what are the serious problems you had faced while using EJB's

alapatibk

 Profile Answers by alapatibk Questions by alapatibk

• Nov 11th, 2008

Just deploying the jar file will not help in Weblogic, you need to compile the ejb source using the ejb compiler "ejbc" supplied by weblogic.Otherwise we will see version miss match errors and it will not be deployed.I forgot the exact error number.

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Which are the jar files that need to be externally added to run a simple java program that accesses a session bean in EJB 2.0, using Jboss 4.X application server.

j2eenaru

 Profile Answers by j2eenaru Questions by j2eenaru

• Nov 18th, 2008

You just need to add either j2ee.jar file or jboss related j2ee jar file

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How to make the connection to JMS queue using EJB 3.0, Weblogic 10.3

yogesh chandra

• Dec 27th, 2014

"java Context context = ClientUtility.getInitialContextForClient(); System.out.println("test load.............................2"); QueueConnectionFactory...

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What are the contents of a web module?

Satish gupta

 Profile Answers by Satish gupta Questions by Satish gupta

• Oct 29th, 2011

A small unit of a web resource which can be deploy, can be used in our application is a web module.

for our banking or any other business application J2EE platform is a web module.

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Sandhya.Kishan

 Profile Answers by Sandhya.Kishan Questions by Sandhya.Kishan

• Jun 22nd, 2012

The Connection Pool Manager is used to establish a connection between two ear files.

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Answered by Jey on 2005-05-08 19:35:35: There are three isolation levels in Transaction. They are 1. Dirty reads 2.Non repeatable reads 3. Phantom reads.  Dirrty Reads If transaction A updates a record in database followed by the transaction B reading the record then the transaction A performs a rollback on its update operation, the result that transaction B had read is invalid as it has...

Ahmed

• Feb 14th, 2006

Isolation levels are Dirty_Read, Non Repeatable read and phantoms. These are the inconsistancies which are occured in transactions. To avoid these inconsistencies , we have 4 types of attributes.TRA...

J. P. Naidu

• Jul 28th, 2005

TRANSACTION_READ_UNCOMMITED TRANSACTION_READ_COMMITED=== Avoids dirty read  TRANSACTION_REPEATABLE_READ ===Avoids Non repeatable re TRANSACTION_SERIALIZABLE=== Avoids Phontom reads

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nemashailendra

 Profile Answers by nemashailendra Questions by nemashailendra

• Mar 25th, 2010

Use the callback methods ejbActivate() and ejbPassivate() to throw a user-defined message whenever the container calls these methods to activate or passivate a stateful session bean instance.

J. P. Naidu

• Jul 28th, 2005

In Stateful session bean session is not itself a separate entity. it is contained in the bean it self. So in order to check tht we need the check whether the Stateful session bean is present or not which is done by just invoking the home interface with the jndi

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khan

• Jul 29th, 2005

According to EJB 2.1 specificationThe EJB QL consists of 4 clauses: SELECT, FROM(mandatory) WHERE and ORDER BY(optional).

Srinivas Jadcharla

• Jul 18th, 2005

The EJB QL query string consists of three clauses: SELECT, FROM, and WHERE.WHERE is optional.

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Answered by Jey on 2005-05-08 12:59:41: Deployment Descriptor is a XML document with .xml extenion. It basically descripes the deployment settings of an application or module or the component. At runtime J2EE server reads the deployment descriptor and understands it and then acts upon the component or module based the information mentioned in descriptor.   For example EJB module has a deployment...

kirankpv

 Profile Answers by kirankpv Questions by kirankpv

• Feb 9th, 2008

Deployment Descriptor is a XML document with .xml extenion. It basically describes the deployment settings of an application . At runtime webcontainer reads the deployment descriptor and understa...

Jey

• May 8th, 2005

Deployment Descriptor is a XML document with .xml extenion. It basically descripes the deployment settings of an application or module or the component. At runtime J2EE server reads the deployment des...

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Answer posted by Mohan on 2005-05-21 17:21:54: yes the rollback will occur

hari ambati

• Oct 25th, 2006

We need to call explicitly.setRollback() Method to roll back the transaction in this. Container calls this automatically in case of system exception or system crashes.

Denis Wang

• Jun 30th, 2005

For declarative transactions, container will rollback on systemException. Container has no way to know whether a speicific application exception is serious enough to roll back the participated transaction. Use setRollbackOnly() to doom the transaction.

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rajeev

• May 31st, 2007

It is possible. But J2ee spec restricts the use of certain api's for eg Reflection, io,etc.;)

Raja Seklhar reddy T

• Sep 11th, 2005

You use reflection when you actually instantiate the objects or invoke the method.In the EJB Scenario Beans invoke other Beans as clients. The client only looks up the objects (not instantiating) and ...

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nemashailendra

 Profile Answers by nemashailendra Questions by nemashailendra

• Mar 25th, 2010

Message driven beans cannot be instantiated by a client application. The container creates the mdb instantiates an mdb each time a message is available on a jms queue. Hence by default each message is...

Anand

• Apr 26th, 2005

The MDB is stateless and inherently each message is unique with respect to the MDB. Each message needs to be processed independently. Hence the need for separate transactions

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Answer posted by Mohan on 2005-05-21 19:24:23: All Beans support Instance Pooling

Vj

• Jul 22nd, 2005

EJB does indeed support the effect of pooling stateful session beans.Only a few instances can be in memory when there are actually many clients. But this pooling effect does not come for free---the pa...

raj

• Jul 4th, 2005

Statefull session bean does not maintain instance pooling, stateless session beans and entity beans can maintain instance pooling

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This was the answer Provided by some one... According to Mohan this one is not correct. Please see Mohan's reply below and more in the comments section. ejbRemove() is called for session beans every time the container destroyes the bean. So you can use this method to do the stuff you typically would do in unsetEntityContext(). For entity beans ejbRemove() is only called if the user explicitly...

Madhavikari

 Profile Answers by Madhavikari Questions by Madhavikari

• Apr 20th, 2006

For session beans, there is no need to call the for removing the instace of a bean. If the session is expired automatically the ejb container will remove the instance of the bean.But, for entity beans...

Mohan

• May 21st, 2005

To elaborate typically ejbRemove may be called on a been n number of times during it's life time .. but unsetEntityContext will only be called once on a bean.

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Answered by Jey on 2005-05-08 11:06:46: When the EJB container needs to synchronize the instance variables of an entity bean with the corresponding values stored in a database, it invokes the ejbLoad and  ejbStore methods. The ejbLoad method refreshes the instance variables from the database, and the ejbStore method writes the variables to the database. The client cannot call ejbLoad...

Vj

• Jul 22nd, 2005

Note: ejbLoad and ejbStore methods are to be coded only if you are creating a BMP. For CMP these methods are handled by the container.

Sanjay Guha

• May 25th, 2005

ejbLoad method: This method is called when it is necessary to synchronize the bean with data from the database. This will most likely trigger a SELECT to occur. The ejbLoad is triggered when the ...

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Inside an EJB you may retrieve the "Caller" name, that is the login id by invoking: sessionContext.getCallerIdentity().getName() where sessionContext is the instance of "SessionContext" (setSessionContext) passed to the Session Bean, or the instance of "EntityContext" (setEntityContext) passed to the Entity Bean.

Sony V George

• Apr 4th, 2007

You can get the User Name? by using the following codesessionContext.getCallerIdentity().getName() There is having two types of context 1.SessionContext2.EntityContext

uma

• Feb 12th, 2006

u can get the information abt the client(who invoked the bean) by the EJBContext methods.There r 2 types1)SessionContext and 2)EntityContext.These r used get the information abt the container,the client and get reference of the bean itself.

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gambhirgaurav

 Profile Answers by gambhirgaurav Questions by gambhirgaurav

• Jan 20th, 2006

Yes we can have instance variables in Stateless Session Bean ,but these are not used to maintain the client specific state.

gokulakrishnan

• Sep 30th, 2005

No,In Stateless it does not maintain the contexual information about the client.In statefull we are having the ejbActivate(),ejbPassivate() bcoz it maintains the user specific data. but if we are giving the activation and passivation in stateless the container won't take these methods.

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Sony V George

• Apr 4th, 2007

We can improve efficency through Pooling. If you are asking how we can balance the load, we can do it through clustering so that we can balance the load. this one will reduce the server balancing. You can take either one .

CDT

• Sep 17th, 2005

In plain English, I think this question is asking how EJB is more efficient as user load increases. The correct answer is pooling. Pooling is implemented differently across application server implem...

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Vijay

• Nov 1st, 2005

Hi All,The stateless bean is used whereever the logic does the same for all client irrespective of remembering the client state.For Example, Consider a simple EJB Client which just converts dollar to ...

Sree Ranganath

• Oct 26th, 2005

I  dont  think that St less bean is  used in this scenario  (ie.,   Credit card processing ) coz there it is a must that we have to remember the client.

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Tamil Selvan

• May 28th, 2007

To access a servlet/jsp from EJB create a URL and call its openStream() method.URL google = new URL("http://www.google.com/"); BufferedReader in = new BufferedReader(new InputStreamReader(go...

ArulJothi

• Sep 18th, 2005

JSP or Servlet can communicate with EJB by giving the jndi name of that EnterpriseJavaBean in the lookup method of InitialContext.It will return a reference for the home interface of EJB.

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