email protected]> wrote in message
news:[email protected]..
Hi,
Does anybody know the difference between the LRU and NRU strategy for
stateful session bean?
Thanks,
Levi

[EJB] Stateful session bean--- strange error

hi guys,
here s my problem. i m trying to developp a stateful session bean with two ejbcreate method. one with parameters ( ejbcreate(int val)) and another one without (ejbcreate()).
The client can call ejbcreate without any pbs. everything s allright.
but when i try to get a remote access to the bean via a
MY_BEAN.create(5); then i got an error saying :
FAILED TO FIND METHOD FOR HASH ......
i dont understand cuz i checked my files many times and the two methods are implemented and declared in the home interface.
what should i do ?
please.
tery

Hi Tery,
You are in the wrong forum. This forum is for the Sun Java Studio Creator.
Cheers :-)!!!

Accessing the same stateful session bean from multiple clients in a clustered environment

I am trying to access the same stateful session bean from multiple
          clients. I also want this bean to have failover support so we want to
          deploy it in a cluster. The following description is how we have tried
          to solve this problem, but it does not seem to be working. Any
          insight would be greatly appreciated!
          I have set up a cluster of three servers. I deployed a stateful
          session bean with in memory replication across the cluster. A client
          obtains a reference to an instance of one of these beans to handle a
          request. Subsequent requests will have to use the same bean and could
          come from various clients. So after using the bean the first client
          stores the handle to the bean (actually the replica aware stub) to be
          used by other clients to be able to obtain the bean. When another
          client retrieves the handle gets the replica aware stub and makes a
          call to the bean the request seems to unpredictably go to any of the
          three servers rather than the primary server hosting that bean. If the
          call goes to the primary server everything seems to work fine the
          session data is available and it gets backed up on the secondary
          server. If it happens to go to the secondary server a bean that has
          the correct session data services the request but gives the error
          <Failed to update the secondary copy of a stateful session bean from
          home:ejb20-statefulSession-TraderHome>. Then any subsequent requests
          to the primary server will not reflect changes made on the secondary
          and vice versa. If the request happens to go to the third server that
          is not hosting an instance of that bean then the client receives an
          error that the bean was not available. From my understanding I thought
          the replica aware stub would know which server is the primary host for
          that bean and send the request there.
          Thanks in advance,
          Justin


          If 'allow-concurrent-call' does exactly what you need, then you don't have a problem,
          do you?
          Except of course if you switch ejb containers. Oh well.
          Mike
          "FBenvadi" <[email protected]> wrote:
          >I've got the same problem.
          >I understand from you that concurrent access to a stateful session bean
          >is
          >not allowed but there is a
          >token is weblogic-ejb-jar.xml that is called 'allow-concurrent-call'
          >that
          >does exactly what I need.
          >What you mean 'you'll get a surprise when you go to production' ?
          >I need to understand becouse I can still change the design.
          >Thanks Francesco
          >[email protected]
          >
          >"Mike Reiche" <[email protected]> wrote in message
          >news:[email protected]...
          >>
          >> Get the fix immediately from BEA and test it. It would be a shame to
          >wait
          >until
          >> December only to get a fix - that doesn't work.
          >>
          >> As for stateful session bean use - just remember that concurrent access
          >to
          >a stateful
          >> session bean is not allowed. Things will work fine until you go to
          >production
          >> and encounter some real load - then you will get a surprise.
          >>
          >> Mike
          >>
          >> [email protected] (Justin Meyer) wrote:
          >> >I just heard back from WebLogic Tech Support and they have confirmed
          >> >that this is a bug. Here is their reply:
          >> >
          >> >There is some problem in failover of stateful session beans when its
          >> >run from a java client.However, it is fixed now.
          >> >
          >> >The fix will be in SP2 which will be out by december.
          >> >
          >> >
          >> >Mike,
          >> >Thanks for your reply. I do infact believe we are correctly using
          >a
          >> >stateful session bean however it may have been misleading from my
          >> >description of the problem. We are not accessing the bean
          >> >concurrently from 2 different clients. The second client will only
          >> >come into play if the first client fails. In this case we want to
          >be
          >> >able to reacquire the handle to our stateful session bean and call
          >it
          >> >from the secondary client.
          >> >
          >> >
          >> >Justin
          >> >
          >> >"Mike Reiche" <[email protected]> wrote in message
          >news:<[email protected]>...
          >> >> You should be using an entity bean, not a stateful session bean
          >for
          >> >this application.
          >> >>
          >> >> A stateful session bean is intended to be keep state (stateful)
          >for
          >> >the duration
          >> >> of a client's session (session).
          >> >>
          >> >> It is not meant to be shared by different clients - in fact, if
          >you
          >> >attempt to
          >> >> access the same stateful session bean concurrently - it will throw
          >> >an exception.
          >> >>
          >> >> We did your little trick (storing/retrieving handle) with a stateful
          >> >session bean
          >> >> on WLS 5.1 - and it did work properly - not as you describe. Our
          >sfsb's
          >> >were not
          >> >> replicated as yours are.
          >> >>
          >> >> Mike
          >> >>
          >> >> [email protected] (Justin Meyer) wrote:
          >> >> >I am trying to access the same stateful session bean from multiple
          >> >> >clients. I also want this bean to have failover support so we want
          >> >to
          >> >> >deploy it in a cluster. The following description is how we have
          >tried
          >> >> >to solve this problem, but it does not seem to be working. Any
          >> >> >insight would be greatly appreciated!
          >> >> >
          >> >> >I have set up a cluster of three servers. I deployed a stateful
          >> >> >session bean with in memory replication across the cluster. A client
          >> >> >obtains a reference to an instance of one of these beans to handle
          >> >a
          >> >> >request. Subsequent requests will have to use the same bean and
          >could
          >> >> >come from various clients. So after using the bean the first client
          >> >> >stores the handle to the bean (actually the replica aware stub)
          >to
          >> >be
          >> >> >used by other clients to be able to obtain the bean. When another
          >> >> >client retrieves the handle gets the replica aware stub and makes
          >> >a
          >> >> >call to the bean the request seems to unpredictably go to any of
          >the
          >> >> >three servers rather than the primary server hosting that bean.
          >If
          >> >the
          >> >> >call goes to the primary server everything seems to work fine the
          >> >> >session data is available and it gets backed up on the secondary
          >> >> >server. If it happens to go to the secondary server a bean that
          >has
          >> >> >the correct session data services the request but gives the error
          >> >> ><Failed to update the secondary copy of a stateful session bean
          >from
          >> >> >home:ejb20-statefulSession-TraderHome>. Then any subsequent requests
          >> >> >to the primary server will not reflect changes made on the secondary
          >> >> >and vice versa. If the request happens to go to the third server
          >that
          >> >> >is not hosting an instance of that bean then the client receives
          >an
          >> >> >error that the bean was not available. From my understanding I
          >thought
          >> >> >the replica aware stub would know which server is the primary host
          >> >for
          >> >> >that bean and send the request there.
          >> >> >
          >> >> >Thanks in advance,
          >> >> >Justin
          >>
          >
          >

Losing UserTransaction state in Stateful session bean

I have a UserTransaction I wish to begin and commit in different methods of a Stateful session bean. I have 2 methods to test this on the session bean:
public void beginTransaction()
trans = context.getUserTransaction() ;
trans.begin() ;
public void commitTransaction()
trans = context.getUserTransaction() ;
trans.commit() ;
If I call these methods from one Perform method in a Struts action all works fine. If I call the methods in different Struts actions (storing the session bean handle on the HTTPSession in the first for retrieval in the second) the second call fails with the following exception:
java.lang.IllegalStateException: No active Transaction
The state of the transaction on the second call is STATUS_NO_TRANSACTION. I am certain that I have lost no state on the session bean and that using handles gives me the correct bean since I have written some state to test this. Basically something seems to close the transaction between the end of the first Perform method and the beginning of the second (I am of course assuming this is a valid thing to do).
My session bean descriptor has <transaction-type>Bean</transaction-type>, and I am using OC4J.
If anyone can point out what it is I am doing wrong I would be grateful!
James.

Sorry, I have re-checked my code and I believe I found the problem.
I was beginning my transaction inside ejbCreate() and trying to commit/rollback in another method. This works in JBoss 3.2 but does not work in either OC4J or WebLogic 7.
If I begin my transaction in a business method and commit/rollback in another method, everything works fine. (It also seems to work fine in 9.0.3 this way).
So I am not sure whether this is a bug in 9iAS/WLS, or a bug in JBoss, or something that is left "vague" in the J2EE spec. Unfortunately, examples on bean-managed transactions are thin on the ground generally (the usual advice being not to use them, which I definitely agree with!).
If you believe that the behaviour I describe is a bug in 9iAS, I can send a simple EJB test case.
Keith

EJB 3.0 Stateful session bean shared between Servlet's

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