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This Weeks Giveaway

 
Carl Trusiak
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This Week we are giving away four copies of the book "Professional EJB".
Two of the Authors, Craig A. Berry and Matjaz Juric, are online to answer your questions!
For details, check out JavaRanch Book Promotions
Let's give Craig and Matjaz a warm JavaRanch Welcome

Thanks to Wrox for the books
 
Craig Berry
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Hi everyone,
I just wanted to add a quick post to let you know what my role on the Professional EJB book was. Basically I had a dual role. My primary responsibility was that I was the Technical Architect for the book. Now I realise that terms means very little so I'll try and give you a rough idea what it means.
I'm a Wrox employee and my job is to be the nexus for the book. In practical terms, I decide what book to publish, what the content will be, who will write it, as well as reviewing and editing the material. So basically I'm the one who pulls the whole book together. Additionally in this instance, I also wrote some material for the book.
So if you have any questions about the book as whole then let me know.
Ciao for now
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Craig Berry
Author of Professional EJB
 
Syed Hussain
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Welcome to JavaRanch.I learnt EJB sometime back, but after understanding I came to realize that there is no significant distinction made b/w an Application Server and Container defined in the EJB Specs.Is this correct.If it is, then this makes EJB platform-dependent , and thus ruining the "Java Way Of Life".
Syed.
[This message has been edited by Syed Hussain (edited September 11, 2001).]
 
Matjaz Juric
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Hi everyone,
It's nice to participate in Java Ranch.
I've been involved with distributed architectures, like CORBA, RMI, EJBs, etc. quite for a while and have specialized on performance. However I will try to answer other EJB related questions too.
Cheers,
Matjaz

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Matjaz Juric
Author of Professional EJB
 
Tom Ben
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Welcome Craig and Matjaz to javaranch.
I am new to EJB's. My company is beginning to use EJB's very heavily in our messaging services. I am curious as to what are some of the strong points of using EJB's
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Sun Certified Programmer on the Java 2 Platform
 
Anonymous
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Hi,
I'm new to J2EE & EJB, could some tell where I can get a brief
description of it.
Thanks
Yoel
------------------
Sun Certified Programmer for JAVA 2 Platform
 
ruilin yang
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Hi Authors,
It is nice to have a chance to ask you questions.
Do you have advice on how to map tables to Entity Bean ? Suppose I have 50 tables linked together. What is the guideline to map them to ejb's? Each table has to be mapped to a separate ejb ? Or can I map a few tables to one bean ? I feel that map every table to a separate bean sometimes can be mess if I have a lots normalized tables.
Thanks,
Ruilin

[This message has been edited by ruilin yang (edited September 11, 2001).]
 
James Nuzzi
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Welcome Craig A. Berry and Matjaz Juric!
Glad to have you.
------------------

James Nuzzi
SCJP, SCJD, SCWCD
 
Max Tomlinson
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Good topic.
Like many of you, I am getting involved in EJBs, but wonder what the authors have to say about the maturity of the technology.
At my current installation the decision was recently made to hold off on EJBs for the next year and stick with Servlets/JSPs as EJB containers do not seem ready for prime time.
As I see it the current drawbacks to EJBs are:
a) EJBs not truly interoperable amongst containers.
b) performance.
c) complexity.
For me, the first is the prime issue. We have found that EJBs developed with IBM's Websphere cannot be accessed by a non-IBM JVM. Although this is supposed to fixed by the end of the year, it's a proprietary trap. IBM isn't the only one either as it seems that all vendors encourage use of proprietary packages and tools. It seems that Session beans might provide a real future but Entity beans might fall by the wayside, as they are real victims of complexity and container specific services.
Max Tomlinson
SCJP, SCJD
 
Ricardo Polero
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Hi, I wanto to partricipate, in the next weeks I'll go to SCJE and EJB
Ricardo
 
Craig Berry
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Sorry guys, the events in NY kinda distracted me from the forum yesterday but I'll try to answer some of your questions now.
Tom, the obvious advantages of EJB come from them being in a managed environment (the container). This means it is relatively easy to incorporate container-managed services such as security, persistence, transactions etc. into your business code. They also provide benefits in the way of performance and scalability through the application server.

------------------
Craig Berry
Author of Professional EJB
 
Craig Berry
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Max, I think the 2.0 spec is a big step forward in terms of maturity but there is probably still a bit of way to go yet. The 2.0 spec also made some improvements regarding the interoperability of beans, for example the introduction of EJB QL. Entity beans have also changed significantly with the 2.0 spec, mainly for the better. Regarding the interoperability issue again, one aspect that never made it into the 2.0 spec was the identification of a persistence manager. This theoretically could mean you could use a different persistence manager product (to take care of CMP) than the main EJB container.
Performance is an issue if EJBs are not really being used appropriately. Because of the managed environment there is a fair amount of overhead involved in using EJBs, so you need to be sure that your requirements are such that using EJBs are justified. Having said that, there are of course methods that can be used to improve performance. Matjaz could probably discuss that aspect better than I could.
Finally, I would say that complexity isn't really one of EJBs failings at all. If anything they make the process of developing complex business objects relatively simple. Admittedly, the deployment can be a pain at times but I'm not sure if I would go so far as saying they are prohibitively complex.

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Craig Berry
Author of Professional EJB
 
Craig Berry
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Ruilin, certainly the easiest way to do it, especially if using CMP is a one-to-one bean:table mapping. EJB 2.0 introduces relationships which may help you out some. Failing that if you want more complex mapping then BMP might be the way to go - that way you can map exactly what you want to the beans, even if it takes a bit more work.

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Craig Berry
Author of Professional EJB
 
Matjaz Juric
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Well, the maturity of EJBs is always a hot topic. EJBs are still a young technology and you will have to decide how many technology related risks you are prepared to take. The fact that several large companies, including BA, are successfully using EJBs shows that the technology can be used for the prime time.
The question is also how large your project is and if EJBs are necessary. But this is already another questions.
I also agree that today there are problems with interoperability among containers. They are already being resolved - however it is also unlikely that you will try to mix the containers from different vendors.
There are also some minor problems by portability of code among app servers, but these can be resolved quickly and much easier than porting an application to a completely different architecture.
EJBs are a complex technology because they HIDE a lot of complexity from the developer. They are a complex technology in terms of developing an application server, but not in developing EJBs.
However you still have to understand the EJB concepts and the patterns you should use to get applications that perform well. With EJBs it is possible to build fast applications, but it's also possible to build slow applications too, like with any other technology.
If you do it the right way, you can build applications that offer good performance.
Cheers, Matjaz

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Matjaz Juric
Author of Professional EJB
 
Matjaz Juric
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My suggestion would be to do it the other way around. First design the application, then identify which classes you will gather into the entity beans, and only then think about how you will map the entity beans to the existing database. Otherwise you will simply do a mapping from relational to object schema, which will almost always not result in sound design.
Matjaz

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Matjaz Juric
Author of Professional EJB
 
Matjaz Juric
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Try http://java.sun.com/products/ejb/
Originally posted by yoel stern:
Hi,
I'm new to J2EE & EJB, could some tell where I can get a brief
description of it.
Thanks
Yoel


------------------
Matjaz Juric
Author of Professional EJB
 
Matjaz Juric
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No, this only means that you cannot mix application servers and containers from different vendors - but in most cases you wouldn't want to do this anyway.
Matjaz
Originally posted by Syed Hussain:
Welcome to JavaRanch.I learnt EJB sometime back, but after understanding I came to realize that there is no significant distinction made b/w an Application Server and Container defined in the EJB Specs.Is this correct.If it is, then this makes EJB platform-dependent , and thus ruining the "Java Way Of Life".
Syed.
[This message has been edited by Syed Hussain (edited September 11, 2001).]


------------------
Matjaz Juric
Author of Professional EJB
 
Tom Ben
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Thanks Craig,
Your reply has helped alot.
I am in the works now to install j2ee and get this going.
------------------
Sun Certified Programmer on the Java 2 Platform
 
Marcos Maia
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Take a look at the design patterns catalog from sun as well thats a must read to design j2ee applications:
http://java.sun.com/j2ee/blueprints/design_patterns/index.html
 
ruilin yang
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Graig,
Thanks for your last response.
At present, most people use relational database. If I chose to use a Object-orented database. Then there will not be a data mapping layer. In such case do we still need the entity bean?
Or the implementation will become very simple?
Thanks in advance.
Ruilin
 
Jorge Phillips
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Craig and Matjaz, thanks for participating in JavaRanch!
I am interested in open source EJB containers as a way of minimizing entry cost while maximizing access to container intrinsics. I also see them as advantageous in standardizing on a specific container without getting trapped by a commercial vendor through proprietary features/tricks, as you have mentioned in your posts in this forum.
I would like your advice and comments on performance and ease of deployment of enterprise java apps on open source/freeware containers as compared to commercial alternatives, say IBM Webserver or BEA Weblogic. I am thinking of JBoss/Tomcat and the like. Are there any strong reasons (aside from maintenance, support, and other anti-open source arguments) why one might want to go the commercial route with an enterprise Java application?
 
Matjaz Juric
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Open source app servers are valuable alternatives to the commercial products. Particularly JBoss is worth considering. My experience shows that it is reliable and performs well; however I haven't tested it in the production environments. I cannot give you any exact performance assessment. We are all expecting the ECperf results, which will clarify this question.
However it will have to be your decision with application server to choose. However be aware that the price of the app server is often only a small cost compared to the cost of the whole project.
Even if you choose the wrong server you will however be able to port your application to another.
Cheers,
Matjaz

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Matjaz Juric
Author of Professional EJB
 
Amit Agrawal
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I am glad that I am just in time. Actually I have recently started learning EJB but confused between different application servers.
Ok, before that I must tell about my background. I am coding in java since almost 2 years and have spent last one year mainly on jsp/servlet/oracle/apache/tomcat.
now i want to explore ejb, plz suggest me what would be best for me? weblogic or j2ee or tomcat/jboss or any other server?
I know finally its EJB that matters but It would be great, If you can suggest a good server which makes deployment easier (and transparent too, so that I can understand wats happening while I deploy my beans).
Also I would be thankful, if you could list out some links where I can easily locate resources for beginners.
Regards,
Amit.
 
James Hobson
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Hi Amit Agrawal,
In my experience Jboss-Tomcat is the easiest to get up and deploy to -- it is also reasonably small, so you can download and run it.
Also, the license ageement is nice (although I believe most appServers are free for development).
james
 
srao
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Hi,
How does BMP entity bean handle the cached data when the database it is acessing is also used by other applications, like a older client server application?
Thank you
Regards.
Sunil
 
Tom Ben
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What seems to be the best server for a Unix enviroment. I am having a really bad time with WebSphere it keeps core dumping! Any Help would be great.
------------------
Sun Certified Programmer on the Java 2 Platform
 
Scott Huddleston
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Visit: http://java.sun.com/j2ee/tutorial/ this is a good place to get a wealth of information and examples.
Scott
Originally posted by yoel stern:
Hi,
I'm new to J2EE & EJB, could some tell where I can get a brief
description of it.
Thanks
Yoel

 
Scott Huddleston
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What Unix are you speaking of? We use JRun and WebLogic on RH Linux with very good success.
Scott
Originally posted by Tom Ben:
What seems to be the best server for a Unix enviroment. I am having a really bad time with WebSphere it keeps core dumping! Any Help would be great.

 
Tom Ben
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We are running on AIX. It keeps falling all over itself. Thanks for the tip on RH Linux I just the box up and looking to run a server on it.
------------------
Sun Certified Programmer on the Java 2 Platform
 
Matjaz Juric
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Many application servers enable you to tell them whether the database is used by legacy systems too or exclusively by EJBs. Depending on the setting the container then invokes the ejbLoad() method when appropriate. The difference between BMP and CMP entity beans (from the perspective of the developer and regarding to the question) is that in CMP the ejbLoad and ejbStore methods are implemented by container, by BMP we have to implement them ourselves.
Cheers,
Matjaz
Originally posted by srao:
Hi,
How does BMP entity bean handle the cached data when the database it is acessing is also used by other applications, like a older client server application?
Thank you
Regards.
Sunil


------------------
Matjaz Juric
Author of Professional EJB
 
Mohammad Aktaruzzaman
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Hi,
I'm new to J2EE & EJB, could some tell where I can get a brief
description of it.
Thanks
Aktar

 
John Lee
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Hi:
I was wondering if we can say EJB is the hottest field in IT right now? What is the trend for java and C++?
Thanks,
Don
 
John Lee
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Hi:
I think the most popular ide for j2ee is IBM visual age. Is this correct?
Thank,
Don
 
Scott Huddleston
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Visit: http://java.sun.com/j2ee/tutorial/ this is a good place to get a wealth of information and examples.
Scott

Originally posted by Mohammad Aktaruzzaman:
Hi,
I'm new to J2EE & EJB, could some tell where I can get a brief
description of it.
Thanks
Aktar

 
Matjaz Juric
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Hi,
Visual Age for Java is a good IDE, however you might want to check at least JBuilder and Forte.
Cheers,
Matjaz
Originally posted by Don Liu:
Hi:
I think the most popular ide for j2ee is IBM visual age. Is this correct?
Thank,
Don


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Matjaz Juric
Author of Professional EJB
 
Cas Zimirs
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Craig and Matjaz, thank you for your comments.
One of the posts alluded to differences between IBM's JVM that detracts from the portability of Entity beans. Does WAS conform to the J2EE? If not, could you discuss any areas of difference and possible work-arounds?
Thanks in advance!
 
LAXMI VEMARAJU
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Can the CMP bean , allow to work with database views? or it permits only with tables? If at all it allows to work with views, then instead of BMP bean, I can as well use CMP for some transactions.
Could you make me correct.
Thanks,
Laxmi
 
Rob Acraman
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Interesting comments about the maturity of the technology. Is there a list somewhere of what major companies are currently using this technology on live systems? (esp financial systems, since I'm working in an investment bank at present that's looking/thinking about Java).
Cheers,
Rob
 
Marcos Maia
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take a look in WebGain/Visual Caf� at: www.webgain.com
it�s a great tool.
Originally posted by Don Liu:
Hi:
I think the most popular ide for j2ee is IBM visual age. Is this correct?
Thank,
Don

 
ragabo
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It is great to see such group of talented professionals.
Welcome!
 
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