Questions about EJB

I'm new to EJB.
I want to know what is ant and JBoss ?
Is ant is used to deploy ?
And what is the advantages of deploy ?
Also, is this possible to run EJB in Tomcat 4.0 ?
sorry for too many question.
Thank you !

Ant is build/compile tool (plus some). Ant can perform all kinds of tasks (javac commands, ftp, jar, etc) and is java-based (meaning you can even write your own classes to perform a task and "plug" it into Ant). Ant is capable of doing an EJB deploy.
Deployment is simply (simple in concept, not always in doing that is) the process of making the EJB or other services you create available to an app server like Weblogic or JBoss.
Tomcat is only a Servlet Container and can only be used to deploy Servlets and JSPs. To run/host EJBs, you will need to get a J2EE application server. Many free ones exist (like Resin or JBoss) as well as many commercial ones (such as Bea's Weblogic, IBM's WebSphere, and Borland's AppServer).
Hope this helps.

Similar Messages

Question about EJB and thread safe coding - asking again!

sorry everyone, no one seems to be interested in helping me on this, so i post it again.
i have a question about the EJB and thread safe coding. when we build EJBs, do we need to worry about thread safe issue? i know that EJBs are single threaded, and the container manages the thread for us. maybe i am wrong about this. if i wasnot, how can we program the EJB so that two or more instance of EJB are not going to have deadlock problem when accessing data resources. do we need to put syncronization in ours beans, do we even need to worry about creating a thread safe EJB? thanks in advance. the question really bothers me a lot lately.

sorry everyone, no one seems to be interested in
helping me on this, so i post it again.Excellent plan. Why not search a little bit on your own instead of waiting for your personal forum slaves to answer your call. See below.
i have a question about the EJB and thread safe
coding. when we build EJBs, do we need to worry about
thread safe issue? Read this: http://forum.java.sun.com/thread.jsp?forum=13&thread=562598&tstart=75&trange=15
i know that EJBs are single
threaded, and the container manages the thread for us.
maybe i am wrong about this. if i wasnot, how can we
program the EJB so that two or more instance of EJB
are not going to have deadlock problem when accessing
data resources. do we need to put syncronization in
ours beans, do we even need to worry about creating a
thread safe EJB? thanks in advance. the question
really bothers me a lot lately.
Java's Thread Tutorial
JavaWorld: Introduction to Java threads
IBM: Introduction to Java threads
Google: java+threads+tutorial

A question about EJB timeouts

Good day!
I encountered an interesting situation about EJB timer service.
1) For example, I created an implementing TimerObject Stateless Session Bean.
2) In ejbSetSessionContext method I created an timer to invoke ejbTimeout on my EJB every 15 seconds.
3) Ok. Container invokes this ejbTimeout every 15 sec. But what happens is previous ejbTimeout didn't returned because it is waiting for some connection for example. Would container invoke ejbTimeout while processing previous ejbTimeout on this one Stateless EJB?
I looked in EJB 2.1 spec. but didn't find corresponding answer.

Hi russiandroopy,
This isn't specifically mentioned in the spec because the design center of the Timer Service was not fine-grained events. The spec suggests that typical timeouts would be on the order of minutes or hours, which is typically much longer than the duration of the handling time within a timeout method or business method. In SUN's implementation we do not attempt to deliver a subsequent periodic timeout until the previous timeout completes successfully.
--ken

Questions about EJB local interfaces - 9iAS 9.03

Intro: I am new in developing EJB, and I am trying to build an example to verify that a stateless session bean with local interfaces is quite efficient.
Q1: I have read that an application trying to access local interfaces of an EJB must run into the same JVM. Does it means that it should be deployed into the same OC4J instance as the servlet?
Q2: I am using JDev 10g to build the EJB, with local and remote interfaces. Using the internal OC4J container, I can use the remote interfaces but not the internal one: an object of class "_Proxy1" is returned after the lookup (with the same name as given for the remote interface related call). Is it possible to access the local interface?
Q3: My application architecture is already defined to split the business logic in two EJBs: one stateless session bean for volatile data and one entity bean for a global user list cache. Where can I find a working example (with source code, please) to be deployed on 9iAS that can validate my design?
Q4: In many places, I read that CMP entity bean are easier to develop than BMP one. Is there any special consideration I should be aware of before implementing a CMP for my global user list cache?
Thanks a lot, Dom.

I have just read:
I think the problem is that local interfaces can only by
accessed through the same container, and JSP/Servlet's
one is different from EJB's one, regardless of you many
application server's instances do you have... Hope this
is the answer...Is there anyone who know if it applies too to 9iAS?
A+, Dom

Specification/Architectural question about EJBs and XML

Hello,
My problem is as follows: I would like for a session ejb to retrieve information from xml files (other that the ejb DDs of course...). I prefer the XML-file solution to the relational-database solution as it is more lightweight. (We haven't got the resources nor the skill to administrate a native xml database.) Am I allowed to read from the filesystem? What is the best architectural solution you would advise bearing in mind I need the information contained in the xml files to be available in java (in the session bean). Ideally I would drop xml files in a directory and they would automatically be parsed and taken into account by an ejb.
I am available to provide more details if needed.
Any clue welcome,
Julien Martin.

Hello,
My problem is as follows: I would like for a session ejb to retrieve information from xml files (other that the ejb DDs of course...). I prefer the XML-file solution to the relational-database solution as it is more lightweight. (We haven't got the resources nor the skill to administrate a native xml database.) Am I allowed to read from the filesystem? What is the best architectural solution you would advise bearing in mind I need the information contained in the xml files to be available in java (in the session bean). Ideally I would drop xml files in a directory and they would automatically be parsed and taken into account by an ejb.
I am available to provide more details if needed.
Any clue welcome,
Julien Martin.

Pls help - Syntax question about EJB QL

Hello,
I'm new learner on EJB. I went through the specification 2.0 of EJB QL released by Sun, I'm not quite understand the syntax definition of SELECT clause in finder method which described in the following words:
"In the case of a find method, the SELECT clause is restricted to contain either a single range variable or a single value path expression that evaluates to the abstract schema type of the entity bean for which the finder method is defined.
Because finder method cannot return arbitrary types, the SELECT clause of an EJB QL defined for a finder method must always correspond to the abstract shcema type fo the entity bean for which the finder method is defined.In contrast, the SELECT clause of a query defined for a select method can return the abstract schema types of other entity beans or the values of cmp-fields."
As my understanding, I think the SELECT clause of finder method can only contain a single range variable instead of single value path expresson, it should have only one format, which is "SELECT [DISTINCT] OBJECT(identification_variable)".
For example: the query below is defined in OrderBean findByProductType();
SELECT OBJECT(o) FROM Order o, IN(o.lineItems) l
WHERE l.product.product_type = 'schoolsupplies'
how it could be a single value path expression , I think this format can only be used in Select method.
The other thing is EJB QL2.0 does not support subquery and "NOT EXIST" clause, does this mean that a SQL query with subquery or "NOT EXIST" clause can't be translated to EJB QL?
I don't know if I'm correct or not. I'd appreciate if anybody can help me with this.
Thanks!
Maggie

Hi,
Weblogic
=======
In the Weblogic-cmp-rdbms-jar.xml file, we define the Table name as created in the DBMS along with cmp-field mapped to the dbms-columns of the table as described below
<table-map>
<table-name>SalesAccounts</table-name>
<field-map>
<cmp-field>salesaccountId</cmp-field>
<dbms-column>sales_acctid</dbms-column>
</field-map>
<field-map>
<cmp-field>salesbalance</cmp-field>
<dbms-column>sales_bal</dbms-column>
</field-map>
<field-map>
<cmp-field>salesaccountType</cmp-field>
<dbms-column>sales_type</dbms-column>
</field-map>
</table-map>
Here SalesAccounts is the actual table defined in DBMSD like Oracle say which has columns sales_acctid, sales_bal and sales_type.
In ejb-jar.xml, you define an abstract schema name ie some sort of alias for your table name (SalesAccounts) along with defining the cmp fields required for writing a EJB-QL.
<abstract-schema-name>SalesAccountBean</abstract-schema-name>
<cmp-field><field-name>salesaccountId</field-name>
</cmp-field>
<cmp-field><field-name>salesbalance</field-name>
</cmp-field>
<cmp-field><field-name>salesaccountType</field-name>
</cmp-field>
<primkey-field>salesaccountId</primkey-field>
Here salesaccountid is defined as a Primary key.
Now your EJB-QL can be defined in the ejb-jar.xml file as follows
<query>
<query-method>
<method-name>findSalesAccountsCondition</method-name>
<method-params>
<method-param>double</method-param>
</method-params>
</query-method>
<ejb-ql>
<![CDATA[SELECT OBJECT(a) FROM SalesAccountBean AS a WHERE a.salesbalance > ?1]]>
</ejb-ql>
</query>
This should clear ur doubts. Case u have any, revert back to me.
Rgds,
Seetesh

Question about EJB

my architecture: servlet->EJB
Why i have to use ejb instead a simplier object.
When i really nead to use EJB?
Thanks
valefr

Hi,
Ya, obviously u can use ur own classes to work the way the ejb work, but it will be a tedious task.. How will u take care of security, transaction management, persistance of data and so on...Y u can do all by urself but it will be a too lengthy process. U can use EJB instead to do all thes things for u. I mean the EJB server does it for u.Hope this clarifies ur doubt..
Ebistro

Question about EJB and Poject Management for a Company

In my Company we have some problems with the management of Java Projects and
EJB Projects. Alot of code is not reused but written again, cause noone manages it.
Are there any programs or guides (guidelines) who can support us with these problems?
How do you handle these problems?
Thanks

In my Company we have some problems with the
management of Java Projects and
EJB Projects. Alot of code is not reused but written
again, cause noone manages it.
Are there any programs or guides (guidelines) who can
support us with these problems?
How do you handle these problems?I guess you should take a look at core J2EE patterns during the design. :)
http://java.sun.com/blueprints/corej2eepatterns/Patterns/index.html

Question about EJB deployment (NoClassDefFoundError)

I got a "NoClassDefFoundError" when I bring up my servlet which tries
to use a session bean. Can anyone tell me the correct way to deploy
EJB in web logic 6.1?
My case is:
I have a session bean "examples.mysession" packaged in examples.jar
and
stored in "<wl dir>/config/mydomain/applications".
In addition, I create an application "testapp" with a number of jsp &
servlets.
("<wl dir>/config/mydomain/applications/testapp")
The servlets' classes are stored in
"<wl dir>/config/mydomain/applications/testapp/WEB-INF/classes/examples/myservlet.class"
In the servlet, I am trying to use the mysession bean by calling
"create()" on mysession's home object. This is where I got the
"NoClassDefFoundError".
java.lang.NoClassDefFoundError: examples/mysession
at java.lang.Class.newInstance0(Native Method)
at java.lang.Class.newInstance(Class.java:237)
Is there something missing in my deployment procedure?
Thanks in advance

ClassNotFound exception for the ejb interfaces while accessing from servlet
http://support.bea.com/askbea/wls/S-07398.html
Terrence Leung wrote:
I got a "NoClassDefFoundError" when I bring up my servlet which tries
to use a session bean. Can anyone tell me the correct way to deploy
EJB in web logic 6.1?
My case is:
I have a session bean "examples.mysession" packaged in examples.jar
and
stored in "<wl dir>/config/mydomain/applications".
In addition, I create an application "testapp" with a number of jsp &
servlets.
("<wl dir>/config/mydomain/applications/testapp")
The servlets' classes are stored in
"<wl dir>/config/mydomain/applications/testapp/WEB-INF/classes/examples/myservlet.class"
In the servlet, I am trying to use the mysession bean by calling
"create()" on mysession's home object. This is where I got the
"NoClassDefFoundError".
java.lang.NoClassDefFoundError: examples/mysession
at java.lang.Class.newInstance0(Native Method)
at java.lang.Class.newInstance(Class.java:237)
Is there something missing in my deployment procedure?
Thanks in advance

Know about EJB.

Hi,
I dont have any idea about EJB and also how the EJB is differ from java beans.
Thanks in advance.

Romain - I think the answer to your question is that the information
identifying the user is passed into the initial context parameters. Weblogic
uses this to propagate the security context from the servlet container to
the ejb container.
cheers,
Markus
"romain" <[email protected]> wrote in message
news:3b0e8b23$[email protected]..
>
Hi
perhaps it is a dummy question but I didn't find any explicit answer.
I'd like to know how the ejb can know if a user belongs to a role.
For example if I want to access my ejb with a servlet, and this servlet isprotected
(access allowed only for group customer)
and in my bean's deployment descriptor I have protected one method withthe security
role customer)
What I am wondering is when the user is authenticated in the servlet as acustomer
and then try to access the method how the ejb knows that this user is inthe group
customer??
Is this information included in the http session or in the initialcontextcreated
in the servlet or somewhere else??
thanks for your help
romain

About EJB 3.0 ?

i don't know anything about EJB (nither EJB 3.0 nor any previous version )
i want to learn EJB 3.0, but the final version of 3.0 EJB 3.0 has not been release.
i have heard that in EJB 3.0 all the old concepts have been changed.
a) will it be a good idea to start learning the latest version (version prior to 3.0)
and to get familiar with EJB and then later upgrade ?
or
b) wait for the EJB 3.0 and start learning EJB 3.0 only when its final version comes
please give me a helpful suggestion

This is a late feedback on your question but now JSR220: EJB 3.0 now is in its "Proposed Final Draft" stage.
http://java.sun.com/products/ejb/docs.html
I feel that starting afresh with EJB 3.0 is not a bad idea because there are some major changes in the way EJBs will be developed in future.
Knowing EJB 2.x is always a plus and you would certainly appreciate the new incarnation for its simplicity.
Hope this helps.
Cheers,
-_.

Question about using Runtime.getRuntime();

hi all
i have a question about using Runtime.getRuntime(). if i use this to get a runtime reference to run an external program, is it considered as starting a new thread inside the thread that starts it?
is it safe to do it in the Session EJB? if not, what can you recommand to do it? thanks

hi all
i have a question about using Runtime.getRuntime().
if i use this to get a runtime reference to run an
external program, is it considered as starting a new
thread inside the thread that starts it? No. Starting a process, starts a process. Threads have nothing to do with it.
is it safe to do it in the Session EJB? if not, what
can you recommand to do it? thanksSo what? Run another process? If you want to run another process in java then your choices are to use Runtime.exec() or use JNI. And using JNI will probably end up doing exactly the same thing as Runtime.exec().
"Safe" is harder. Typically to correctly use Runtime.exec() you must use threads. And as noted threads ideally should not be used. You can use them but if you do you had better understand why they didn't want you using them in the first place. You had also better be sure that you really want to wait for it to complete.
Other than that Runtime.exec() is safe because it can't crash the VM like other interfaces can (like JNI.)

Questions about your new HP Products? HP Expert Day: January 14th, 2015

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We will be holding more of these Expert Days on different topics in the months to come. We hope to see you then!
If you still have questions to ask, feel free to post them on the Forum – we always have experts online to help you out.
So, what is HP Expert Day?
Expert Day is an online event when HP employees join our Support Forums to answer questions about your HP products. And it’s FREE.
Ok, how do I get started?
It’s easy. Come out to the HP Support Forums, post your question, and wait for a response! We’ll have experts online covering our Notebook boards, Desktop boards, Tablet boards, and Printer and all-in-one boards.
We’ll also be covering the commercial products on the HP Enterprise Business Community. We’ll have experts online covering select boards on the Printing and Digital Imaging and Desktops and Workstations categories.
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Enterprise Business Forum: January 14th 7:00am to 12:00pm and 6:00pm to 11:00pm Pacific Time
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Looking forward to seeing you on January 14th!
I am an HP employee.

My HP, purchased in June 2012, died on Saturday. I was working in recently installed Photoshop, walked away from my computer to answer the phone and when I came back the screen was blank. When I turned it on, I got a Windows Error Recovery message. The computer was locked and wouldn't let me move the arrow keys up or down and hitting f8 didn't do anything.
I'm not happy with HP. Any suggestions?

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Questions about using the Voice Memos app

I'm currently an Android user, but will be getting an iPhone 6 soon. My most used app is the voice memos app on my Android phone. I have a couple questions about the iPhone's built-in voice memos app.
-Am I able to transfer my voice memos from my Android phone to my iPhone, so my recordings from my Android app will show up in the iPhone's voice memos app?
-When exporting voice memos from the iPhone to computer, are recordings in MP3 format? If not, what format are they in?
-In your opinion, how is the recording quality of the voice memos app?

You cannot import your Android voice memos to your iPhone's voice memo app. You might be able to play the Android memos and have the iPhone pick up the audio and record it.
Here is the writeup about sending voice memos from the iPhone to your computer (from the iPhone User Guide):
App quality is excellent.

Questions about EJB

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