Raj Rad

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since May 20, 2002
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Recent posts by Raj Rad

I have been working and reading EJBs for a long, at least for 2 years. The way EJB Spec is changing is really boring. But I haven't written any 2.0 specific EJBs yet. Now they are with 2.1.
I would recommend you to write some sample EJBs on stateless/stateful Session and CMP/BMP entity beans. Should understand the lifecycle and pooling process. For example, you should know that ejbActivate/ejbPassivate methods will never be called on stateless session beans and 'Why?'.
Hi all JavaRanchers,
I cleared the part 1 last week on 2 Jan 2003. The exam preparation was really a great experience.
60% of the questions were from EJB. There was no single question on EJB API. It was completely on how you have understood EJBs, using appropriate types of EJBs, avoiding complexities etc. So concentrate on Designing EJB applications. Some questions were really confusing. In that cases, I had to approach the right answer by eliminating the wrong answers.
Compared to Programmer/WebComponentDeveloper exams, time was not sufficient for this exam. Since most of the questions were scenario-based, I couldn't do a complete review after answering the questions. I could review only the questions I had marked. So don't spend much time on questions which have stright-forward answers.
The break up is below.
Concepts 100%
Common Architectures 66%
Legacy Connectivity 100%
EJB 100%
EJB Container Model 100%
Protocols 100%
Applicability of J2EE 66%
Design Patterns 80%
Messaging 100%
Internationalization 100%
Security 100%
I would thank everyone for the nice discussion, notes and links for resources. I started off with notes for some topics, but later I gave up. I used print outs of EJB 1.1/2.0 spec, J2EE Blue prints, IBM security red book, Mark Cade guide, notes, articles, Java Server Programming-J2EE edition, Design Patterns(GoF), UML reference and a hi-lighter.
No EJB2.0 questions. This is really a boring spec that repeats so many things in so many places. Now they are coming up with 2.1.
You don't require much UML knowledge. But I would strongly recommend to read Design Patterns.
I understand your explaination and thanks for the same. But in both cases, the number of senders can be more than one, right? For example an Order processing system and a Stock trading system both can post Order confirmation and a trade confirmation to a single 'Response' queue. A single response processing system can fetch the messages and notify the clients appropriately.
My concern is the exam point of view. Should I say both domains always have 'single' sender?
As per the J2EE Blueprints,
1)The recommended way to manage transactions is through container-managed demarcation.
2)Transaction demarcation should be selected with great care by someone who understands the application well. Bean-managed transaction demarcation is only for advanced users who want fine-grain control over the transactional behavior of the application.
So which is the better way? EJB spec doesn't say the applicability clearly. J2EE tutorial also repeats the term 'fine-grain' control for the applicability of BMT.
Most people say that
Queue - One sender and one receiver
Pub/Sub - One sender and multiple receiver.
I don't think this is a rule. Because of the fact that any number of clients can send messages to a Queue or a topic. So the number of senders can be anything.
Whereas a Queue is intended for a single receipient and Topic is intended for multiple clients. JMS doesn't define the behavior for multiple clients listening to the queue, but it's intended for a single client.
My question boils down to the number of senders in both cases.
Is the number of senders is one or multiple in both cases?
I have been a member of javaranch for a while though I couldn't participate in the forums. I used to just sneak in sometimes.
I have changed my display name as 'Raj' now. I hope this is according to the policy.
Do I need to learn all these? Did anyone face any questions in the exam on these topics?
Thanks in advance
This is not an answer to your question. Are you Kali of TPGIT by any chance?
Do I have to study the J2EE patterns catalog?
I strongly believe this is "reverse proxy load balancing". Let me define these two terms.
Reverse Proxy load balancing: A single proxy server is located in front of a cluster of servers. The IP address of the proxy server is what mapped to the domain name the site represents. Whenever a DNS request comes for www.foo.com, the IP address of the proxy is what returned to the browsers. So what I mean is the proxy server REPRESENTS the whole cluster. Based on request type, the proxy might delegate the request to any one of the available cluster server. It might even be capable of avoiding a dead node.
Off board server: This is not at all related to load balancing. It's a wrapper/adapter kind of thing that can communicate to a legacy system and provide a standard interface to clients. For example, you can write a server in java that can talk to a mainframe system using Sockets and provide RMI/CORBA interfaces to it's clients.
Your example doesn't belong to "off-board" server definitely, but a simplified way of load distribution. Since all the requests are received by a single server, I would say it is a kind of reverse proxy balancing.