Proxy object and entity Bean interaction

Hello,
I'd like to have some precisions on the interactions between the proxy object (client) and the entity bean(server):
- does J2EE provides ways for a bean to manage clients, to define roles and permissions, lock, etc ... ? What informations an entity bean can know about the clients ?.
- how does the context mechanism work on the entity bean side ?
- how does an entity bean identify different clients ? how does it recognize one from another ? I mean if client c1 and client c2 use same entity bean B, how B can manage different roles for c1 and c2, and how can B returns specific values to a particular client.
Thx.

If you can read some tutorial, you will get all the information.
I'll suggest a book EJB by richard manson publicvations oreilly.
The activities you are talking about is responsibility of container and user developed bean are totally absytracted from this system level activities.
Primary service include security which take care of activities like Authentication, access control and secure communication.
for role based access control u have container providing the identity by Principal object. DDescriptors declare which logical roles are allowed to access even perticular method of the bean.

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Hi All,
Can any one help me how is the flow of session and entity beans i.e
What method is called first and what method is called next.
There are so many methods like create(),ejbcreate(),
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Hi vasudulla,
If you can, go to the bookstore and look for the book:
Entreprise JavaBeans 3rd Edition by Richard Monson-Haefel.
In the Appendix B, you can see the State and Sequence Diagrams, all the things you want to know about the Flow.
--Paul.

How many ejbCreate() can be in Session and Entity Bean???

Hi,
How many ejbCreate() method can be in a Session and Entity
Bean???
How many can be in Stateless and Stateful SessionBean???
How many can be in CMP and BMP SessionBean???
Thanks,
JavaCrazyLover

How many ejbCreate() method can be in a Session
ion and Entity
Bean???For Stateful Session Beans and Entity Beans, as many as you'd like.
Stateless Session beans can only have one, since their ejbCreate methods can not take any parameters.
>
>
How many can be in CMP and BMP SessionBean???If you mean CMT/BMT(Container-Managed transactions / Bean-Managed Transactions), then
the answer is the same. The create method requirements are independent of the transactional nature of the bean.
If you really mean CMP/BMP(Container-Managed Persistence / Bean-Managed Persistence) , it doesn't apply to session beans, only entity beans. However, even for entity beans, CMP vs. BMP has no bearing on the rules regarding # of create methods.
--ken
>
>
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JavaCrazyLover

JSF and entity beans

I'm trying to create an application using JSF for the presentation layer and entity beans and stateless session beans in the model layer using CMP, for deployment with JBoss. I'm basically stuck though on the communication between the backing bean and the session bean (where do I define the JNDI names, the database connection etc). Can anybody suggest a good tutorial/example showing JSF with EJBs?

Well I was interested in the same topic, I once thought `Sun Java Studio Creator EA2` will have an easier approach ... well it dun seems easy to me neither.
Anyone of you tried acheiving the purpose by using that approach b4?
I'm currently working on a `JSF-based portlet` project with `entity beans + managed beans` ... well its very much source shared ... but I'm still green :P
Anywhere, I'm starting a new thread called `JSF Portlet developement` in my blog (`http://avatar21.superihost.com`), feel free to comment(any ideas will be mostly appreciate).
Regards,
Avatar
there is no specific support in JSF for EJBs.
the definition of connection pools and other JNDI
resources are subject to the servlet spec which JSF
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you can find usefull examples in the sun J2EE
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Object Oriented Databases and entity beans?

Does one of the authors care to comment on the benefits of using OODBMS models versus RDBMS models for entity beans? Any differences between BMP and CMP in this scenario?
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Bump?

8.1.7 and Entity Beans. Where is Patch 8.1.7.1???

I would like to be able to deploy CMP Entity Beans to 8.1.7 on Solaris using JDeveloper 3.2.2
The release notes indicate that this is a bug and is awaiting a patch. My two questions are:
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2. Could someone please describe for me the best way to write a CMP Entity Bean in JDeveloper 3.2.2 (w/descriptors & JAR'ed etc...) and then use the Oracle Command Line tools to load this bean? ie. what are the pitfalls?
Thanks in advance.

Thx alot..
When will JDev 3.2 be available for evaluation download ?
(The firm im working for is about to buy a complete system from the east, and i need to know how things perform before recommending purchase of system/archtecture and oracle tools).
Incedently, i experienced a problem with session beans on 8.1.6, if i killed my client app somewhere along a lookup and remote.create the sessionbean would completely die, only thing to do was to redeploy it(not even reboot cured it) (i could create it, but reading serilized objects gave a marshall exception every single time..)
I want to know if this is a known issue? and if it is, has it been 'fixed' in 8.1.7?
By the way, everything is running on localhost on a win2k pro box.
Thx alot for your time.

Basic difference between stateful and entity beans???

Could anyone please explain the basic diff between stateful bean and an entity bean.as per my understanding,stateful beans are extensions to clients.they perform a job of a client and they r not persistent.also their state goes off when the server crashes or the machine is reeboted.while in contrast,an entity bean can retain its session coz' they represent a persistent field in the DB.What i have seen in few books(O'reilly,etc)where a session bean can insert some values into the DB,which means it also represents a persistent object in the DB,which contradicts the statement that "stateful session beans dont represent any persistent object in the DB".Could anyone please elaborate on this.Thanks in advance.
Jameel

Thank u very much crackers for ur valuable
suggestions.I'll throw a different one in here for free: clarity of writing is a highly-valued and useful skill in a software professional. This is especially true these days when concepts need to be clearly explained to a variety of technical peoples from all over the world. And then there's the other side of the coin: Management.
You have to get your thoughts across in a very precise manner and, unfortunately for those who have to learn it as a second lanugage, English seems to be the overall preferred medium. Which makes it even more important to use "correct" English in written communications. If you don't, your credibility diminishes and you appear to be (horrors!) unprofessional It's not that much harder to type "you" than it is to use a single letter. Besides, most people that "pay by the byte" appreciate the clarity, as well (as I've seen on Usenet, by way of covering my ass).
Now, back to our regularly scheduled post...
Is this wat u were trying to say if i
understood u correctly.Yes, the EntityBean is directly related to the data being persisted: in this case, a database table. So, using your example from below, the DB table would have two fields: a VARCHAR 'Name' and an INT 'Age.' The EntityBean would have corresponding fields/properties/variables, String name and int age.
"WHICH BEAN (Entity
or Sateful Session) SHOULD I GO 4???"No easy answer. The best one is: it depends. On what? It depends upon what you're trying to do with the data, how it's presented/manipulated, load requirements, environmental requirements, caching strategies, and about another dozen or so other high-level requirements.
My personal preference is if I need caching and the number of EntityBeans actually in existence is pretty "low" (another nebulous and arbitrary value, depending), I'll use a StatelessSessionBean as a Facade (search for "patterns" here in the forum), with the persistence in CMP EntityBeans. Which is influenced by the fact that I like playing with CMP. ;D

Type of Serialized Object for Entity Bean

Hi,
I develop a container managed persistence entity bean. I want to persist an object that is serializable into a database column. My database column type is a Blob. I wonder what is the type of a field in my entity bean? Please help. Thanks in advance.
Cheers,
Paul Ngo

Providing you are not worried about referential integrity, CMP will do this automatically.

DAO and entity bean

I have an entity bean which has a lot of gets and set methods. i am calling all the methods in a DAO. The DAO Recognizes all the old methods but not the last one, i dont understand why a single get Set is not being recognized.

Your question is not very clear. Could you tell the problem in details?

Web services and entity beans

Hi,
I want to implement a web service which stores some information.
I decided to bulid it using ejb.
Can i expose a web service as an entity bean?
If so,can anybody introduce me some example?
If not,what is the solution?

Yes, u can do that by creating EJB controls first and then add that EJB control to WebService.
Which Editor is using . if u r using Weblogic Workshop 8.1
Creat project and then just right click and create EJB Control for that and then add this to web Service
If u wanna any other information reply ..

RemoteExceptions and Entity bean failover

The documentation gives an example of how to achieve failover with
          entity beans. (See below). How can one tell that the RemoteException
          is due to the server being down rather than some other reason.
          For example in EJB 1.0 aren't many exceptions generated in the bean
          wrapped in a RemoteException? For example if there is an SQLException
          the bean might throw a RemoteException that wraps the SQLException. In
          such a case it doesn't make sense to try it again.
          So what is the correct way to find out whether the exception is due to a
          server failure rather than some other reason?
          dan
          AccountHome home =
          (AccountHome)ctx.lookup("example.AccountHome");
          Account account;
          int attempts;
          while (attempts < LIMIT) {
          try {
          tx.begin();
          account = home.findByPrimaryKey(ACCOUNT);
          account.deposit(500);
          account.withdraw(10);
          tx.commit();
          break;
          catch (RemoteException re ) {
          // Retry
          try {
          tx.rollback();
          attempts++;
          catch (Exception e) {
          // Something unrecoverable has happened
          throw e;


Yes, this is the "nasty" case as I've heard several people put it. It's among the
          problems that make distributed programming difficult. Since the database is managing
          the transaction log, the other app servers in the cluster do not know if the tx was
          committed or not either.
          -- Rob
          dan benanav wrote:
          > If a remote exception is thrown from an entity bean then is it the case that we know
          > the transaction has rolled back? What if the server went down after the transaction
          > was committed?
          >
          > dan
          >
          > Rob Woollen wrote:
          >
          > > dan benanav wrote:
          > >
          > > > Isn't there a more definitive way to determine whether the problem is due to a
          > > > connection error or the server being down?
          > > >
          > >
          > > My first answer to your question is why do you need this? Both a db
          > > connection error and the server going down should be relatively rare events in a
          > > production system. RemoteException is meant to indicate that a system-level
          > > error has occured and the transaction has rolled back. Doing another find in
          > > this case is not going to limit your application's performance / scalability.
          > >
          > > -- Rob
          > >
          > > >
          > > > Rob Woollen wrote:
          > > >
          > > > > dan benanav wrote:
          > > > >
          > > > > > The documentation gives an example of how to achieve failover with
          > > > > > entity beans. (See below). How can one tell that the RemoteException
          > > > > > is due to the server being down rather than some other reason.
          > > > >
          > > > > Any application error should be thrown as an application exception that
          > > > > you could obviously distinguish from RemoteException.
          > > > >
          > > > > As you correctly point out, db errors like SQLException are often
          > > > > wrapped in RemoteException when they reach the client.
          > > > >
          > > > > I would code the application to give up if it gets an application
          > > > > exception. For instance, if you try to withdraw more money than you have,
          > > > > there is no sense in retrying.
          > > > >
          > > > > I would retry (up to a small limit) on RemoteExceptions if it makes
          > > > > sense in your application. Even SQLExceptions may be transient. For
          > > > > instance, Oracle may not have been able to serialize your transaction on
          > > > > the first attempt, but your second try might go through.
          > > > >
          > > > > -- Rob
          > > > >
          > > > > >
          > > > > >
          > > > > > For example in EJB 1.0 aren't many exceptions generated in the bean
          > > > > > wrapped in a RemoteException? For example if there is an SQLException
          > > > > > the bean might throw a RemoteException that wraps the SQLException. In
          > > > > > such a case it doesn't make sense to try it again.
          > > > > >
          > > > > > So what is the correct way to find out whether the exception is due to a
          > > > > > server failure rather than some other reason?
          > > > > >
          > > > > > dan
          > > > > >
          > > > > > AccountHome home =
          > > > > > (AccountHome)ctx.lookup("example.AccountHome");
          > > > > > Account account;
          > > > > > int attempts;
          > > > > >
          > > > > > while (attempts < LIMIT) {
          > > > > > try {
          > > > > > tx.begin();
          > > > > > account = home.findByPrimaryKey(ACCOUNT);
          > > > > > account.deposit(500);
          > > > > > account.withdraw(10);
          > > > > > tx.commit();
          > > > > > break;
          > > > > > }
          > > > > > catch (RemoteException re ) {
          > > > > > // Retry
          > > > > > try {
          > > > > > tx.rollback();
          > > > > > attempts++;
          > > > > > }
          > > > > > catch (Exception e) {
          > > > > > // Something unrecoverable has happened
          > > > > > throw e;
          > > > > > }
          > > > > > }

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There is a very good example in the otn in the forms-demo-section.
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