How Stateless Session Bean instances in pool

Hi,
I am not clear about , stateless bean having "pool" of objects to be used by multiple clients.when those instances will be created or who will generate them.
Is this pool specific to ejb container or any vendor container.
thanks in advance,

Hi , my question is about Stateless Session Bean ,
how StatelessSession bean will behave when some 100
clients wil call homeObject simultaneously.The EJBs(including stateless) are single threaded so one client can access one Bean at a time. As per your question if some 100 clients are invoking home.create() method then it has to invoke on 100 EJBs. The instance pool size can be specified while deploying. In the descriptor (application server speific). So if the number of simultaneous clients is more than the pool size then some clients have to wait.
Now my second question is how and who will create
these instance .The container will create the pool as per the application server spcific deployment descriptor.

Similar Messages

Singleton stateless session bean

hello
how to implement "singleton stateless session bean"?
thanks in advance!!

This is a case of premature optimization. Try forgetting about how to solve a singleton problem for the time being. Focus on the use-cases of your application and getting something working.
After that, if memory usage continues to be an issue, consider the following. If you have a large amount of data needed by multiple clients, one option to store it in a database and retrieve portions on demand. If you need to keep everything in memory in each bean instance you can also configure the total number of stateless session bean instances in your vendor's bean pool to limit the total resource usage. A third alternative is to use a third-party caching implementation or a vendor-specific singleton service.
--ken

Number of Instances of Stateless Session Bean

For a servlet(not SingleThreadModel) not hosted in a distributed environment(the default),the servlet container must use only one instance per servlet declaration.
All instances of a stateless session bean are equivalent.
In this case, why do the EJB container need to create more than one instances per stateless session bean?
thanks.

Would you like to explain why a servlet declaration
has only one instance?Handling the different client requests as separate threads in the service() method of the servlet is more efficient than using a pool of servlets. That's one of the reasons that the SingleThreadModel (usually implemented using a pool) is now deprecated, along with the fact that that model gives the developer a false sense of security as to multithreading issues...
Once we leave the Web tier to handle remote objects (EJBs) or database connections, we have a different problem, since we are faced with objects that are slow to create and tie up much more resources. In the biz and back-end tiers, using a pool of already existing instances gives actually better performance.

How to use jta in toplink and stateless session bean EJB 3.0?

I have an application with techologies jsf,stateless session bean, adf, toplink
generated by toplink workbench.
In web side ı want to use two methods in stateless session bean which are updated
different tables. I call these methods in my page backing bean.
I also want to JTA in web side. My first methods is done correctly, but second method has an error. I wanto to rollback all transaction.
How can ı do that? with using JTA in Toplink...

Yuichi
Did you manage to solve this? I'm doing something similar and seeing the same problem, although they're up to 7.3 SP7.
Any help greatly appreciated.
Lewis

How to get stateful and stateless session bean in second jsp

I create stateful session bean in the first jsp, then how can I get the stateful session bean in the second jsp? I find that somebody store the bean in HttpSession.
If I store the stateful session bean in HttpSession, then I can get it in the second jsp. My problem is that I can store the stateless session bean in HttpSession, and get it in the second jsp. Then, both stateful and stateless can maintain the state in the second jsp. What is the difference between stateful and stateless session bean in this case ?
I understand the definition of stateful and stateless session bean, but I'm confuse how to use session bean. Can anyone provide sample jsp to show difference of stateful and stateless? How the stateful session bean can maintain the state for the client?

Greetings,
I create stateful session bean in the first jsp, then how can I get the stateful session bean in the
second jsp? I find that somebody store the bean in HttpSession.Which is the correct scope for sharing client-specific data when 'request' scope is insufficient.
If I store the stateful session bean in HttpSession, then I can get it in the second jsp. My problem is
that I can store the stateless session bean in HttpSession, and get it in the second jsp. Then, bothWhy is that a "problem"? Does your application not require the stateless bean to be shared? If so, then don't store the EJBObject reference in the session...
stateful and stateless can maintain the state in the second jsp. What is the difference betweenWhat do you mean by this exactly?..
stateful and stateless session bean in this case ?Statefulness of session beans is in regard to maintaining client state (er, in all cases). If your "stateless" bean is receiving information from the client (i.e. its caller) - either through a create method or a business method - and that information is available (retrievable from the bean) on subsequent method calls, then that bean is, in fact, stateful - regardless of how it is deployed.
I understand the definition of stateful and stateless session bean, but I'm confuse how to use
session bean.The correct question, it here seems, is "when" to use which type... Use a "stateful" bean when information about (from) the client (i.e. the caller) must be maintained across method calls of the bean. Use a "stateless" bean for general business methods that do not depend on "prior knowledge" of the client (i.e. the caller).
Can anyone provide sample jsp to show difference of stateful and stateless? How the statefulA "sample JSP" would yield nothing additional... The semantics of calling, using, and "persisting", bean references are always the same - regardless of type or class. However, the reason(s) for using one over the other depends entirely on the needs of your application.
session bean can maintain the state for the client?I recommend that you spend more time learning about EJBs generally. In particular, it seems you require more fundamental understanding of their scope and lifecycle. Refer to sections 4, 6, and 7 of the EJB 2.0 Specification.
Regards,
Tony "Vee Schade" Cook

EJB 3.1new instance of stateless session bean not created on new invocation

I am using Netbeans 6.8 bundle that comes with JAVA EE 6. I have created a web application then created restful web services and then created few stateless session beans (with local interfaces) that are invoked from restful web services. From the browser, when I call the url with get method, restful web services are being invoked and they in turn calls stateless session beans and does the appropriate business logic. While testing, I observed that for every new url call from the browser, the same bean is being invoked. I tested this by adding a instance variable vector and adding one item ('test") to the vector in bean's method. My understanding is that on every bean's method invocation the vector should have only one item. However, the vector is growing with many "test" items. I am literally confused, not sure this is the way it is supposed to work. I tried to invoke bean's method from restful web service by using both dependency injection and jndi look up, both instances the vector is growing with many "test" items.
I would really appreciate if some body gives me more insight.

I appreciate your answers. There is a strong reason for posting this question. Basically, I am using JPA and using stateless session beans to invoke database calls. In the bean I am using the following code for entity manager.
@PersistenceContext(unitName = "AsgProtocolServerPU")
private EntityManager em;
I have noticed very strange scenario while getting records. From the application, I have obtained few records of a table. Then, I manually deleted few records from the table. Very strangely, I have obtained the deleted records during my next call to bean. After 2 hours, I tested the same and did not get those records. This is not consistent.
I am totally confused. I am just wondering this is happening because I made beans local (not remote) and placed them in the web application (Java EE6 allows this). I am not sure whether this is JPA related issue or beans issue.

Newbie: How do i use a stateless session bean in a backing bean?

I have a stateless session bean with a function 'getVoterList()'; how do i instantiate the bean and use it in from my managed bean?
I dont want to use seam; coz the stateless serrion bean/EJB is written by another developer and we cant updat eit now to use seam..
any tutorials? walk thrus or sample code?
thanks
illi

I used a different method...
I used servicegen with only a.jar to create the ear.
I touch-ed my own application.xml to make it newer than the one already in the
newly created ear.
I used the ant <ear> task to add b.jar, c.jar, and application.xml to the ear.
Worked like a charm.
Mike
Bruce Stephens <[email protected]> wrote:
Hello,
See if Neal's answer here helps solve your problem using servicegen's
service element "IncludeEJBs" attribute:
http://newsgroups.bea.com/cgi-bin/dnewsweb?cmd=article&group=weblogic.developer.interest.webservices&item=2932&utag=
HTHs,
Bruce
kk wrote:
This is my situation.
I have an .ear file and in that i have several other .jar files whichare
inter-dependant, lets say
A.jar
B.jar
C.jar files
and i want to expose only A.jar as
webservice, how can i do that ?
Does WLS8.1 provided any way how to do that?
I Appreciate any suggestions and advices.
Thanks
kk

How to integrate hibernate with Stateless Session bean in weblogic10.0

Hi,
I need to invoke hibernate(3.x) DAO from EJB Stateless Session bean(EJB2.x). I am using mysql database. Can somebody please post the configuration.
Thanks in advance,
Rushi.

Hi Deepak,
Thanks for your reply.
Actually, our stand alone java application already using spring-hibernate feature. Now we are planning divide our application into modules and deploy each module as ejb beans. As it is already integrated with spring-hibernate we are not using entity beans as of now. My understanding is container uses some default transcation management .so, my question is what are all the configurations needs to be done to let weblogic 10.0 server uses org.springframework.orm.hibernate3.HibernateTransactionManager. I mean, is there are any .xml file in weblogic to configure all these? please reply deepak I am struck here..
Regards,
Rushi.

A tough one for EJB experts - Stateless session bean spec question

I am busy learning more about EJBs and came across something confusing regarding the legal operations in the various container callback methods for stateless session beans.
Specifically, the EJB spec states that in the ejbCreate() method, the SessionContext can be used to obtain a reference to the EJB Object. Now this makes perfect sense with stateful session beans, since the ejbCreate() method isn't called until a client is creating a bean and the container has linked that bean to the client's EJB Object. However, it is my understanding that when it comes to stateless session beans, the container creates the beans and adds them to the bean pool at its leisure. It is not until a business method is called by a client that a stateless bean is actually linked to an EJB object. So, how is it that a stateless bean could ever obtain a reference to an EJB Object from within ejbCreate(). Which EJB Object would it be linked to? This operation just doesn't appear to make sense in that context.
Can anyone clarify this for me?

Interesting question. I have such questions all the time! Here's a link to a similar discussion
http://saloon.javaranch.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic&f=70&t=000905
Also, I tried this using Weblogic 8.1. Tried to access the EJBObject in ejbCreate before any business method was invoked. I did this by specifying a value for initial-beans-in-free-pool and found that the hash code for the EJBObject was the same for all the bean instances that were created on startup.
I then invoked a business method and accessed the EJBObject in that method. Again the hash code for the object was the same as the one created on startup.
Seemed to be that there is a 1:n relation between the EJBObject and bean instances.
This may be container specific. The spec says the user should be able to invoke the getEJBObject() method in ejbCreate(), its upto the container to comply with it.

Transaction management in stateless session beans.

Hi all,
I am using EJB 1.1.
I have a statless session bean that has two methods- A and B.
which does not involve any database interaction
like inserting/updating/deleting the data in the database.
The process flow is such the client always calls A first followed by the call to B.
I have the Transaction attribute set as TX_REQUIRED at the whole bean level.
Now my question is as follows:
Since it is a stateless bean, ejbCreate() is called for every method's invocation.
So does it mean that a new transaction is started for every method invocation?
Also since a transaction ends by commit/rollback.
The transation associated with the method A/B will never get completed as there is no commit/rollback involved in method implementation.
So how is this transaction ended?
Any more details about the transaction management in stateless session beans is highly appreciated.
Any input at the earliest is highly appreciated.
Thanks in advance.

Since it is a stateless bean, ejbCreate() is called for every method's invocation.For stateless session bean , Create() is not delegated to the instance.
So does it mean that a new transaction is started for every method invocation?This depends opon the Tx attribute and sequence of calls. Since you have given Tx_required then if you call any method and there is no Tx context associated with client,then a new TX will be started by container othere wise it will execute in the same TX context as the calling client. Note that client can be jsp or other ejb method.
Also since a transaction ends by commit/rollback.
The transation associated with the method A/B will never get completed >as there is no commit/rollback involved in method implementation.
So how is this transaction ended?If you are using COntainer managed TX then Transaction handling like starting , ending etc is handled by the container. You need not worry about that.
Any more details about the transaction management in stateless session >beans is highly appreciated.
Any input at the earliest is highly appreciated.Some time back I had read the article on how the Transaction management done by container on IBM Site. I dont have URL , but you can search the site.
HTH
-Ashwani

Paradox - Should entity CMP EJB be faster than stateless session bean?

Please bear with me on this.
Just thinking of this scenario: hello world application. It can be implemented both as stateless session bean and entity bean.
There's no persistent. So for the entity bean, it will be container managed, and no code to do anything to the load/remove/create. - comparably the same as stateless bean.
Next, for the stateless session bean, each client call would require a dedicated instance of the EJB on the server (although for a very short amount of time). For the entity bean, it's shared, so only 1 instance is needed. It's also thread safe.
So, for a very high traffic, shouldn't the entity bean do better because of single instance?
What's other overhead?
Does the entity bean cost more connections than the stateless bean?

Feels like a comparison between apples and oranges.
A stateless session bean is like every other instance, so these can be pooled by the EJB container. The container is free to create an instance for each client if necessary. That's different.
A stateless session bean doesn't have to deal with a database that may or may not be located on another machine the way an entity bean does. There could be another network round trip involved. That's different.
Session and entity beans are intended for entirely different purposes. Just because you can write Hello World with both doesn't mean it's representative of what EJBs are used for. I don't think it's a good, meaninful comparison. JMO - MOD

Registering EJB/Stateless Session Bean Web Service in Registry

Hi verybody!
I would like to know how I can register a Web Service in a registry. The web service is implemented as a session bean.
The problem is not the actual code to register the service, but how and where can I hook this code into the application so that it is started when the application server is started.
I've read the Sun J2EE tutorial which registered the service in the moment when the context for the servlet for an ordinary web client was created. This is not what I want. I would like to register the service when starting the EJB container, without the need to give it a kick from some external interface.
Any help or ideas will be greatly welcome
Regards
PI

1. But I thought you were using a 'stateful session bean'?
2. For stateless session beans, there is no direct link between a remote reference and an instance of the bean. It is safe to hang on to the remote reference as long as you would like, of course it may go stale if the server dies. You will also find that the create() method does not actually contact the server, so doing it each usage costs very little. So, either way you should be fine.
3. As for memory leaks, make sure that you are closing all statements, result sets, etc. promptly. These are commonly the problem. Also, use hprof or some other profile tool to determine what types of data you are allocating and (with better tools) what types of data you may be holding on to references to.
Chuck

Call stateless session bean EJB 2.0 from Webdynpro Java UI

Hello,
Can someone please tell me asto how to call a stateless session bean EJB 2.0 from Webdynpro Java UI?
The NWDS version is 7.0.
Thanks and Regards,
Arya

Hi Aryadipta
Please check this pdfs
https://www.sdn.sap.com/irj/scn/index?rid=/library/uuid/b00917dc-ead4-2910-3ebb-b0a63e49ef10&overridelayout=true
Steps for calling stateless session bean in Webdynpro java
Go to NWDS -> open perspective ->j2ee
select EJB Module Project ->create a project with name
Open the Project -->RC on ejb-jar.xml -> Select new --> EJB
Give name to EJB Bean (First letter should be in capital letters)
select the type of bean as Stateless session bean and give the package name to store that EJB bean.
After that Expand ejb-jar.xml and then select the <projectEJB>
Double click on this on method tab double click you will get business method where we will create the methods for business logic
Double click on projectEJB and then RC on bean tab and write required business logic in bean window as follows(based on requirement we will design a business logic).
After writing the business logic go to project -> rebuild
Till now we have created one EJB jar file
then go to File-->Enterprise Application Project -->create a project (projectEAR)
After creating a project click on next-> here we will have ear projects and then we select specific project required for our application.(here select projectEJB)
After that Calculate EAR project will be available on j2ee explorer.
Right click on <Bean> here
select New->Web Service->give a name to webservice and select Default configuration type as simple SOAP
-->click next -> Finish.
That webservice and related are created in ejb-jar.xml .
Expand the ejb-jar.xml.and double click on < webservice>
RC ProjectEJB -> Build EJB Archive RC on CalculateEAR ->Build applicationarchive.
Expand the projectEAR->RC on CalculateEAR.ear->Deploy to J2EE Engine
Double click on calculateEAR.ear ->Webservice navigator tab ->we eill servers expand the node
select the specific WebService
Here we test the webservice by click on Test and test it.
After that go to Web dynpro perspective ->create one webdynpro Project and one component
RC on model> Select import Web Service model(last)>give model name and package
and select radio button as local file system or URL
Go to WSnavigator->copy the WSDL path and paste it in model WSDL path and click on finish.
from here onwards steps are same as that adaptive RFC model
Hope it helps
Thanks
Tulasi Palnati
Edited by: Tulasi Palnati on Aug 26, 2009 12:15 PM
Edited by: Tulasi Palnati on Aug 26, 2009 12:43 PM

WLS10 and Stateless Session Bean

I tried to create EJB3 application example.
1. Created Stateless Session Bean that implements Remote and Local interfaces:
Session Bean code:
package com.session;
import javax.ejb.Local;
import javax.ejb.Remote;
import javax.ejb.Stateless;
import javax.ejb.TransactionAttribute;
import javax.ejb.TransactionAttributeType;
@Stateless(mappedName="SessionBeanService")
@Remote(ISessionBeanRemote.class)
@Local(ISessionBeanLocal.class)
@TransactionAttribute(TransactionAttributeType.REQUIRED)
public class SessionBean implements ISessionBeanLocal,
ISessionBeanRemote
public String reply(){
return "MySessionBean - success !!!";
Remote Interface code :
package com.session;
public interface ISessionBeanRemote
public String reply();
Local Interface code:
package com.session;
public interface ISessionBeanLocal
public String reply();
application.xml:
<?xml version="1.0" encoding="UTF-8"?>
<application xmlns="http://java.sun.com/xml/ns/javaee"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
          http://java.sun.com/xml/ns/javaee/application_5.xsd"
     version="5">
     <display-name>EJB3 Sample Application</display-name>
     <module>
     <ejb>beans.jar</ejb>
     </module>
</application>
weblogic-application.xml:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE weblogic-application PUBLIC
     "-//BEA Systems, Inc.//DTD WebLogic Application 8.1.0//EN"
     "http://www.bea.com/ns/weblogic/90/weblogic-application.xsd">
<weblogic-application>
          <classloader-structure>
               <module-ref>
                    <module-uri>beans.jar</module-uri>
               </module-ref>
          </classloader-structure>
</weblogic-application>
2. I packaged classes into EAR file and deployed to WLS10.
I didn't include any weblogic specific XML descriptors besides weblogic-application.jar.
My client code lookes as follows:
public void test(){
Context context = getMyServerContext();
// THIS JNDI NAME I SEE ON MY SERVER JNDI TREE
String jndiName = "sessionbeansbeans_jarSessionBean_ISessionBeanRemote";
Object obj;
obj = context.lookup(jndiName);
System.out.println(" obj class : " + obj.getClass().getName());
ISessionBeanRemote remote = (ISessionBeanRemote) PortableRemoteObject.narrow(
obj, ISessionBeanRemote.class );
String res = remote.reply();
System.out.println("res : "+res);
I get an Exception:
Exception occurred!
java.lang.ClassCastException: Cannot narrow remote object to com.session.ISessionBeanRemote
     at weblogic.iiop.PortableRemoteObjectDelegateImpl.narrow(PortableRemoteObjectDelegateImpl.java:242)
     at javax.rmi.PortableRemoteObject.narrow(PortableRemoteObject.java:137)
     at ca.cgi.mvest.test.server.wms.GlFacadeTest.runTest(GlFacadeTest.java:91)
     at ca.cgi.mvest.test.server.wms.GlFacadeTest.<init>(GlFacadeTest.java:53)
     at ca.cgi.mvest.test.server.wms.GlFacadeTest.main(GlFacadeTest.java:151)
java.lang.ClassCastException: Cannot narrow remote object to com.session.ISessionBeanRemote
My server console have the following output:
Root cause of ServletException.java.lang.NoClassDefFoundError: com/session/SessionBean_7pp7ls_ISessionBeanRemot
eIntf
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:620)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:12
4)
at weblogic.utils.classloaders.GenericClassLoader.defineClass(GenericCla
ssLoader.java:338)
at weblogic.utils.classloaders.GenericClassLoader.findLocalClass(Generic
ClassLoader.java:291)
Truncated. see log file for complete stacktrace
Server logs a problem already on the line when I do lookup
on JNDI name even before narrow();
It looks like my EAR was missing something. But server never complained during deployment.
May be someone can direct me to a real sample of Weblogic10-ejb3.0 application, since examples that come with WLS 10 intallation combersome and do not follow
docmentation.
Thanks in advance for any suggestion.

Hello Freind
The main different b\w stateful and statless is that stateful maintain state of method conversation means it has record that which method call before this method
but in case of stateless conversation state does not saved second different we can say that create method in stateless having no parameter but statefull having parameter I think u can understand easily
With Best Regards
Rajesh Pandey
email :[email protected]
url :-- http://www.sixthquadrant.com
Mob :-- 9811903737
Delhi India

JCo 3.0 Server and Stateless Session Bean

Hello,
I use JCO (3.0) and I need to integrate SAP with JBoss.
The SAP Module is calling EJB-Services over JCo.
How would the architectur looks like?
I start with using an MBean to start and stob the native JCO-Server over JMX.
This still works.
But it doesn't work:
The Client(SAP) calls the JCoServer (works fine).
But the call off the EJB failed.
What solutions do you have to share?
Do you use a stateless session bean?
Best regards
Peter

The program ID should be with length 8 max

How Stateless Session Bean instances in pool

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