Best Practices for EJB--memory leak avoidance

I an researching a memory leak. From what I can tell, we do not want to put any instance variables at the class level. This would incur a memory leak when the ejb containers creates the ejb.
I am wondering if there are any more 'best practices' with EJBs that prevent memory leaks. A good site would help me too
Russ

Thank for your reply.
You are right. I was referring to stateless session
beans.
What I was thinking was the following:
1. Making parameters final unless the parameter
r state is changed inside a method.Won't help with memory leaks. There are benefits for an object being immutable, but I don't think that it eliminates the possibility of the object being leaked.
2. All instance variables in stateless session beans
s should be set to null upon ejbPassivate and
ejbRemove operations. The variables should be
populated on ejbCreate and ejbActivate.Optimizing compilers don't need the hint of setting the reference to null. I don't think that helps, but I'm not 100% certain.
3. Before throwing an exception at the session bean
level, clear up all the instance variables by setting
them to null.Shouldn't scope make it clear to the GC that the objects aren't needed? If they're all primitives, how does this help memory leaks?
I am using a profiler to identify the objects still
being held onto once GC, but I was hoping others with
more experience than I would share some of their tips
on how they avoid memory leaks.I don't know where you're getting these tips, but I don't think they're helpful.
Collections and Singletons would be the places where I'd look. If you add a reference to an object that holds onto it in a collection and never lets go, the GC won't reclaim it.
Singletons aren't cleaned up, because their instance is static. Anything the Singleton refers to won't be cleaned up unless the Singleton relinquishes the reference.
Look for things like that. I think they matter more.
%

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Hi Siva,
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Regards,
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----- any comments or opinions are welcome!!! ------

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I am developing an ADF application where the users do not want to use the mouse.
So I would like to know if there are a best practice for this?
I am already using the accessKey functionality and subforms defaultCommand
But I have had problems setting focus to objects on a page like tables. I would like a button to return the focus to the table after it has made the command like delete.
I have implemented a solution where I have found inspiration several threads and other webpages (see below).
Is this solution okay?
Are there any problems with it?
I would also like to know if there are better pathways to go like
out of the box solutions,
http://www.oracle.com/technetwork/developer-tools/adf/learnmore/79-global-template-button-strategy-360139.pdf (are there an example implementation?), or
http://one-size-doesnt-fit-all.blogspot.dk/2010/11/adf-ui-shell-supporting-global-hotkeys.html
in advance thanks
Inspiration webpages
https://blogs.oracle.com/jdevotnharvest/entry/how_to_programmatically_set_focus
http://technology.amis.nl/2008/01/04/adf-11g-rich-faces-focus-on-field-after-button-press-or-ppr-including-javascript-in-ppr-response-and-clientlisteners-client-side-programming-in-adf-faces-rich-client-components-part-2/
how to Commit table by writting Java code in Managed Bean?
Table does not refresh and getting error as UIComponent is Null
A short description of the solution:
(jdeveloper version 11.1.1.2.0)
--- Example where I use onSetFocus in jsff page
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partialSubmit="true" accessKey="f"
shortDesc="Alt+Shift+F"
actionListener="#{managedBean_clientUtils.onSetFocus}">
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<af:commandButton text="#{hrsusuiBundle.DELETE}" id="cb4"
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shortDesc="Alt+Shift+X"
partialSubmit="true"
actionListener="#{managedBean_clientUtils.doTableActionAndSetFocus}">
<af:clientAttribute name="focusField" value="t1"/>
<af:clientAttribute name="actionField" value="Delete"/>
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<af:commandButton text="#{hrsusuiBundle.COMMIT}" id="cb5"
accessKey="s" shortDesc="Alt+Shift+S"
partialSubmit="true"
actionListener="#{managedBean_clientUtils.doTableActionAndSetFocus}">
<af:clientAttribute name="focusField" value="t1"/>
<af:clientAttribute name="actionField" value="Commit"/>
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accessKey="z" shortDesc="Alt+Shift+Z"
partialSubmit="true"
actionListener="#{managedBean_clientUtils.doTableActionAndSetFocus}"
immediate="true">
<af:resetActionListener/>
<af:clientAttribute name="focusField" value="t1"/>
<af:clientAttribute name="actionField" value="Rollback"/>
</af:commandButton>
--- This is the java class I use
--- It is published in adfc-config.xml as a request scope managedbean
public class ClientUtils {
public ClientUtils() {
public void doTableActionAndSetFocus(ActionEvent event) {
RichCommandButton rcb = (RichCommandButton)event.getSource();
String focusOn = (String)rcb.getAttributes().get("focusField");
String actionToDo = (String)rcb.getAttributes().get("actionField");
UIComponent component = null;
String clientId = null;
component = JSFUtils.findComponentInRoot(focusOn);
clientId = component.getClientId(JSFUtils.getFacesContext());
if ( "Delete".equals(actionToDo) || "Commit".equals(actionToDo) || "Rollback".equals(actionToDo) ){
BindingContainer bindings = BindingContext.getCurrent().getCurrentBindingsEntry();
OperationBinding operationBinding = bindings.getOperationBinding(actionToDo);
Object result = operationBinding.execute();
AdfFacesContext.getCurrentInstance().addPartialTarget(component);
if (clientId != null) {
makeSetFocusJavaScript(clientId);
public static String onSetFocus(ActionEvent event) {
RichCommandButton rcb = (RichCommandButton)event.getSource();
String focusOn = (String)rcb.getAttributes().get("focusField");
String clientId = null;
if (focusOn.contains(":")) {
clientId = focusOn;
} else {
clientId = findComponentsClientIdInRoot(focusOn);
if (clientId != null) {
makeSetFocusJavaScript(clientId);
return null;
private static void writeJavaScriptToClient(String script) {
FacesContext fctx = FacesContext.getCurrentInstance();
ExtendedRenderKitService erks = null;
erks = Service.getRenderKitService(fctx, ExtendedRenderKitService.class);
erks.addScript(fctx, script);
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if (clientId != null) {
StringBuilder script = new StringBuilder();
//use client id to ensure component is found if located in
//naming container
script.append("var textInput = ");
script.append("AdfPage.PAGE.findComponentByAbsoluteId");
script.append ("('"+clientId+"');");
script.append("if(textInput != null){");
script.append("textInput.focus();");
script.append("}");
writeJavaScriptToClient(script.toString());
public static String findComponentsClientIdInRoot(String id) {
UIComponent component = null;
String clientId = null;
component = JSFUtils.findComponentInRoot(id);
clientId = component.getClientId(JSFUtils.getFacesContext());
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}

Hi,
I am developing an ADF application where the users do not want to use the mouse. So I would like to know if there are a best practice for this?
Well HTML (and this is the user interface you see) follows a tab index navigation that you follow with "tab" and "shift+tab". Anything else is a short cut for which you use mnemonics (as you already do) or shortcuts (explained in http://one-size-doesnt-fit-all.blogspot.dk/2010/11/adf-ui-shell-supporting-global-hotkeys.html). There is a distinction to make between non-web environments (which I think you and your users have abackground in) and client desktop environments. Browsers block some keyboard functionality for their own purpose. So you may have to find a list of keys first that work across browsers. Unlike desktop clients, which allow you to "press a button" without the button to take focus, this cannot be done on the web. So you need to be clever here, avoiding buttons at all.
The following paper is about JavaScript in ADF and explains the basics for what Chris Muir explains in : http://one-size-doesnt-fit-all.blogspot.dk/2010/11/adf-ui-shell-supporting-global-hotkeys.html
http://www.oracle.com/technetwork/developer-tools/jdev/1-2011-javascript-302460.pdf
It has the outline for how to register short cut keys that perform a specific action (e.g. register ctrl+d to delete the current row you are on, or press F11 to execute a query (similar to Oracle Forms frmres files)). However, be aware that this includes some code you have to write (actually quite some code to be honest).
http://www.oracle.com/technetwork/developer-tools/adf/learnmore/79-global-template-button-strategy-360139.pdf (are there an example implementation?), or
http://one-size-doesnt-fit-all.blogspot.dk/2010/11/adf-ui-shell-supporting-global-hotkeys.html
Actually these are implementations as they come with example code for you to use and customize, do they? So what is this question asking for more ? Also note that global buttons don't quite have anything in common with the question you asked. I assume you want to see it as an implementation of the Forms toolbar that operates on the form or table the focus is in. This however does not work for the web as there is nothing that keeps track of which component has a focus and to what iterator (data block) it belongs. This would involve even more coding (though possibly doable)
Frank

What are best practice for packaging and deploying j2EE apps to iAS?

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Recently however we have had a number of LDAP issues, particularly when registering and unregistering applications (registering ear files sometimes fails 1st time but may work 2nd time). Also We've noticed very occasionally that old versions of classes sometimes find their way onto our machines.
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3) Deploying ear files can take 5 to 10 mins, is this normal?
4) In a clustered scenario where HTTPSession is shared what are the consequences of doing deployments to data stored in session?
thanks in asvance for your replies
Owen

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2) In general it is better to undeploy then redeploy. However, if you know that you're not changing GUIDs, recreating an existing application with new GUIDs, or removing registered components, you may avoid the undeploy phase.
If you shut down the KJS processes during deployment you can eliminate some addition workload on the LDAP server which really gets pounded during deployment. This is because the KJS processes detect changes and do registry loads to repopulate their caches. This can happen many times during a deployment and does not provide any benefit.
3) Deploying can be a lengthy process. There have been improvements in that performance from service pack to service pack but unfortunately you wont see dramatic drops in deployment times.
One thing you can do to reduce deployment times is to understand the type of deployment. If you have not manipulated your deployment descriptors in any way, then there is no need to deploy. Simply drop your newer bits in to the run time space of the application server. In later service packs this means exploding the package (ear,war, or jar) in to the appropriate subdirectory of the APPS directory.
4) If you've changed the classes of objects that have been placed in HTTPSession, you may find that you can no longer utilize those objects. For that reason, it is suggested that objects placed in session be kept as simple as possible in order to minimize this effect. In general however, is not a good idea to change a web application during the life span of a session.

Best practice for remote topic subscription with HA

I'd like to create an orchestrator EJB, in cluster A, that must persist some data to a database of record and then publish a business event to a topic. I have two durable subscribers, MDBs on clusters B & C, that need to receive the events and perform some persistence on their side.
          I'd like HA so that a failure in any managed server would not interrupt the system. I can live with at least once delivery, but at the same time I'd like to minimize the amount of redundant message processing.
          The documentation gets a little convoluted when dealing with clustering. What is the best practice for accomplishing this task? Has anyone successfully implemented a similar solution?
          I'm using Weblogic 8.1 SP5, but I wouldn't mind hearing solutions for later versions as well.

A managed server failure makes that server's JMS servers unavailable, which, in turn, makes the JMS server's messages unavailable until the either (A) the JMS server is migrated or (B) the managed server is restarted.
          For more discussion, see my post today on topic "distributed destinations failover - can't access messages from other node". Also, you might be interested in the circa 8.1 migration white-paper on dev2dev: http://dev2dev.bea.com/pub/a/2004/05/ClusteredJMS.html
          Tom

Best Practices for EJB--memory leak avoidance

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