Using EJB in XI

Hi.
1) how can i use EJB in XI ?
2) in what way java proxy , webservices ...?
3) must i use BPM for that?
thanks.
motty.

Hi,
>>>>2) in what way java proxy , webservices ...?
java proxy
>>>3) must i use BPM for that?
no
Regards,
michal

Similar Messages

A Tip for using EJB 3.0 with WebLogic Ant Tasks

I started out writing this up as a problem, but then I found the answer so I'm, posting a tip instead.
When I tried to write an EJB [stateless] using EJB 3.0 in my legacy Weblogic ear project I started getting this error:
<pre>
No EJBs found in the ejb-jar file 'test'. Please ensure the ejb-jar contains EJB declarations via an ejb-jar.xml deployment descriptor or at least one class annotated with the @Stateless, @Stateful or @MessageDriven EJB annotation.
</pre>
This is why: wlcompile will put the class files in the App-Inf/classes directory unless it finds an ejb-jar.xml file in the META-INF directory for the module it is working on. With EJB 3.0, I wasn't using an ejb-jar.xml file because it was unnecessary. Later, Appc runs and it complains because there are no classes module directory, they went into the shared ear folder instead.
Here's I how it working again: Use javac [not wlcompile] to compile the EJB 3.0 module and make sure that the class files go into the correct module directory. Then you can use wlappc to generate all the associated files for the EJB. I have sucessfully deployed an ear file that uses both EJB 2.x and EJB 3.0 with this approach.
I wish Weblogic's own ejb3.0 sample application used their split directory deployment.
Good Luck.
John Aronson

Hi John,
I am working on development an enterprise application using EJB 3.0 on Weblogic 10.
While developing, I am keeping all my classes (from ejb's as well as web) into APP-INF/classes directory. It is working fine for Web and ejb 2.0 packages, but ejb 3.0 packages, I get the following error when I keep my ejb 3.0 beans classes in APP-INF/classes directory.
No EJBs found in the ejb-jar file 'customer'. Please ensure the ejb-jar contains EJB declarations via an ejb-jar.xml deployment descriptor or at least one class annotated with the @Stateless, @Stateful or @MessageDriven EJB annotation.
One solution is to keep the classes under customer ejb directory, but I wan tto keep all the classes in APP-INF/classes directory so that when using Eclipse IDE I can output all compiled sources into APP-INF/classes directory.
Has anyone faced this situation? Any suggestions to fix this issue?

How can I use EJB component on Weblogic 8.1 server ?

hi,dear sir:
How can I use EJB component on Weblogic 8.1 server ?
It need client jar to invoke ejb,but what will I to do for this jar file? what does it contain? format ?
If my EJB module contain 100 session bean and 50 Entity bean,but I want invoke 20 session beans in my module, how can I to do?
thank you...

Hi,
This forum is exclusively for Creator. please post this on appropriate forum
regards
CreatorTeam

How can I develop a web application using EJB design pattern?

I have searched over the web and found quite a lot of tutorials on how to use the EJB design pattern.
I know that there will be a home interface, EJB object interface and a SessionBean.
But the tutorials often only cover a single class, this made me unable to get a complete picture of how EJB design pattern can be implemented into a whole system.
I am now required to devleop an online shopping web application using EJB and JSP page.
I think I will need to create a lot of classes: Member, ShoppingCart, Product...etc.
What I want to ask is that, do I need to create a home interface, EJB object interface and a SessionBean for each of these classes?
I really need some ideas on how to develop this system using EJB + JSP pages.
Many thanks to you all.

For every EJB that you want to create, you will need to code a home and remote interface and a bean class.
You could start getting your ideas here
http://www.theserverside.com/books/wiley/masteringEJB/
http://www.coreservlets.com

I need a clarification : Can I use EJBs instead of helper classes for better performance and less network traffic?

My application was designed based on MVC Architecture. But I made some changes to HMV base on my requirements. Servlet invoke helper classes, helper class uses EJBs to communicate with the database. Jsps also uses EJBs to backtrack the results.
I have two EJBs(Stateless), one Servlet, nearly 70 helperclasses, and nearly 800 jsps. Servlet acts as Controler and all database transactions done through EJBs only. Helper classes are having business logic. Based on the request relevant helper classed is invoked by the Servlet, and all database transactions are done through EJBs. Session scope is 'Page' only.
Now I am planning to use EJBs(for business logic) instead on Helper Classes. But before going to do that I need some clarification regarding Network traffic and for better usage of Container resources.
Please suggest me which method (is Helper classes or Using EJBs) is perferable
1) to get better performance and.
2) for less network traffic
3) for better container resource utilization
I thought if I use EJBs, then the network traffic will increase. Because every time it make a remote call to EJBs.
Please give detailed explanation.
thank you,
sudheer

Please suggest me which method (is Helper classes or Using EJBs) is perferable :
1) to get better performance
EJB's have quite a lot of overhead associated with them to support transactions and remoteability. A non-EJB helper class will almost always outperform an EJB. Often considerably. If you plan on making your 70 helper classes EJB's you should expect to see a dramatic decrease in maximum throughput.
2) for less network traffic
There should be no difference. Both architectures will probably make the exact same JDBC calls from the RDBMS's perspective. And since the EJB's and JSP's are co-located there won't be any other additional overhead there either. (You are co-locating your JSP's and EJB's, aren't you?)
3) for better container resource utilization
Again, the EJB version will consume a lot more container resources.

How to Retrive data from db using EJB in WebDynpro

hi...
i m using EJB's for backend connection in WebDynpro .in which i m able to store data in sapdb .for this i followed one tutorial which i have mentioned bellow which works perfectly.Now in the same Tutorial i want to retrive the data from database and disply it in WebDynpro
i .e i want to disply bonus when i give ssn no and also i want to disply all data in db.
Please help me as i m totaly new to this environment and also first time i m working on EJB.its very urgent
Thanks and Regards
Sonal<a href="https://www.sdn.sap.comhttp://www.sdn.sap.comhttp://www.sdn.sap.com/irj/servlet/prt/portal/prtroot/docs/library/uuid/1f5f3366-0401-0010-d6b0-e85a49e93a5c">https://www.sdn.sap.comhttp://www.sdn.sap.comhttp://www.sdn.sap.com/irj/servlet/prt/portal/prtroot/docs/library/uuid/1f5f3366-0401-0010-d6b0-e85a49e93a5c</a>

hi...
i m using EJB's for backend connection in WebDynpro .in which i m able to store data in sapdb .for this i followed one tutorial which i have mentioned bellow which works perfectly.Now in the same Tutorial i want to retrive the data from database and disply it in WebDynpro
i .e i want to disply bonus when i give ssn no and also i want to disply all data in db.
Please help me as i m totaly new to this environment and also first time i m working on EJB.its very urgent
Thanks and Regards
Sonal<a href="https://www.sdn.sap.comhttp://www.sdn.sap.comhttp://www.sdn.sap.com/irj/servlet/prt/portal/prtroot/docs/library/uuid/1f5f3366-0401-0010-d6b0-e85a49e93a5c">https://www.sdn.sap.comhttp://www.sdn.sap.comhttp://www.sdn.sap.com/irj/servlet/prt/portal/prtroot/docs/library/uuid/1f5f3366-0401-0010-d6b0-e85a49e93a5c</a>

Could not lookup PortalManagerHome in the JNDI tree using EJB reference java:comp/env/ejb/PortalManager

Hi
I am just a starter on WLPortal.
I have created a barebone Application from scratch. I have synchronized it properly
from EBCC to WLP. But When I am trying to access the home page of my application,
I am getting from stack trace -
<Nov 6, 2002 5:37:59 PM IST> <Error> <PortalAppflow> <Could not lookup PortalManagerHome
in the JNDI tree using EJB reference java:comp/env/ejb/PortalManager.
javax.naming.NameNotFoundException: Unable to resolve comp/env/ejb/PortalManager
Resolved: 'comp/env' Unresolved:'ejb' ; remaining name 'PortalManager'
at weblogic.jndi.internal.BasicNamingNode.newNameNotFoundException(BasicNamingNode.java:802)
at weblogic.jndi.internal.BasicNamingNode.lookupHere(BasicNamingNode.java:209)
at weblogic.jndi.internal.BasicNamingNode.lookup(BasicNamingNode.java:173)
at weblogic.jndi.internal.BasicNamingNode.lookup(BasicNamingNode.java:181)
at weblogic.jndi.internal.BasicNamingNode.lookup(BasicNamingNode.java:181)
at weblogic.jndi.internal.WLContextImpl.lookup(WLContextImpl.java:323)
at weblogic.jndi.factories.java.ReadOnlyContextWrapper.lookup(ReadOnlyContextWrapper.java:36)
at weblogic.jndi.internal.AbstractURLContext.lookup(AbstractURLContext.java:124)
at javax.naming.InitialContext.lookup(InitialContext.java:350)
at com.bea.p13n.util.JndiHelper.lookupNarrow(JndiHelper.java:96)
at com.bea.portal.appflow.PortalAppflowHelper.<clinit>(PortalAppflowHelper.java:64)
at com.bea.portal.appflow.servlets.internal.PortalWebflowServlet.init(PortalWebflowServlet.java:78)
at javax.servlet.GenericServlet.init(GenericServlet.java:258)
at weblogic.servlet.internal.ServletStubImpl.createServlet(ServletStubImpl.java:700)
at weblogic.servlet.internal.ServletStubImpl.createInstances(ServletStubImpl.java:643)
at weblogic.servlet.internal.ServletStubImpl.prepareServlet(ServletStubImpl.java:588)
at weblogic.servlet.internal.ServletStubImpl.getServlet(ServletStubImpl.java:368)
at weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:242)
at weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:200)
at weblogic.servlet.internal.RequestDispatcherImpl.forward(RequestDispatcherImpl.java:215)
at weblogic.servlet.jsp.PageContextImpl.forward(PageContextImpl.java:112)
at jsp_servlet.__index._jspService(__index.java:92)
at weblogic.servlet.jsp.JspBase.service(JspBase.java:27)
at weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:265)
at weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:304)
at weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:200)
at weblogic.servlet.internal.WebAppServletContext.invokeServlet(WebAppServletContext.java:2459)
at weblogic.servlet.internal.ServletRequestImpl.execute(ServletRequestImpl.java:2039)
at weblogic.kernel.ExecuteThread.execute(ExecuteThread.java:139)
at weblogic.kernel.ExecuteThread.run(ExecuteThread.java:120)
>
<Nov 6, 2002 5:37:59 PM IST> <Error> <HTTP> <[WebAppServletContext(19695286,FirstWebApp,/FirstWebApp)]
Servlet failed with Exception
java.lang.NullPointerException:
at com.bea.portal.appflow.PortalAppflowHelper.createPortalManager(PortalAppflowHelper.java:82)
at com.bea.portal.appflow.servlets.internal.PortalWebflowServlet.setupPortalRequest(PortalWebflowServlet.java:187)
at com.bea.portal.appflow.servlets.internal.PortalWebflowServlet.doGet(PortalWebflowServlet.java:99)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:740)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:265)
at weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:200)
at weblogic.servlet.internal.RequestDispatcherImpl.forward(RequestDispatcherImpl.java:215)
at weblogic.servlet.jsp.PageContextImpl.forward(PageContextImpl.java:112)
at jsp_servlet.__index._jspService(__index.java:92)
at weblogic.servlet.jsp.JspBase.service(JspBase.java:27)
at weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:265)
at weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:304)
at weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:200)
at weblogic.servlet.internal.WebAppServletContext.invokeServlet(WebAppServletContext.java:2459)
at weblogic.servlet.internal.ServletRequestImpl.execute(ServletRequestImpl.java:2039)
at weblogic.kernel.ExecuteThread.execute(ExecuteThread.java:139)
at weblogic.kernel.ExecuteThread.run(ExecuteThread.java:120)
When I decompiled the class PortalAppflowHelper, I found a static block in it,
which was as under-
static
debug = Debug.getInstance(com.bea.portal.appflow.PortalAppflowHelper.class);
try
if(debug.ON)
debug.out("Looking up PortalManagerHome using EJB reference java:comp/env/ejb/PortalManager");
portalManagerHome = (PortalManagerHome)JndiHelper.lookupNarrow("java:comp/env/ejb/PortalManager",
com.bea.portal.manager.ejb.PortalManagerHome.class);
if(debug.ON)
debug.out("Successfully retrieved PortalManagerHome " + portalManagerHome);
catch(Exception e)
PortalAppflowLogger.errorFindingPortalManagerHome("java:comp/env/ejb/PortalManager",
e);
I have checked the PortalManager's JNDI name on WLConsole. Its ${APPNAME}.BEA_portal.PortalManager.
Should I change it?
When I tried to change it, I started getting other weird errors.
Thanks
Neeraj Hans

Neeraj -
The Portal framework code (including PortalAppflowHelper) uses ejb
references to find the PortalManager (and other EJBs) from servlets and
taglibs; that is what is signified by the java:comp/env/... name.
Since you built your webapp from scratch (instead of using the portal
wizard), you will need to make sure the you have the appropriate
<ejb-ref> entries in your web.xml, and the corresponding
<ejb-reference-description> entries in your weblogic.xml. By default,
you will need at least mappings for:
- ejb/PortalManager
- ejb/UserManager
- ejb/GroupManager
- ejb/PipelineExecutor
- ejb/EventService
See either the resulting webapp from using the portal wizard or
BEA_HOME/weblogic700/samples/portal/sampleportalDomain/beaApps/sampleportal/sampleportal/WEB-INF
for example syntax.
Greg
Neeraj Hans wrote:
Hi
I am just a starter on WLPortal.
I have created a barebone Application from scratch. I have
synchronized it properly
from EBCC to WLP. But When I am trying to access the home page of my
application,
I am getting from stack trace -
<Nov 6, 2002 5:37:59 PM IST> <Error> <PortalAppflow> <Could not lookup
PortalManagerHome
in the JNDI tree using EJB reference java:comp/env/ejb/PortalManager.
javax.naming.NameNotFoundException: Unable to resolve
comp/env/ejb/PortalManager
Resolved: 'comp/env' Unresolved:'ejb' ; remaining name 'PortalManager'
at <stack trace lines snipped>
When I decompiled the class PortalAppflowHelper, I found a static
block in it,
which was as under-
static
debug =
Debug.getInstance(com.bea.portal.appflow.PortalAppflowHelper.class);
try
if(debug.ON)
debug.out("Looking up PortalManagerHome using EJB
reference java:comp/env/ejb/PortalManager");
portalManagerHome =
(PortalManagerHome)JndiHelper.lookupNarrow("java:comp/env/ejb/PortalManager",
com.bea.portal.manager.ejb.PortalManagerHome.class);
if(debug.ON)
debug.out("Successfully retrieved PortalManagerHome "
+ portalManagerHome);
catch(Exception e)
PortalAppflowLogger.errorFindingPortalManagerHome("java:comp/env/ejb/PortalManager",
e);
I have checked the PortalManager's JNDI name on WLConsole. Its
${APPNAME}.BEA_portal.PortalManager.
Should I change it?
When I tried to change it, I started getting other weird errors.
Thanks
Neeraj Hans

Error while retreiving data from oracle using EJB.

HII All,
I m getting this error while trying to retreive data from oracle DB using EJB.
An error has occurred. Maybe the request is not accepted by the server:
Exception in method empName.
HTTP/1.1 500 Internal Server Error
Connection: close
Server: SAP J2EE Engine/6.40
Content-Type: text/xml; charset=UTF-8
Set-Cookie: <value is hidden>
Date: Mon, 24 Jul 2006 10:50:11 GMT
<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" ><SOAP-ENV:Body><SOAP-ENV:Fault><faultcode>SOAP-ENV:Client</faultcode><faultstring>Exception in method empName.</faultstring><detail><ns1:com.sap.engine.services.ejb.exceptions.BaseEJBException xmlns:ns1='http://sap-j2ee-engine/client-runtime-error'>Exception in method empName.</ns1:com.sap.engine.services.ejb.exceptions.BaseEJBException></detail></SOAP-ENV:Fault></SOAP-ENV:Body></SOAP-ENV:Envelope>
Thanks in advance
Devendra Phate.

Hi Devendra,
this error message does not tell me much. Pleas either start debugging or watch your logs for more detailed messages.
Regards,
Benny

Error during deployment of stateless session EJB using EJB 3.0

having trouble deploying a stateless session bean to app server 10.1.3.1 oc4j container.
deceided to go through oracles demo: How-To Develop a Stateless Session EJB using EJB 3.0 (http://www.oracle.com/technology/tech/java/oc4j/1013/how_to/how-to-ejb30-stateless-ejb/doc/how-to-ejb30-stateless-ejb.html).
the demo encounters the same issue. so i assume there is something wrong with the app server set up, and not my source code.
here is the deployment log:
[Jul 1, 2009 11:59:25 AM] Application Deployer for test_ws STARTS.
[Jul 1, 2009 11:59:25 AM] Copy the archive to C:\product\10.1.3.1\OracleAS_1\j2ee\home\applications\test_ws.ear
[Jul 1, 2009 11:59:25 AM] Initialize C:\product\10.1.3.1\OracleAS_1\j2ee\home\applications\test_ws.ear begins...
[Jul 1, 2009 11:59:25 AM] Unpacking test_ws.ear
[Jul 1, 2009 11:59:25 AM] Done unpacking test_ws.ear
[Jul 1, 2009 11:59:25 AM] Initialize C:\product\10.1.3.1\OracleAS_1\j2ee\home\applications\test_ws.ear ends...
[Jul 1, 2009 11:59:25 AM] Starting application : test_ws
[Jul 1, 2009 11:59:25 AM] Initializing ClassLoader(s)
[Jul 1, 2009 11:59:25 AM] Initializing EJB container
[Jul 1, 2009 11:59:25 AM] Loading connector(s)
[Jul 1, 2009 11:59:26 AM] Starting up resource adapters
[Jul 1, 2009 11:59:26 AM] Processing EJB module: ejb30ws-ejb.jar
[Jul 1, 2009 11:59:26 AM] application : test_ws is in failed state
[Jul 1, 2009 11:59:26 AM] Operation failed with error: java.lang.NoClassDefFoundError
the opmn log reveals the same error, but no more detail.
any ideas???
/stuck

I am having exactly the same issue. Was this issue resolved? If so, please share the resolution and if not can someone please suggest what could be wrong.
Thanks

Performing database operations using EJB 3.0

I need to create a session bean that will perform operations on backend database. I am new to EJB 3.0 and need a gentle guidance to the solution
This is what I believe is suppose to be done
1. Create stateless bean interface marking operations.
2. Create bean implementation for above
3. Init stage will require me to connect to the Oracle database. Now am confused how will it get the connection details? Is there a way to extract the url username and password using resource bendle which can be accessed from within bean implementation?
4. Bean method will perform update, read oprations
5. Predestroy will close the connection
6. A client will simply call this ejb with some input parameter(s)
Please let me know if am doing anything wrong here

If you use EJB technology for which it is designed, the container (server) will manage the transaction (and also the connections to the database) for you, so no creation or cleanup of connections on your part. I advise you to read into JPA which is designed to be used in conjunction with EJB tech. The books Enterprise Javabeans 3.0 and Pro EJB 3: the Java Persistence API may help you a lot.

Problem with "package-info.java" using EJB 3.0 and OC4J

Hi all.
I already posted this question on JDeveloper forum, but didn't get any answer,
so I'll try posting here.
Anyway, I'm new both to JDeveloper and J2EE,
so I'm trying out examples for EJB 3.0, and I got stuck at "Use Security Annotations with EJB 3.0"
(http://www.oracle.com/technology/tech/java/oc4j/ejb3/howtos-ejb3/howtoejb30security/doc/how-to-ejb30-security-ejb.html).
Example code is working perfectly, if one builds it using Ant, but I'm importing all examples into JDeveloper (or at least I'm trying to :))
JDeveloper can't build file "package-info.java" containing following code:
@javax.annotation.security.SecurityRoles(roleNames={"superuser", "user"})
package oracle.ejb30;I'm getting following output in "Compiler - Log" window:
Error(2,1): 'class', 'interface', or 'enum' expected.
Help much appreciated...
platform used:
Windows XP SP2
JDeveloper Studio (Version 10.1.3, Build 3412)
JDK 1.5_06
OC4J 10.1.3 developer preview 4 (standalone version)

Since you're using EJBs, you can use JTA and can skip the getTransaction() calls. If you want to use getTransaction().begin() and commit(), then make sure that your EntityManager is resource-local. The configuration for this is in persistence.xml. Set a transaction-type of RESOURCE_LOCAL rather than JTA.

How to start and finish a transaction using EJB 3.0 in JDeveloper

Hello everybody!
Does anybody can explain how to start and finish a transaction using EJB 3.0. I need to start a transaction insert some information in some tables and if everything was fine commit the information.
I put the annotation @TransactionManagement(TransactionManagementType.BEAN) in my session bean and @Resource SessionContext ejbContext; but I don't what anything else I have to do.
Any help will be appreciate.

I tryied to use in the client the statement EntityTransaction transaction = myBean.getTransact(); but I receive the EJBException: Cannot use resource level transactions with a container managed EntityManager
I just need to start a transaction something like this: transaction.begin(); and finish the transaction, something like this: transaction.commit();
Does anybody can help?

Using local session bean interface from web container using EJB 3.0

Hi,
How can you use a local session bean interface from Java (rather than data controls) in a web container using EJB 3.0?
I can use a remote interface by looking up InitialContext, but I can't find a local interface this way (even from another session EJB). I can use a local interface from an EJB using annotation "EJB", but as I understand, this is not available in the web container.
If I try to add an ejb-jar.xml file, these seems to mess up by project...
Hope you can help.
Roger

The portable way to retrieve an EJB reference in Java EE is to either inject it or look it up via the
component's private naming environment. The simplest way is :
@EJB
private DocumentManager dm;
The global JNDI name is only used as an implementation specific way to uniquely assign an
identifier to a specific Remote EJB. It's best for this not to appear directly in the source code.
There's more on global JNDI names in our EJB FAQ :
https://glassfish.dev.java.net/javaee5/ejb/EJB_FAQ.html
The alternative to annotations is to use an ejb-ref to declare the ejb dependency. The ejb-ref
is declared in the standard deployment descriptor corresponding to the component doing the
lookup. Each ejb-ref has an ejb-ref-name, e.g. <ejb-ref-name>DM_ref</ejb-ref-name>
The code looks up the ejb-ref-name relative to the java:comp/env namespace to retrieve the
EJB reference.
DocumentManager dm = (DocumentManager)
new InitialContext().lookup("java:comp/env/DM_ref");

How to load data in plain-text file into database by using EJB?

Hi,
We need to develop an on-line application which requires us to load input data
from a selected plain-text file on the Web server (iplanet server) into the backend
oracle database. How could I use EJB to make it happen? it seems like using Entity
EJB is not feasible.
Really appreciate your help!
Corona

Hi Corona,
"Corona Fang" <[email protected]> wrote in message
news:3f3b0ea3$[email protected]..
We need to develop an on-line application which requires us to load inputdata
from a selected plain-text file on the Web server (iplanet server) intothe backend
oracle database. How could I use EJB to make it happen? it seems likeusing Entity
EJB is not feasible.If you are talking about loading thousands of records,
the preferable way is using plain JDBC calls utilizing
batch methods.
Regards,
Slava Imeshev

How to use ejbs for accessing Function Module.

Hi,
I want to call ABAP function module using ejb(Since I want to expose them as web service on different server). I know how to do that using Models, but dont know how to go ahead using ejbs.
Could you please guide me on this?
Regards,
Abhijeet.

Hi,
In another thread with a similar question I found these references:
/people/kathirvel.balakrishnan2/blog/2005/07/26/remote-enable-your-rfchosttoip-to-return-host-ip-to-jco
Re: interfacing SAP with an existing java applications
And this code example:
 HashMap result = new HashMap();
 Object ret = new Object();
 JCO.Client mConnection = null;
 mConnection = getConnection();
 JCO.Repository mRepository;
 mRepository = new JCO.Repository("R3", mConnection);
 JCO.Function function =
 createFunction("Z_ISA_GET_ORDER_ITEM_INFO", mRepository);
 function.getImportParameterList().setValue(orderNum, "ORDER");
 if (function != null) {
 mConnection.execute(function);
 JCO.Table codes = function.getTableParameterList().getTable("INFO");
 for (int i = 0; i < codes.getNumRows(); i++) {
 codes.setRow(i);
 int tmp = new Integer(codes.getString("POSNN")).intValue();
 String tmpStr = new String(Integer.toString(tmp));
 ret = result.put(tmpStr, codes.getString("VBELN"));
 } else {
 System.out.print("Fxn call failed for Z_ISA_GET_ORDER_ITEM_INFO");
 JCO.releaseClient(mConnection);
Good luck,
Roelof

Using EJBs in Web Dynpro

I have recently started to develop Web applications using the Web Dynpro framework. Coming from a pure J2EE world, I must admit that Web Dynpro has a few innovative features that I find interesting for user interface development. The use of component & view contexts, for example, is not unlike the ActionForms that one may find in a Struts application, but pushed a bit further. No complaints here.
What I do have some problems with is the whole CommandBean paradigm that is put forth by SAP (refer to the document <a href="https://www.sdn.sap.comhttp://www.sdn.sap.comhttp://www.sdn.sap.com/irj/servlet/prt/portal/prtroot/com.sap.km.cm.docs/library/webdynpro/using%20ejbs%20in%20web%20dynpro%20applications.pdf">Using EJBs in Web Dynpro</a>).
I do understand the usefulness of defining a model that will be used to generate and eventually bind to Context data structures. That's fine. What I do object to is the use of a so-called CommandBean to play that role. Again, coming from a J2EE world, I am familiar with the BusinessDelegate pattern - which would typically be used by a client application to invoke business logic on the server side. I would propose that a better, cleaner way of integrating EJBs with the Web Dynpro framework would be to use a BusinessDelegate for invoking business logic, and importing a separate and distinct ModelBean (instead of a CommandBean) to be used for defining and binding to Context data.
I have built one Web Dynpro application thus far. Instead of using a CommandBean, I created a ModelBean that extends my business object DTO (Data Transfer Object) (which is quite appropriate for that role, given that it implements all the get & set methods that are required for the business data that I need to model). My Web Dynpro application also makes use of an independant BusinessDelegate that is packaged with my EJB DC - this is a standard best practice on J2EE projects. I have been asked by the people working with me to modify this architecture to bring it more in line with the SAP way of doing things. I am open-minded and willing to learn and accept new ways of thinking and doing things. However, I fail to understand the usefulness of merging structure and behaviour by resorting to CommandBeans:
- It violates the MVC paradigm by having one object (the CommandBean) serve as both model AND controller as far as the Web Dynpro application is concerned. The CommandBean is obviously a model - since it is literally imported as such into the Web Dynpro application. It is ALSO a controller from the Web Dynpro's application perspective, since all calls to the back-end go thru the CommandBean via one or more of its execute_xxx methods. In contrast, the use of a business delegate by the Web Dynpro application clearly separates the model (the CommandBean... or rather, a more suitably named ModelBean) from the controller (BusinessDelegate).
- Doesn't carry its own weight. In other words, I haven't yet been provided with any valid justification for going thru the extra effort of coding the CommandBean's execute methods. It's been proposed to me that it somehow serves as an abstraction layer between the Web Dynpro application and the business logic. I would argue that it is the BusinessDelegate's role to abstract away the back-end logic from clients. If one does have a BusinessDelegate available, I would argue there's no need to code execute methods in a separate CommandBean. To prove my point, I would simply point out that all of the CommandBean examples that I have seen so far, either in How-To documents, or in production code, all follow the same pattern....
CommandBean.execute_doSomething() calls BusinessDelegate.doSomething()
Not a heck of an "abstraction" layer... I would in fact argue that it is worse than useless. If some major change occurs in the business logic that requires changing the doSomething() operation, we expect of course to modify the BusinessDelegate. The Web Dynpro client will also presumably need to be modified - that's to be expected, and unavoidable. But then, we'll also need to go about and change the CommandBean's execute_doSomething() method - again, extra work for no apparent benefit. Adding and removing business methods has the same implication. All this for an layer that simply adds the prefix execute_ in front of all business method calls... Is this "abstraction layer" worth the cost of creating and maintaining it ??
- Unnecessarily complicates error handling. I have been told that for technical reasons, it is recommended that all exceptions thrown by the CommandBean be of type WDException or WDRuntimException. But what if the client application needs to react differently to different failure scenarios ? When I create a business object, I might wish to provide the user with an error messages if connection is lost to the backend, and with a different error message if an object already exists in the database with the same attributes. In order to do that, I will have to catch the WDException, extract the cause, and continue processing from there... possible, yes, but clearly less standard and more labor intensive than the classical try/catch mechanism.
To say nothing about the fact that SAP's own API documentation clearly states that applications using Web Dynpro can reference and catch WDExceptions, but THEY MUST NOT THROW OR EXTEND IT !
- Produces unnecessary DCs. Page 6 of the aforementioned document presents an architectural view of a Web Dynpro project that uses a CommandBean. Why an extra DC for the CommandBean ?? I created my ModelBean class right inside the Web Dynpro project (in the Package view). That, to me, is where this class should reside, because it is created for no other reason that to be used by this particular Web Dynpro application. What is the benefit of placing it in its own independant DC ?
- Not a typical application of the Command pattern. The well-documented command pattern (Design Patterns - Gang of Four) has been devised mainly to enable encapsulation of request as objects, thereby making it possible to:
- specify, queue and execute requests at different times
- decouple execution of a command from its invoker
- support undo operations
- support logging changes so that they can be reapplied in case of system crash making it possible to assemble commands into composite commands (macros), thereby structuring a system around high-level operations built on primitive operations.
None of this applies to the way the SAP CommandBeans are being used. Not that much of an issue to people new to J2EE and/or OO development... but quite confusing for those already familiar with the classic Command pattern.
At this point, I fail to understand the advantage of merging structure (model) and behaviour (execute methods) through the use of a unique CommandBean object. Am I missing something ?

Thanks for your reply and your suggestion. I have posted in the Web Dynpro Java forum... and suggest those wishing to participate in this thread to refer to the Web Dynpro Java forum.
As for your answer, I'm afraid it doesn't satisfy me.
Reuse is hardly an issue, since the CommandBean is specifically tailor-made for the Web Dynpro application that needs to use it. I could hardly imagine building another application that would just happen to have the exact same needs as far as data structure and processing is concerned...
As for the right Eclipse environment... the CommandBean is not an EJB artifact - it is an EJB client. The aforementioned tutorial in fact suggests creating it in the Java perspective.
But thanks anyway for your time and suggestion

Using EJB in XI

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