Vishal Vohra

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since Jun 03, 2008
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Recent posts by Vishal Vohra

Hello,

I have read in some books that only single instance of EJBHome is created irrespective of the number of clients accesing the Session or Entity beans.
Is it true and if this is so what will be its implications when multiple threads want to access the bean. I mean will it be thread safe?
Secondly, does it really need to be thread safe as there will be always unique instances of EJBObject and their corresponding Beans for these EJBHme instances.
Hello,

I have just started exploring EJB.
The first thing which I have read about EJB in every book, is that "EJB's are components and EJB's provide component architecture".
What does it mean? What are components?
Some people say that since EJB's run in a container, that is why, they are called components. But then, JAVA Beans are also called components and they do not run in any container.
So what does component architecture exactly mean?

The features that EJB provide can also be provided by coding in a plain JAVA class, then what is there in EJB's, that make them components.
Hello,

I am new to MQ and want to know how to setup the MQ environment.
I have WebSphere installed on my system with "MQ Messaging Provider" that comes with default with WebSphere.
I have found some PDF's from IBM explaining how to code using MQ Base JAVA and MQ JMS java classes, but I am finding it difficult to set up the MQ environment like the Queue Manager, Connection Factory, Queue itself and the destination.
I also came to know that this environment setting can be done with the help of JMSAdmin tool, but where I can find this tool.
On my system I have RAD installed with a plugin support for WebSphere, I mean the WebSphere has not been installed seperately, it is being used from the RAD and therefore I am not able to find JMSAdmin tool.

Please let me know how to set up Queue managers, connection factory, queue and the destination and once configured how can I administer them from WebSphere Administration console.
11 years ago
Campbell,

As I posted earlier, in every textbook and on internet, it is written that to reduce complexity is abstraction.
How does "using classes to represent the common features of similar things", helps in reducing complexity?
11 years ago
Fred,

as you said "abstract classes are one way of using abstraction, but not the only way", please tell me what are the other possible ways of using abtraction.
I mean I just want to know, to what all concepts can abstraction lead to in JAVA (for example it leads to a concept of abstract classes in JAVA).

Campbell,

do you mean, that "representing a bunch of similar things with the help of classes" is abstraction.
11 years ago
Thanks fred and Mark for your replies.

Fred,

Your post brings out the concept of Abstract Classes, does the concept of abstraction related to Abstract classes.

Mark,

According to the article on Wikipedia, Abstraction means -
"In computer science, abstraction is a mechanism and practice to reduce and factor out details so that one can focus on a few concepts at a time.

The following English definition of abstraction helps to understand how this term applies to Computer Science, IT and Objects - i.e. abstraction is:

A concept or idea not associated with any specific instance"

As the first part of the definition details about "reducing and factoring about details" - how is this achieved in JAVA.

Secondly, according to the second part of the definition does Abstraction means defining classes.

I found these definitions almost everywhere, so does abstraction really mean hiding implementation details and if it does, then does it also brings out the concept of interfaces and abstract classes which only provides method signatures and hide out the actual implementation from the end user.
11 years ago
I am a JAVA beginner, please explain Abstraction in a bit detail.
I looked in a lot of books, but could not get a practical explanation.
Everywhere it has been said that it implies reduction in complexity and to hide details and expose whatever is really necessary.
Please explain it in a bit detail. Also tell me how abstraction is achieved in JAVA.
11 years ago