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Why an onMessage call in Message-driven bean is always a seperate transaction
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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How do you check whether the session is active in Stateful session bean
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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What is ACID
Answered by Jey on 2005-05-08 17:27:45: ACID is releated to transactions. It is an acronyam of Atomic, Consistent, Isolation and Durable. Transaction must following the above four properties to be a better one Atomic: It means a transaction must execute all or nothing at all. Consistent: Consistency is a transactional characteristic that must be enforced by both the transactional system...
opbehera
- Feb 8th, 2010
A - AtomocityC - ConsistencyI - IsolationD - Durability.When Transactoon(Tx) middleware service is enabled on the Businesslogic the data on the application available outside or in DB s/w&nbs...
Ritesh patni
- Jul 25th, 2005
Atomic-- should execute all or nothing...rollback come into picture Consistent--Consistency is a transactional characteristic that must be enforced by both the transactional system and the applic...
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What is EJB
opbehera
- Feb 8th, 2010
EJB is a distributed technology i.e capable of developing java based distributed applications, enterprise application & heavy weight business component giving the advantages of readyma...
sai.pappu
- Sep 26th, 2008
EJB is an server side component & its a WODA ( Write Once Deploy Any Where).EJB's run will under the control of EJB container.EJB is popular due to System level services provided by it.Developer can more concentrate on Business Logic due to services provided byu EJB.thanks.
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How can we update a row in the db using entity bean?
uppulafaq
- Jan 21st, 2010
Yes, we can update a row using entity bean.ejbStore() will do that.in BMP you have to write code to update the row.
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Comparison between ejb2.0 and ejb3.0
am577
- Dec 27th, 2009
The deployment descriptors are no longer required; everything can be accomplished using metadata annotations. The CMP (Container Managed Persistence) has been simplified; it is now more l...
thomaskm
- Apr 27th, 2007
The major differences i have seen between EJB 2.x and EJB 3.0 versions are as follows :- 1). Removal of home interface enabled simple lookup process in ejb 3.0 2). EJB deployment descriptors are not r...
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BLOB & CLOB
What is the expansion for BLOB & CLOB?
myogeshchavan97
- Jul 31st, 2009
Blob Stands for Binary Large Object.Clob Stands for Character Large Object.
itsvenuhere
- Jul 28th, 2009
BLOB: Binmary Large ObjectCLOB: Character Large ObjectBoth of these are used to store large amounts of data.
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When you will chose CMP and BMP
geeksterrahul
- Jul 23rd, 2009
CMP gets complex when the query involves two or more tables. In such case you might want to go for a BMP.BMP is a good choice when the task involves two or more tables.CMP does not have support for certain JDBC CICS. In such case BMP is a good choice.
gskumar
- Sep 12th, 2005
When ever you want to use SAP or any ERP concept for ur back end then it is better to go for BMP's .If u are very particular about the performance of application then better use BMP rather than using CMP.
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What is session facade
bhushanamca
- Jul 7th, 2009
Session Facade is a design pattern. It is used to reduce the network round trips between client and EJB comp. SLSB comp will act as session facade and it is receiving request from client and communic...
coolguy_krkr
- May 11th, 2008
Session facade is one design pattern that is often used while developing enterprise applications.It is implemented as a higher level component (i.e.: Session EJB), and it contains all the iteractions ...
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What is the difference between ejbstore and ejbload?
AkshataShriyan
- Jul 3rd, 2009
They are call back methods.They are used to notify ejb beans of the state.Called at the boundaries of the transaction.Whenever tx.begin(), ejbload() is called to notify beans of data being refreshedWhenever tx.commit, ejbstore() is called to notify beans that data is being persisted
VenkitaKrishnan
- Apr 20th, 2009
These 2 callback methods are avaliable in the EntityBean Interface and will be used by the container to load the data from the Database into the Bean (ejbLoad) and from the bean to the Database (ejbSt...
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How do you throw EJB/SQL exceptions to front-end/presentation layer ?
raju.k
- May 4th, 2009
In the JSP page we?specify an error page for that exception and forward the control to the specified error page when?an exception comes and we can display the exception in a good manner.
santanu_nandi
- Mar 9th, 2008
Inside the EJB code you put a try catch block. Inside the catch block you throw new EJBException. In the method signature also you declare that the method will thow the exception and not handle it.At ...
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What are the call back methods in Session bean
Answered by Jey on 2005-05-08 19:41:22: Session bean callback methods differ whether it is Stateless or stateful Session bean. Here they are. Stateless Session Bean 1. setSessionContext() 2. ejbCreate() 3. ejbRemove() Stateful Session Bean 1. setSessionContext() 2.ejbCreate() 3.ejbPassivate() 4.ejbActivate() 5.ejbRemove()
ganeshjava
- Nov 26th, 2008
Please note down that ejbCreate() is not a method of Session Bean, for reference see the link?http://java.sun.com/j2ee/sdk_1.3/techdocs/api/javax/ejb/SessionBean . html
Satish
- May 30th, 2007
Session callback methods setSessionContext();unsetSessionContext();ejbLoad();ejbActivate();ejbPassivate();ejbRemove();Entity bean call back methodspublic void setEntityContext(javax.ejb.EntityContext ...
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Jarfiles to be build in EJB 2.0
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.
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Have you faced Any problems while deploying ejb's in weblogic
what are the serious problems you had faced while using EJB's
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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How many clients can share a same instance of a stateful session bean?
muktasharad
- Sep 7th, 2008
Number of clients can share the same instance of above mentioned bean because in stateful session bean multiple clients are assigned with one instance only, so they would all share taht instance.thank you!
NIRAJ KUMAR
- Oct 20th, 2006
Hello Friends, Only one client can share a same instance of a stateful session bean.As the name suggested that stateful session beans maintained the session information of the client so only one client can share the same instance of a stateful session bean.
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Is it necessary to create instance of the bean for each and every request?
vinaykurudi
- Aug 13th, 2008
No, why because beans are maintaining?one bean pool. If any request comes to that bean it will first see in that pool if any instance is free, then that instance will be thrown to the request. If no ...
rogesh
- Jan 19th, 2006
I think 238 instances will created for one bean
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What is the difference b/w EJB2.1 and EJB3.0?
saankhya2003
- Jul 29th, 2008
The main difference lies in the persistence, In case of EJB 3.0 there?is JPA, Java persistence API which makes the mapping of EntityBeans with the database easy, with the help of a service called as ...
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What is the default transaction attribute in transactions
harish.verma
- Mar 6th, 2007
The default choice for a transaction attribute is Required. Using this attribute ensures that the methods of an enterprise bean are invoked within a JTA transaction. In addition, enterprise beans with...
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What kind of bean(entity/session) will you use if there are no database transactions and all you use is a read-only database.
coolguy_krkr
- May 11th, 2008
If you have no database transactions and you need just data fetch..I would not go for both of them..We can as well use simple dao with jdbc call to fetch data. If you have to pick one from the beans then definetely it would be stateless for this scenario.
s_s78
- May 3rd, 2006
If u are only reading the database then u dont need to use Entity been at all.Entity been slows down data fetch operation.U just need to use stateless session bean.
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PortableRemoteObject.narrow()
What is the purpose of the call to PortableRemoteObject.narrow()?
EJB Interview Questions
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