Stateless ejb staying live after a garbage collector
Hi,
I use an aplication based in struts, in the actions i call session that call cmps, both ejb are stateless.
Every thing works fine until i make some stress test, when i find that the server (Websphere) stay out of memory. After this i found that my sessions and cmps are staying live after the garbage collector run and i don't know why because the thread already finish and the ejb are stateless.
Anyone already have this problem, how can i clear the memory of this objects?
Thanks in advanced
Ricardo
Adjust the size of your EJB pool. Just because your application is no longer using the objects doesn't mean that the container won't hang on to them for re-use (object creation is an "expensive" operation).
Similar Messages
-
Can someone explain how garbage collector works in this program ?
class Chair {
static boolean gcrun = false;
static boolean f = false;
static int created = 0;
static int finalized = 0;
int i;
Chair() {
i = ++created;
if(created == 47)
System.out.println("Created 47");
public void finalize() {
if(!gcrun) {
// The first time finalize() is called:
gcrun = true;
System.out.println(
"Beginning to finalize after " +
created + " Chairs have been created");
if(i == 47) {
System.out.println(
"Finalizing Chair #47, " +
"Setting flag to stop Chair creation");
f = true;
finalized++;
if(finalized >= created)
System.out.println(
"All " + finalized + " finalized");
public class Garbage {
public static void main(String[] args) {
// As long as the flag hasn't been set,
// make Chairs and Strings:
while(!Chair.f) {
new Chair();
new String("To take up space");
System.out.println(
"After all Chairs have been created:\n" +
"total created = " + Chair.created +
", total finalized = " + Chair.finalized);
// Optional arguments force garbage
// collection & finalization:
if(args.length > 0) {
if(args[0].equals("gc") ||
args[0].equals("all")) {
System.out.println("gc():");
System.gc();
if(args[0].equals("finalize") ||
args[0].equals("all")) {
System.out.println("runFinalization():");
System.runFinalization();
System.out.println("bye!");
} ///:~
This code is From Bruce Eckel's "thinking in Java"
Here is what I understand and what I don't
At a certain point during the execution of the while loop (in the method main), the garbage collector kicks in and will call the method finalize() -
I am at a loss as to what happens afterwards -
Do the chairs continue to get created (which means the variable i keeps incrementing) and the finalize method keep getting called (which means finalized keeps incrementing) till the system realizes it is really low on memory and starts reclaiming memory ie i now starts decrementing ?
What I would like to know is the exact flow or execution of the code after the garbage collector starts kicking in ie. what happens to the variables "i" (does it increment and then decrement), "created" (does it keep incrementing ), "finalized" (does it keep incrementing) and when is the if i==47{ } statement within finalize() get executed.
There is no part of the code where i is being decremented (so I am guessing that it is the garbage collector reclaiming object memory that must be decrementing it).
I am really confused -unfortunately there's very little in the book that really explains the flow of execution after the garbage collector kicks in and finalize() is called.
Any help would be greatly appreciatedNice example, but Bruce chose some suboptimal names, I think.
"i" can be thought of as the "ID" of a given Chair (note that it is not static). It is neither incremented nor decremented - it's just assigned from "created". This lets us identify specific chairs (like, say, "Chair #47").
"created" is a running total of the number of times the Chair constructor has been called.
"finalized" is a running total of the number of Chairs that have been finalized.
The process starts creating Chairs as fast as it can. Eventually, memory gets low, and gc() starts collecting Chairs. While that's happening, chairs are still being created in the main Thread. So "created" and "finalized" may both be incrementing at the same time.
When gc() picks Chair#47, the finalizer code sets a flag that causes new Chairs to stop being created. This causes the program to fall out of the while() loop, and the program spits out its data and exits.
On my machine, the program created 29,542 chairs before exiting.
Remember - often, gc() runs only when/if the JVM decides it's running low on memory. Specifics depend on the JVM and the startup options you use - some JVMs are very, very clever about doing incremental garbage-collection these days.
Does that make more sense?
Grant
(PS - it's very, very good that you posted a working code sample. But learn about the \[code\] and \[code\] tags, please - makes your sample WAY easier to read...) -
Automatic Garbage collector after JVM almost hit max value on weblogic ?
Hi All,
I have application on weblogic 10MP2. I use 4G JVM. My application getting slow when the usage of JVM hit arround 70-80% of max heap size. Unfortunatelly, the garbage collector didn't run when it hit that high. So to keep my application in good state, I need to MANUALLY hit the Perform GC to keep the JVM below 70%.
Is there any settings to tell the JVM to perform GC when the free space of the JVM hit 30%?
What will the weblogic do if one of the server in warning state? There is a settings in the weblogic to specify when it hit some percentage of free space, it will bring the server to warning state. Will it do the Garbage Collector?
Need your help on this. I am tired of hitting the Perform GC button.
Really appeciate your help.
Thanks,
EricI am replying to my own post because I found a tool that
helped me solve in two hours what I had been stumped on
for the past few days.
The Heap Analysis Tool.
I had a major memory leak problem. I couldn't locate
the source until I downloaded and used this tool(for free).
This tool keeps track of memory used by objects,
each objects references, objects references by each
object, and all objects instances. All of this information
can be obtained in html format for efficient traversing
of object chains. I would highly recommend looking
this tool over if you intend on doing memory intensive
programming.
In case your curious where my error was I had two problems
which are now fixed. One. I had a couple of BufferedImages
that were leaking 30MB RAM. Two. I didn't know that using
ObjectStream's to read/write objects stored references
to the objects being written(preventing garbage collection).
Deffinately worth running the Heap Analysis Tool before
pointing a finger at System.gc(). -
Problem: The garbage collector on my server runs aprox every 1 min for
about 8 secs swamping the CPUs.
I started a not so big version of my "big server" using the following:
JDK 1.4
Windows NT 4.0
Compaq Proliant with 4 CPUs @ 800Mhz
4GB SDRAM
I am starting with the following parametrs:
-mx1536m -verbose:gc -XX:-DisableExplicitGC -Xrs
On start up, my server creates a lot of objects that will live forever. Over
time any time period only a few objects (in comparison) are created that
will die young. I assume that I want a large older generation and a smaller
young generation. I need enoug room in my older generation for my older
objects plus room for the minor collections since they use copy collection.
The verbose gc trace shows the collector running ~every min. Here is a snip
of the log:
17:35:57 | [Full GC 245559K->245496K(441840K), 8.2943686 secs]
17:36:35 | [Full GC 245577K->245507K(441840K), 8.2816641 secs]
17:37:13 | [Full GC 245588K->245526K(441840K), 8.3754267 secs]
17:37:52 | [Full GC 245617K->245554K(441840K), 8.2831863 secs]
17:38:30 | [Full GC 245635K->245573K(441840K), 8.2977681 secs]
I let the server run and there were hundres of these with never a minor gc.
My analysis (Are my assumtions correct?)
1. I do not see minor collections happening so I assume these full
collections are not caused by collection of the young generations.
2. Since during my test run I know that no one is hitting my server, there
should not be and are not and significant memory changes that would require
a minor collection (which is why I don't see them).
3. I am using Visobroker which, like RMI, may be making explicit gc calls.
To prevent this I tried calling -XX:+DisableExplicitGC yet the GC seems to
wants to run every minuite.
Is -XX:+DisableExplicitGC supported on JDK1.4 Win32?
Could something else be causing these Full GCs?
-ChrisI have one other suggestion, but it is a long shot. The total size of your heap is around 440M and the total in use is very close to 60% of that value.
Since the JVM by default tries will consider increasing the heap size (up to -Xmx) when the free space falls below 40% AFTER GC, perhaps it is GC-ing periodically because of that. This sounds stupid since it should adjust heap size because of GC, but it is worth a try.
You might consider this...
java -Xms440m -Xmx1536m -Xminf0.1 -Xmaxf0.9 ...
This will mean that the heap will only expand when you have less than 10% free and will contract only when you have more than 90% free, but only to value of -Xms.
You also might consider -Xincgc as well, which should eliminate the 8-second pauses in favor of a more distributed gc load. Since you are alrready getting hit by >10% GC overhead, this may give you overall greater throughput as well, but I wouldn't bet on it.
Are you using the -server JVM? If not, I'd switch to that as well.
Chuck -
Stateless EJB 3.0 to webservice
Hello,
I'm using EJB 3.0 deployed on weblogic server 10. I can deploy Stateless EJB without any problem.
If I add a @WebService tag above my stateless bean, my deployment fails with the following error:
Exception activating module: EJBModule(EfanetTA_EJB.jar) Unable to deploy EJB: ProfilesFacade from EfanetTA_EJB.jar: Unable to deploy EJB: EfanetTA_EJB.jar from EfanetTA_EJB.jar: [HTTP:101216]Servlet: "WSEE_SERVLET" failed to preload on startup in Web application: "/BusinessManager". class: lu.efa.ejb.jaxws.FindProfilesById could not be found at com.sun.xml.ws.model.RuntimeModeler.getClass(RuntimeModeler.java:272) at com.sun.xml.ws.model.RuntimeModeler.processDocWrappedMethod(RuntimeModeler.java:566) at com.sun.xml.ws.model.RuntimeModeler.processMethod(RuntimeModeler.java:513) at com.sun.xml.ws.model.RuntimeModeler.processClass(RuntimeModeler.java:358) at com.sun.xml.ws.model.RuntimeModeler.buildRuntimeModel(RuntimeModeler.java:245) at com.sun.xml.ws.server.EndpointFactory.createSEIModel(EndpointFactory.java:229) at com.sun.xml.ws.server.EndpointFactory.createEndpoint(EndpointFactory.java:161) at com.sun.xml.ws.api.server.WSEndpoint.create(WSEndpoint.java:291) at com.sun.xml.ws.api.server.WSEndpoint.create(WSEndpoint.java:315) at weblogic.wsee.jaxws.JAXWSServlet.registerEndpoint(JAXWSServlet.java:125) at weblogic.wsee.jaxws.JAXWSServlet.init(JAXWSServlet.java:64) at javax.servlet.GenericServlet.init(GenericServlet.java:241) at weblogic.servlet.internal.StubSecurityHelper$ServletInitAction.run(StubSecurityHelper.java:282) at weblogic.security.acl.internal.AuthenticatedSubject.doAs(AuthenticatedSubject.java:321) at weblogic.security.service.SecurityManager.runAs(Unknown Source) at weblogic.servlet.internal.StubSecurityHelper.createServlet(StubSecurityHelper.java:63) at weblogic.servlet.internal.StubLifecycleHelper.createOneInstance(StubLifecycleHelper.java:58) at weblogic.servlet.internal.StubLifecycleHelper.<init>(StubLifecycleHelper.java:48) at weblogic.servlet.internal.ServletStubImpl.prepareServlet(ServletStubImpl.java:504) at weblogic.servlet.internal.WebAppServletContext.preloadServlet(WebAppServletContext.java:1830) at weblogic.servlet.internal.WebAppServletContext.loadServletsOnStartup(WebAppServletContext.java:1807) at weblogic.servlet.internal.WebAppServletContext.preloadResources(WebAppServletContext.java:1727) at weblogic.servlet.internal.WebAppServletContext.start(WebAppServletContext.java:2890) at weblogic.servlet.internal.WebAppModule.startContexts(WebAppModule.java:948) at weblogic.servlet.internal.WebAppModule.start(WebAppModule.java:353) at weblogic.wsee.deploy.WseeWebappModule.activate(WseeWebappModule.java:139) at weblogic.wsee.deploy.WSEEEjbModule.activate(WSEEEjbModule.java:371) at weblogic.wsee.deploy.WsEJBDeployListener.activate(WsEJBDeployListener.java:52) at weblogic.ejb.container.deployer.EJBDeployer.activate(EJBDeployer.java:1414) at weblogic.ejb.container.deployer.EJBModule.activate(EJBModule.java:423) at weblogic.application.internal.flow.ModuleListenerInvoker.activate(ModuleListenerInvoker.java:107) at weblogic.application.internal.flow.DeploymentCallbackFlow$2.next(DeploymentCallbackFlow.java:381) at weblogic.application.utils.StateMachineDriver.nextState(StateMachineDriver.java:26) at weblogic.application.internal.flow.DeploymentCallbackFlow.activate(DeploymentCallbackFlow.java:71) at weblogic.application.internal.flow.DeploymentCallbackFlow.activate(DeploymentCallbackFlow.java:63) at weblogic.application.internal.BaseDeployment$2.next(BaseDeployment.java:635) at weblogic.application.utils.StateMachineDriver.nextState(StateMachineDriver.java:26) at weblogic.application.internal.BaseDeployment.activate(BaseDeployment.java:212) at weblogic.application.internal.DeploymentStateChecker.activate(DeploymentStateChecker.java:154) at weblogic.deploy.internal.targetserver.AppContainerInvoker.activate(AppContainerInvoker.java:80) at weblogic.deploy.internal.targetserver.operations.AbstractOperation.activate(AbstractOperation.java:566) at weblogic.deploy.internal.targetserver.operations.ActivateOperation.activateDeployment(ActivateOperation.java:136) at weblogic.deploy.internal.targetserver.operations.ActivateOperation.doCommit(ActivateOperation.java:104) at weblogic.deploy.internal.targetserver.operations.StartOperation.doCommit(StartOperation.java:139) at weblogic.deploy.internal.targetserver.operations.AbstractOperation.commit(AbstractOperation.java:320) at weblogic.deploy.internal.targetserver.DeploymentManager.handleDeploymentCommit(DeploymentManager.java:816) at weblogic.deploy.internal.targetserver.DeploymentManager.activateDeploymentList(DeploymentManager.java:1223) at weblogic.deploy.internal.targetserver.DeploymentManager.handleCommit(DeploymentManager.java:434) at weblogic.deploy.internal.targetserver.DeploymentServiceDispatcher.commit(DeploymentServiceDispatcher.java:161) at weblogic.deploy.service.internal.targetserver.DeploymentReceiverCallbackDeliverer.doCommitCallback(DeploymentReceiverCallbackDeliverer.java:181) at weblogic.deploy.service.internal.targetserver.DeploymentReceiverCallbackDeliverer.access$100(DeploymentReceiverCallbackDeliverer.java:12) at weblogic.deploy.service.internal.targetserver.DeploymentReceiverCallbackDeliverer$2.run(DeploymentReceiverCallbackDeliverer.java:67) at weblogic.work.SelfTuningWorkManagerImpl$WorkAdapterImpl.run(SelfTuningWorkManagerImpl.java:464) at weblogic.work.ExecuteThread.execute(ExecuteThread.java:200) at weblogic.work.ExecuteThread.run(ExecuteThread.java:172)
Thank's for your help.
ThomasI am facing a new problem, i tried to create the folowing build script:
<project default="build_artefacts">
<taskdef name="apt" classname="com.sun.tools.ws.ant.Apt">
<classpath refid="jaxws.classpath" />
</taskdef>
<target name="compile-server">
<echo message="Compiling server classes" />
<javac destdir="target/classes" includes="**/com/**">
<src path="com/b2winc/controlpanel/business/facade/customer" />
<classpath refid="project.classpath" />
</javac>
</target>
<target name="apt" depends="compile-server">
<apt destdir="${build}" sourcedestdir="${generated}" sourcepath="${src}">
<classpath refid="jaxws.classpath" />
<source dir="${src}">
<include name="**com/b2winc/controlpanel/business/*.java" />
</source>
</apt>
</target>
<target name="build_artefacts" depends="apt">
<echo message="${src}"></echo>
<taskdef name="antwsgen" classname="com.sun.tools.ws.ant.WsGen"
classpath="${src}jaxws/lib/jaxws-tools.jar" />
<antwsgen
sei="CustomerFacade" verbose="true"
destdir="target/classes" sourcedestdir="target/temp" >
<classpath path="jaxws.classpath"/>
</antwsgen>
</target>
<path id="jaxws.classpath">
<pathelement path="jaxws-ri-121/lib/jaxws-tools.jar" />
<pathelement path="jaxws-ri-121/lib/jaxb-api.jar" />
<pathelement path="jaxws-ri-121/lib/jaxb-impl.jar" />
<pathelement path="jaxws-ri-121/lib/jaxws-api.jar" />
</path>
</project> I used this guideline: http://today.java.net/pub/a/today/2006/06/13/web-services-with-jax-ws-2.0.html
And i get the following error:
[apt] An exception has occurred in apt (1.5.0_11). Please file a bug at th
e Java Developer Connection (http://java.sun.com/webapps/bugreport) after check
ing the Bug Parade for duplicates. Include your program and the following diagno
stic in your report. Thank you.
[apt] java.lang.NoClassDefFoundError: com/sun/mirror/apt/AnnotationProcessorFactoryThe strange thing, that this class belongs to the tools.jar inside my JDK 5.
Thanks
Carlos -
HOWTO: Using a BC4J Application Module in an Stateless EJB Session Bean
HOWTO: Using a BC4J Application Module in an Stateless EJB Session Bean
by Steve Muench
Overview
BC4J provides automatic facilities for deploying any application module as a stateful EJB session bean. If you want to leverage the features of your BC4J application module from a stateless EJB session bean, it's not automatic but it is straightforward to implement. This howto article explains the details.
For our example, we will create a stateless EJB session bean that uses a container-managed transaction. To keep things simple, let's assume the session bean has a single public method on its remote interface named createDepartment() with the following signature:
public void createDepartment(int id, String name, String loc) throws AppException
AppException is an example of an application-specific exception that our method will throw if any problems arise during its execution.The goal of this article is to illustrate how to use the BC4J application module named com.example.hr.HRApp as part of the implementation of this createDepartment method on our stateless enterprise bean. Let's assume that the HRApp application module has a view object member named Departments, based on the com.example.hr.DeptView view object, based on the familiar DEPT table and related to the com.example.hr.Dept entity object so our view can be updateable.
Creating the Stateless Session Bean
We can start by using the JDeveloper Enterprise Bean wizard to create a new stateless session bean called StatelessSampleEJB implemented by:[list][*]com.example.StatelessSampleEJBBean (Bean class)[*]com.example.StatelessSampleEJBHome (Home interface)[*]com.example.StatelessSampleEJB (Remote interface)[list]
We then use the EJB Class Editor to add the createDepartment method to the remote interface of StatelessSampleEJB with the signature above. We edit the remote interface to make sure that it also reflects that the createDepartment method thows the AppException like this:
package com.example;
import javax.ejb.EJBObject;
import java.rmi.RemoteException;
public interface StatelessSampleEJB extends EJBObject {
void createDepartment(int id, String name, String loc)
throws RemoteException,AppException;
}Before we start adding BC4J into the picture for our implementation, our StatelessSampleEJBBean class looks like this:
package com.example;
import javax.ejb.SessionBean;
import javax.ejb.SessionContext;
public class StatelessSampleEJBBean implements SessionBean {
public void ejbCreate(){}
public void ejbActivate(){}
public void ejbPassivate(){}
public void ejbRemove(){}
public void setSessionContext(SessionContext ctx){
public void createDepartment(int id, String name, String loc)
throws AppException {
// TODO: Implement method here
}We can double-click on the ejb-jar.xml file in our project to see the XML deployment descriptor for the bean we just created:
<ejb-jar>
<enterprise-beans>
<session>
<description>Session Bean ( Stateless )</description>
<display-name>StatelessSampleEJB</display-name>
<ejb-name>StatelessSampleEJB</ejb-name>
<home>com.example.StatelessSampleEJBHome</home>
<remote>com.example.StatelessSampleEJB</remote>
<ejb-class>com.example.StatelessSampleEJBBean</ejb-class>
<session-type>Stateless</session-type>
<transaction-type>Container</transaction-type>
</session>
</enterprise-beans>
</ejb-jar>We need to add the extra <assembly-descriptor> section in this file to indicate that the createDepartment method will require a transaction. After this edit, the ejb-jar.xml file looks like this:
<ejb-jar>
<enterprise-beans>
<session>
<description>Session Bean ( Stateless )</description>
<display-name>StatelessSampleEJB</display-name>
<ejb-name>StatelessSampleEJB</ejb-name>
<home>com.example.StatelessSampleEJBHome</home>
<remote>com.example.StatelessSampleEJB</remote>
<ejb-class>com.example.StatelessSampleEJBBean</ejb-class>
<session-type>Stateless</session-type>
<transaction-type>Container</transaction-type>
</session>
</enterprise-beans>
<assembly-descriptor>
<container-transaction>
<method>
<ejb-name>StatelessSampleEJB</ejb-name>
<method-name>createDepartment</method-name>
<method-params>
<method-param>int</method-param>
<method-param>java.lang.String</method-param>
<method-param>java.lang.String</method-param>
</method-params>
</method>
<trans-attribute>Required</trans-attribute>
</container-transaction>
</assembly-descriptor>
</ejb-jar>
Aggregating a BC4J Application Module
With the EJB aspects of our bean setup, we can proceed to implementing the BC4J application module aggregation.
The first thing we do is add private variables to hold the EJB SessionContext and the instance of the aggregated BC4J ApplicationModule, like this:
// Place to hold onto the aggregated appmodule instance
transient private ApplicationModule _am = null;
// Remember the SessionContext that the EJB container provides us
private SessionContext _ctx = null;and we modify the default, empty implementation of the setSessionContext() method to remember the session context like this:
public void setSessionContext(SessionContext ctx){ _ctx = ctx; }We add additional constants that hold the names of the J2EE datasource that we want BC4J to use, as well as the fully-qualified name of the BC4J application module that we'll be aggregating:
// JNDI resource name for the J2EE datasource to use
private static final String DATASOURCE = "jdbc/OracleCoreDS";
// Fully-qualified BC4J application module name to aggregate
private static final String APPMODNAME = "com.example.hr.HRApp";We expand the now-empty ejbCreate() and ejbRemove() methods to create and destory the aggregated instance of the BC4J application module that we'll use for the lifetime of the stateless session bean. When we're done, ejbCreate() it looks like this:
public void ejbCreate() throws CreateException {
try {
// Setup a hashtable of environment parameters for JNDI initial context
Hashtable env = new Hashtable();
env.put(JboContext.INITIAL_CONTEXT_FACTORY,JboContext.JBO_CONTEXT_FACTORY);
// NOTE: we want to use the BC4J app module in local mode as a simple Java class!
env.put(JboContext.DEPLOY_PLATFORM, JboContext.PLATFORM_LOCAL);
env.put(PropertyConstants.INTERNAL_CONNECTION_PARAMS,DATASOURCE);
// Create an initial context, using this hashtable of environment params
InitialContext ic = new InitialContext(env);
// Lookup a home interface for the application module
ApplicationModuleHome home = (ApplicationModuleHome)ic.lookup(APPMODNAME);
// Using the home, create the instance of the appmodule we'll use
_am = home.create();
// Register the BC4J factory to handle EJB container-managed transactions
registerContainerManagedTransactionHandlerFactory();
catch(Exception ex) {
ex.printStackTrace();
throw new CreateException(ex.getMessage());
}and ejbRemove() looks like this:
public void ejbRemove() {
try {
// Cleanup any appmodule resources before getting shutdown
_am.remove();
catch(JboException ex) { /* Ignore */ }
}The helper method named reigsterContainerManagedTransactionHandlerFactory() looks like this:
private void registerContainerManagedTransactionHandlerFactory() {
SessionImpl session = (SessionImpl)_am.getSession();
session.setTransactionHandlerFactory(
new TransactionHandlerFactory() {
public TransactionHandler createTransactionHandler() {
return new ContainerManagedTxnHandlerImpl();
public JTATransactionHandler createJTATransactionHandler() {
return new ContainerManagedTxnHandlerImpl();
}The last detail is to use the BC4J appmodule to implement the createDepartment() method. It ends up looking like this:
public void createDepartment(int id, String name, String loc)
throws AppException {
try {
// Connect the AM to the datasource we want to use for the duration
// of this single method call.
_am.getTransaction().connectToDataSource(null,DATASOURCE,false);
// Use the "Departments" view object member of this AM
ViewObject departments = _am.findViewObject("Departments");
// Create a new row in this view object.
Row newDept = departments.createRow();
// Populate the attributes from the parameter arguments.
newDept.setAttribute("Deptno", new Number(id));
newDept.setAttribute("Dname", name);
newDept.setAttribute("Loc", loc);
// Add the new row to the view object's default rowset
departments.insertRow(newDept);
// Post all changes in the AM, but we don't commit them. The EJB
// container managed transaction handles the commit.
_am.getTransaction().postChanges();
catch(JboException ex) {
// To be good EJB Container-Managed Transaction "citizens" we have
// to mark the transaction as needing a rollback if there are problems
_ctx.setRollbackOnly();
throw new AppException("Error creating dept "+ id +"\n"+ex.getMessage());
finally {
try {
// Disconnect the AM from the datasource we're using
_am.getTransaction().disconnect();
catch(Exception ex) { /* Ignore */ }
Building a Test Client
With the EJB-Tier work done, we can build a sample client program to test this new stateless EJB Session Bean by selecting the bean in the Oracle9i JDeveloper IDE and choosing "Create Sample Java Client" from the right-mouse menu.
When the "Sample EJB Client Details" dialog appears, we take the defaults of connecting to embedded OC4J container. Clicking the (OK) button generates the following test class:
import java.util.Hashtable;
import javax.naming.Context;
import javax.naming.InitialContext;
import com.example.StatelessSampleEJB;
import com.example.StatelessSampleEJBHome;
public class SampleStatelessSampleEJBClient {
public static void main(String [] args) {
SampleStatelessSampleEJBClient sampleStatelessSampleEJBClient =
new SampleStatelessSampleEJBClient();
try {
Hashtable env = new Hashtable();
env.put(Context.INITIAL_CONTEXT_FACTORY,
"com.evermind.server.rmi.RMIInitialContextFactory");
env.put(Context.SECURITY_PRINCIPAL, "admin");
env.put(Context.SECURITY_CREDENTIALS, "welcome");
env.put(Context.PROVIDER_URL,
"ormi://localhost:23891/current-workspace-app");
Context ctx = new InitialContext(env);
StatelessSampleEJBHome statelessSampleEJBHome =
(StatelessSampleEJBHome)ctx.lookup("StatelessSampleEJB");
StatelessSampleEJB statelessSampleEJB;
// Use one of the create() methods below to create a new instance
// statelessSampleEJB = statelessSampleEJBHome.create();
// Call any of the Remote methods below to access the EJB
// statelessSampleEJB.createDepartment( int id, java.lang.String name, java.lang.String loc );
catch(Throwable ex) {
ex.printStackTrace();
}We uncomment the call to the create() method and add a few calls to the createDepartment() method so that the body of the test program now looks like this:
// Use one of the create() methods below to create a new instance
statelessSampleEJB = statelessSampleEJBHome.create();
// Call any of the Remote methods below to access the EJB
statelessSampleEJB.createDepartment( 13, "Test1","Loc1");
System.out.println("Created department 13");
statelessSampleEJB.createDepartment( 14, "Test2","Loc2");
System.out.println("Created department 14");
try {
// Try setting a department id that is too large!
statelessSampleEJB.createDepartment( 23456, "Test3","Loc3");
catch (AppException ax) {
System.err.println("AppException: "+ax.getMessage());
}Before we can successfully run our SampleStatelessSampleEJBClient we need to first run the EJB bean that the client will try to connect to. Since Oracle9i JDeveloper supports local running and debugging of the EJB-Tier without doing through a full J2EE deployment step, to accomplish this prerequisite step we just need to right-mouse on the StatelessSampleEJB node in the System Navigator and select "Run". This starts up the embedded OC4J instance and runs the EJB right out of the current out path.Finally, we can run the SampleStatelessSampleEJBClient, and see the output of the test program in the JDeveloper log window:
Created department 13
Created department 14
AppException: Error creating dept 23456
JBO-27010: Attribute set with value 23456 for Deptno in Dept has invalid precision/scale
Troubleshooting
One error that might arise while running the example is that the database connection information in your data-sources.xml for the jdbc/OracleCoreDS datasource does not correspond to the database you are trying to test against. If this happens, then double-check the file .\jdev\system\oc4j-config\data-sources.xml under the JDeveloper installation home directory to make sure that the url value provided is what you expect. For example, to work against a local Oracle database running on your current machine, listening on port 1521, with SID of ORCL, you would edit this file to have an entry like this for jdbc/OracleCoreDS :
<data-source
class="com.evermind.sql.DriverManagerDataSource"
name="OracleDS"
location="jdbc/OracleCoreDS"
xa-location="jdbc/xa/OracleXADS"
ejb-location="jdbc/OracleDS"
connection-driver="oracle.jdbc.driver.OracleDriver"
username="scott"
password="tiger"
url="jdbc:oracle:thin:@localhost:1521:ORCL"
inactivity-timeout="30"
/>This is the data-sources.xml file that gets used by the embedded OC4J instance running in JDeveloper.
Conclusion
Hopefully this article has illustrated that it is straightforward to utilize the full power of BC4J in local mode as part of your EJB Stateless Session Beans using container-managed transaction. This example illustrated a single createDepartment method in the enterprise bean, but by replicating the application module interaction code that we've illustrated in createDepartment, any number of methods in your stateless session bean can use the aggregated application module instance created in the ejbCreate() method.
Code Listing
The full code listing for the SampleStatelessEJB bean implementation class looks like this:
* StatelessSampleEJB
* Illustrates how to use an aggregated BC4J application module
* in local mode as part of the implementation of a stateless
* EJB session bean using container-managed transaction.
* HISTORY
* smuench/dmutreja 14-FEB-2002 Created
package com.example;
import oracle.jbo.*;
import oracle.jbo.server.*;
import javax.ejb.*;
import oracle.jbo.domain.Number;
import oracle.jbo.common.PropertyConstants;
import java.util.Hashtable;
import javax.naming.InitialContext;
import oracle.jbo.server.ejb.ContainerManagedTxnHandlerImpl;
public class StatelessSampleEJBBean implements SessionBean {
// JNDI resource name for the J2EE datasource to use
private static final String DATASOURCE = "jdbc/OracleCoreDS";
// Fully-qualified BC4J application module name to aggregate
private static final String APPMODNAME = "com.example.hr.HRApp";
// Place to hold onto the aggregated appmodule instance
transient private ApplicationModule _am = null;
// Remember the SessionContext that the EJB container provides us
private SessionContext _ctx = null;
public void ejbCreate() throws CreateException {
try {
// Setup a hashtable of environment parameters for JNDI initial context
Hashtable env = new Hashtable();
env.put(JboContext.INITIAL_CONTEXT_FACTORY,JboContext.JBO_CONTEXT_FACTORY);
env.put(JboContext.DEPLOY_PLATFORM, JboContext.PLATFORM_LOCAL);
env.put(PropertyConstants.INTERNAL_CONNECTION_PARAMS,DATASOURCE);
// Create an initial context, using this hashtable of environment params
InitialContext ic = new InitialContext(env);
// Lookup a home interface for the application module
ApplicationModuleHome home = (ApplicationModuleHome)ic.lookup(APPMODNAME);
// Using the home, create the instance of the appmodule we'll use
_am = home.create();
// Register the BC4J factory to handle EJB container-managed transactions
registerContainerManagedTransactionHandlerFactory();
catch(Exception ex) {
ex.printStackTrace();
throw new CreateException(ex.getMessage());
public void ejbActivate(){}
public void ejbPassivate(){}
public void ejbRemove(){}
public void setSessionContext(SessionContext ctx){ _ctx = ctx; }
public void createDepartment(int id, String name, String loc)
throws AppException {
try {
// Connect the AM to the datasource we want to use for the duration
// of this single method call.
_am.getTransaction().connectToDataSource(null,DATASOURCE,false);
// Use the "Departments" view object member of this AM
ViewObject departments = _am.findViewObject("Departments");
// Create a new row in this view object.
Row newDept = departments.createRow();
// Populate the attributes from the parameter arguments.
newDept.setAttribute("Deptno", new Number(id));
newDept.setAttribute("Dname", name);
newDept.setAttribute("Loc", loc);
// Add the new row to the view object's default rowset
departments.insertRow(newDept);
// Post all changes in the AM, but we don't commit them. The EJB
// container managed transaction handles the commit.
_am.getTransaction().postChanges();
catch(JboException ex) {
// To be good EJB Container-Managed Transaction "citizens" we have
// to mark the transaction as needing a rollback if there are problems
_ctx.setRollbackOnly();
throw new AppException("Error creating dept "+ id +\n"+ex.getMessage());
finally {
try {
// Disconnect the AM from the datasource we're using
_am.getTransaction().disconnect();
catch(Exception ex) { /* Ignore */ }
private void registerContainerManagedTransactionHandlerFactory() {
SessionImpl session = (SessionImpl)_am.getSession();
session.setTransactionHandlerFactory(
new TransactionHandlerFactory() {
public TransactionHandler createTransactionHandler() {
return new ContainerManagedTxnHandlerImpl();
public JTATransactionHandler createJTATransactionHandler() {
return new ContainerManagedTxnHandlerImpl();Hi Steve, It4s me again;
About the question I made, I tried with a single assembly-descriptor tag and a single container-transaction tag in the deployment descriptor of the session bean and these were the results.
java.lang.NullPointerException
void com.evermind.server.rmi.RMIConnection.EXCEPTION_ORIGINATES_FROM_THE_REMOTE_SERVER(java.lang.Throwable)
java.lang.Object com.evermind.server.rmi.RMIConnection.invokeMethod(com.evermind.server.rmi.RMIContext, long, long, java.lang.reflect.Method, java.lang.Object[])
java.lang.Object com.evermind.server.rmi.RemoteInvocationHandler.invoke(java.lang.Object, java.lang.reflect.Method, java.lang.Object[])
java.lang.Object com.evermind.server.rmi.RecoverableRemoteInvocationHandler.invoke(java.lang.Object, java.lang.reflect.Method, java.lang.Object[])
java.lang.Object com.evermind.server.ejb.StatelessSessionRemoteInvocationHandler.invoke(java.lang.Object, java.lang.reflect.Method, java.lang.Object[])
void __Proxy1.modificaEnvoltura(java.lang.Integer, java.lang.Integer, java.lang.Integer, java.lang.Integer, java.lang.Integer, java.lang.Integer, java.lang.String)
void SamplemdeController.envolturaControlEJBClient.main(java.lang.String[])
Then I tried with multiple assembly-descriptor tags each with a single container-transaction tag and the results were:
java.lang.NullPointerException
void com.evermind.server.rmi.RMIConnection.EXCEPTION_ORIGINATES_FROM_THE_REMOTE_SERVER(java.lang.Throwable)
java.lang.Object com.evermind.server.rmi.RMIConnection.invokeMethod(com.evermind.server.rmi.RMIContext, long, long, java.lang.reflect.Method, java.lang.Object[])
java.lang.Object com.evermind.server.rmi.RemoteInvocationHandler.invoke(java.lang.Object, java.lang.reflect.Method, java.lang.Object[])
java.lang.Object com.evermind.server.rmi.RecoverableRemoteInvocationHandler.invoke(java.lang.Object, java.lang.reflect.Method, java.lang.Object[])
java.lang.Object com.evermind.server.ejb.StatelessSessionRemoteInvocationHandler.invoke(java.lang.Object, java.lang.reflect.Method, java.lang.Object[])
void __Proxy1.modificaEnvoltura(java.lang.Integer, java.lang.Integer, java.lang.Integer, java.lang.Integer, java.lang.Integer, java.lang.Integer, java.lang.String)
void SamplemdeController.envolturaControlEJBClient.main(java.lang.String[])
Finally I tried with a single assembly-descriptor and multiple container tags and the results were:
java.lang.NullPointerException
void com.evermind.server.rmi.RMIConnection.EXCEPTION_ORIGINATES_FROM_THE_REMOTE_SERVER(java.lang.Throwable)
java.lang.Object com.evermind.server.rmi.RMIConnection.invokeMethod(com.evermind.server.rmi.RMIContext, long, long, java.lang.reflect.Method, java.lang.Object[])
java.lang.Object com.evermind.server.rmi.RemoteInvocationHandler.invoke(java.lang.Object, java.lang.reflect.Method, java.lang.Object[])
java.lang.Object com.evermind.server.rmi.RecoverableRemoteInvocationHandler.invoke(java.lang.Object, java.lang.reflect.Method, java.lang.Object[])
java.lang.Object com.evermind.server.ejb.StatelessSessionRemoteInvocationHandler.invoke(java.lang.Object, java.lang.reflect.Method, java.lang.Object[])
void __Proxy1.modificaEnvoltura(java.lang.Integer, java.lang.Integer, java.lang.Integer, java.lang.Integer, java.lang.Integer, java.lang.Integer, java.lang.String)
void SamplemdeController.envolturaControlEJBClient.main(java.lang.String[])
How can I make my Stateless Session bean work out? -
Possible Bug in Garbage Collector?
Hello all
I'm new to these forums but I searched for this problem and couldn't find exactly the same thing - apologies if I missed something.
I've written an image browser which displays thumbnails, and when you click on a thumbnail it loads the image in a new window. This new window is just a JFrame, with a single JLabel, with an ImageIcon in it, representing the picture. The path name of the picture is passed when this JFrame is created, and the picture is loaded within the JFrame. Therefore, when I close the JFrame, I expect the memory associated with the image to disappear.
This works. However, when I open a fairly large image (around 1500x1500 pixels), and then close the window, the garbage collector doesn't free the memory. After this, if i continue to open windows with smaller images, they too have the same problem. However, this doesn't happen with smaller images until I open a larger image.
I think this is a problem with the garbage collector, is this familiar to anyone? Can anyone help? Unfortunately I can't really paste code since this is a university assignment. But you can try it - just load a jframe with a large picture, close it, and as long as the program runs the memory will not be deallocated.
Any help would be massively appreciated.
ThanksSince you're not willing to post your code it's very hard to comment.
One question: Are you calling System.gc() after closing these frames? In fact you should probably call it 3 times to make sure the garbage collector takes you seriously. Try this and let us know if you're still showing the leak -
How to get the garbage collector to work?
Hi,
i have i program where i load an image scale it down and save the scaled version in an array. I do this for a whole directory of images.
After every image i set the temporary variable for the loaded image = null and call the function System.gc().
My problem is, that the garbage collector does�nt give the memory of the loaded image free and the used memory of my program grows with every loaded image.
/* Reads all images from a folder an stores them in an Array of images */
public static BufferedImage[] readScaledImagesFromFolder(String folder,
int maxSize) {
File dir = new File(folder); /* Open the Folder */
String[] children = dir.list(); /* Get the children of the folder */
if (children == null) {
// Either dir does not exist or is not a directory
System.out.println("No images in the folder!");
return null;
} else {
/* Init array for images */
BufferedImage[] images = new BufferedImage[children.length];
int i = 0;
int index = 0;
BufferedImage temp;
String filename, fileending;
for (i=0; i<children.length; i++) {
// Get filename of file or directory
filename = children;
/* Get the fileending of the file */
fileending = filename.toLowerCase().substring(filename.length()-4);
if(fileending.equals(".jpg") || fileending.equals(".bmp")
|| fileending.equals(".png") || fileending.equals(".gif"))
/* Read the image */
temp = util.ImageUtils.loadBufferedImage(folder+"/"+filename);
/* Scale the image down and save it in an array */
images[index] = Util.getScaledImage(temp,maxSize);
index++;
temp = null;
System.gc();
Mosaic.sourceImageNum = index;
System.out.println((index+1)+" resized pictures loaded from folder: "+folder);
return images;
How can i get the gargabe collector to work after every iteration?
I tried to let the Thread.sleep(10) after System.gc() but it does�nt help.
Thank you every much
JackNeilHm yes.. i now that System.gc() is only a
suggestion.
But i know what my program is doing and that it
does�nt need the temporary image anymore after i have
a scaled down version. And the temporay image will become unreachable as soon as reading the next one overwrites your temp variable. Setting the variable to null doesn't have much effect.
It would be smarter to load the new image over the
old temporary image and not to expand the heapsize to
maximum.Then look at the possibitly of loading the next image into the same bufferedimage. -
We have 2 CUCM clusters connected via an ICT. We are migrating users from CM8.6 to CM10.5. During the migration we are changing Users AD attributes so that they disappear from CM8. As this marks the user as Inactive in CM8 (and deletes after 24hrs) this prevents the User from logging into CM10 with EMCC.
Is there a way around this?
ie force the garbage collector to run immediately and delete the user
or remove certain fields in CUCM 8 against the user so that they can login using CUCM10 credentials?
Thanks
RichI think you can do something clever here. You can convert the inactive user on cucm 8 back to a standard cucm user and then delete them. This way you can control when to remove the user instea dof waiting for garbage collection. You become your own garbage man :)
You can conver the users back to standard CUCM users using sql query update...Ths is easy to do
run sql update enduser set status=1 ( this is the general command to make all users standard cucm users..you don't want to run this..)
Use this command to make specific users active. You need to use the users extension to filter which user gets converted to standard cucm user
run sql update enduser set status=1 where telephonenumber like ‘2%’
This command will update users with extension beginning with 2
or
run sql update enduser set status=1 where telephonenumber = '2001'
This will convert user with extension 2001 to a standard cucm user
To make sure you got all the users you can use the command
run sql select * from enduser where status=0
This should return zero entry. If you find any user there then use the update command on those users -
Stateless EJB is null using TimerService
Hi,
I created a stateless ejb using TimerService to run it in weblogic 10.3. After deploying it, I could not get the ejb instantiated properly. The code is as below.
Could anyone explain what is missing?
Thanks in advance.
//=================================================
public interface ReconTimer {
public void createTimer();
//================================================
import static javax.ejb.TransactionAttributeType.NOT_SUPPORTED;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import javax.annotation.Resource;
import javax.ejb.EJB;
import javax.ejb.Stateless;
import javax.ejb.Timeout;
import javax.ejb.Timer;
import javax.ejb.TimerService;
import javax.ejb.Local;
import javax.ejb.TransactionAttribute;
import javax.ejb.TransactionManagement;
import javax.ejb.TransactionManagementType;
@Stateless (name="ReconTimerBean")
@Local (ReconTimer.class)
@TransactionManagement(value=TransactionManagementType.BEAN )
@TransactionAttribute(value=NOT_SUPPORTED)
public class ReconTimerBean implements ReconTimer {
private static final Log log = LogFactory.getLog(ReconTimerBean.class);
@Resource
TimerService timerService;
public void createTimer() {
log.info("Crating timer");
log.info("timerService [" + timerService + "]");
Timer timer = timerService.createTimer(20000,
"Created new timer");
@Timeout
public void timeout(Timer timer) {
log.info("Timeout occurred !!!");
========================================
client code:
@EJB(beanName="ReconTimerBean")
ReconTimer timerBean
if (timerBean != null)
timerBean.createTimer();
else log.error ("Timer Bean is null !!!");
Error is always logged when the bean is deployed.
======================================
weblogic-ejb-jar.xml
<?xml version="1.0" encoding="UTF-8"?>
<weblogic-ejb-jar xmlns="http://www.bea.com/ns/weblogic/weblogic-ejb-jar"
xmlns:j2ee="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/ejb-jar_3_0.xsd http://www.bea.com/ns/weblogic/weblogic-ejb-jar http://www.bea.com/ns/weblogic/weblogic-ejb-jar/1.0/weblogic-ejb-jar.xsd">
<weblogic-enterprise-bean>
<ejb-name>ReconTimerBean</ejb-name>
<stateless-session-descriptor>
<pool>
<max-beans-in-free-pool>1</max-beans-in-free-pool>
<initial-beans-in-free-pool>1</initial-beans-in-free-pool>
</pool>
</stateless-session-descriptor>
<jndi-name>app-recon-bean</jndi-name>
</weblogic-enterprise-bean>
</weblogic-ejb-jar>Hi Ashley,
The Dependency injection has some limitations as well…Please referto the following link: (Web Component Classes That Support Annotations)
http://download.oracle.com/docs/cd/E13222_01/wls/docs100/webapp/annotateservlet.html
…Which says that DI is not possible from every web component.
Thanks
Jay SenSharma
http://jaysensharma.wordpress.com/ejbs_weblogic/#comment-165 (Dependency Injection Issues) -
In Java, there is one system call for garbage collector.
System.gc();
I want to know the significance of this system call for GC. Even after calling this method, garbage collector won't get started, still it will run on its own time.
If this is the thing then what's the significance of this method call?
Please let me know this.
Thanking you,
KetanAddendum
In a heavy data application, for instance, that stores records in memory for some purpose, then releases that memory and creates next set of records in memory, calling gc really help.
We have such application where in we tested its performance with and without calling gc. No wonder, we found better results by calling gc. -
Error "The current garbage collector has no nursery"
Has anybody any information on the error message "The current garbage collector has no nursery"? We received the following error message after starting the WLS in production mode:
<2006-jan-25 kl 17:57 CET> <Error> <Management> <BEA-140001> <An error occurred while getting attribute TotalNurserySize on MBean se-i-ld09:Location=se-i-ld09-c01-s01,Name=se-i-ld09-c01-s01,ServerRuntime=se-i-ld09-c01-s01,Type=JRockitRuntime. Method: public long weblogic.t3.srvr.JRockitRuntime.getTotalNurserySize(). Exception: com.bea.jvm.NotAvailableException: The current garbage collector has no nursery..
com.bea.jvm.NotAvailableException: The current garbage collector has no nursery.
at jrockit.management.jvm.GarbageCollectorImpl.getNurserySize()J(Unknown Source)
at weblogic.t3.srvr.JRockitRuntime.getTotalNurserySize()J(JRockitRuntime.java:112)
at jrockit.reflect.NativeMethodInvoker.invoke0(Ljava.lang.Object;ILjava.lang.Object;[Ljava.lang.Object&)Ljava.lang.Object;(Unknown Source)
at jrockit.reflect.NativeMethodInvoker.invoke(Ljava.lang.Object;[Ljava.lang.Object&)Ljava.lang.Object;(Optimized Method)
at jrockit.reflect.VirtualNativeMethodInvoker.invoke(Ljava.lang.Object;[Ljava.lang.Object&)Ljava.lang.Object;(Optimized Method)
at java.lang.reflect.Method.invoke(Ljava.lang.Object;[Ljava.lang.Object;I)Ljava.lang.Object;(Optimized Method)
at weblogic.management.internal.DynamicMBeanImpl.getAttribute(Ljava.lang.String&)Ljava.lang.Object;(DynamicMBeanImpl.java:574)
at com.sun.management.jmx.MBeanServerImpl.getAttribute(Ljava.lang.Object;Ljava.lang.String&)Ljava.lang.Object;(MBeanServerImpl.java:1183)
at com.sun.management.jmx.MBeanServerImpl.getAttribute(Ljavax.management.ObjectName;Ljava.lang.String&)Ljava.lang.Object;(MBeanServerImpl.java:1153)
at weblogic.management.internal.RemoteMBeanServerImpl.getAttribute(Ljavax.management.ObjectName;Ljava.lang.String&)Ljava.lang.Object;(RemoteMBeanServerImpl.java:287)
at weblogic.management.internal.RemoteMBeanServerImpl_WLSkel.invoke(ILweblogic.rmi.spi.InboundRequest;Lweblogic.rmi.spi.OutboundResponse;Ljava.lang.Object&)Lweblogic.rmi.spi.OutboundResponse;(Unknown Source)
at weblogic.rmi.internal.BasicServerRef.invoke(Lweblogic.rmi.extensions.server.RuntimeMethodDescriptor;Lweblogic.rmi.spi.InboundRequest;Lweblogic.rmi.spi.OutboundResponse&)V(BasicServerRef.java:477)
at weblogic.rmi.internal.BasicServerRef$1.run()Ljava.lang.Object;(BasicServerRef.java:420)
at weblogic.security.acl.internal.AuthenticatedSubject.doAs(Lweblogic.security.subject.AbstractSubject;Ljava.security.PrivilegedExceptionAction&)Ljava.lang.Object;(AuthenticatedSubject.java:363)
at weblogic.security.service.SecurityManager.runAs(Lweblogic.security.acl.internal.AuthenticatedSubject;Lweblogic.security.acl.internal.AuthenticatedSubject;Ljava.security.PrivilegedExceptionAction&)Ljava.lang.Object;(SecurityManager.java:144)
at weblogic.rmi.internal.BasicServerRef.handleRequest(Lweblogic.rmi.spi.InboundRequest&)V(BasicServerRef.java:415)
at weblogic.rmi.internal.BasicExecuteRequest.execute(Lweblogic.kernel.ExecuteThread&)V(BasicExecuteRequest.java:30)
at weblogic.kernel.ExecuteThread.execute(Lweblogic.kernel.ExecuteRequest&)V(ExecuteThread.java:219)
at weblogic.kernel.ExecuteThread.run()V(ExecuteThread.java:178)
at java.lang.Thread.startThreadFromVM(Ljava.lang.Thread&)V(Unknown Source)>
Thanks in advance for your help - it is much appreciated!
Cheers, JonasThis exception is thrown by the JRockit Management API when querying the nursery size of a GC that has no nursery (single-generational GC). The logical place to catch the error would be in the weblogic.t3.srvr.JRockitRuntime.getTotalNurserySize() method, which implies that it is a WLS issue.
Maybe it has been fixed in a later WLS 8.1 service pack?
If you run with a generational GC, i.e. "-Xgc:gencon" the error will go away, but that has larger implications on the behavior of your app so it should not be used as a workaround. -
Swing components and the garbage collector
How much care does one need to take with swing components, with reference to running out of stack space? I ask because I'm writing a system for an automotive parts company, and the company tends to not reboot the machines very often...
Anyway... if a JFrame is closed, is it and all its components marked for GCing? Do I need to call the dispose method, or is this part of the default close behaviour? Or is there something else entirely?
CheersIn class that calls for .setVisible(false) of one JFrame u MUST call
for dispose() method.
so
myFrame.setVisible(false)
myFrame.dispose()
myFrame = null // to help the garbage collector
If u have classes that becames from JFrame (or JDialog) u can
invoke in its constructors:
this.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE)
This makes uncecessary to call for dispose() method explicetly.
If u do not have this kind of classes u can invoke this method
after u have create your JFrame
JFrame myFrame = new JFrame();
myFrame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE)
The most important thing is REMOVE ALL LISETNERS that u have added, so, if u have classes that becames from JFrame u can ovverride
the dispose method to do that
eg
public void dispose()
super.dispose()
removeActionListener(.....)
and so on
If u do not have this kind of classes u must remove all listeners u have
added before u invoke the setVisible(false) method.
Regards -
Problem with garbage collector -
I'm experiencing a problem with the Java Garbage Collector.
It simply doesn't work when I try to free the memory that is used
by an object in my program...
I explicitly declared this object as null, and called System.gc, but it seems it isn't working.
What might be the reason?
This object uses a lot of memory. Therefore, I MUST destroy it after it's no longer
needed.Ok. I'll try to be more specific...
My "situation" seems something like that
class Program {
Xclass class1;
void method1() {
class1 = new Xclass();
} (End of class Program)
class Xclass {
Yclass class2;
Public Xclass( ) {
class2 = new Yclass();
add(class2);
} (end of class Xclass)
class Yclass {
Public Yclass(Container parent) {
(no explicit reference to Xclass or Program classes or any variable or instantiations of said classes);
} (end of class Yclass)
Well, I know that the gc is not being done because the first time I call method1 everything goes fine. But When I try it again an OutOfMemoryError happens...
I tried to do the following (I know, it's not elegant, but I just wanted to get some results):
void method1() {
class1 = null;
System.gc();
class1 = new Xclass();
Again it worked in the first time. But later... -
Strange garbage collector behaviour
Hello,
I am seeing quite a strange behaviour from the garbage collector in one of our applications.
The application is a standalone Java app, it receives requests over a TCP socket and responds to them. It is basically a kind of a cache before the database. There is a constant request flow of 10-100 requests per second. Average response time is below 50ms. It is running on a multiprocessor Sun machine, JDK 1.4.1_02.
The problem arises when the app has been running for a while. Depending on the allowed maximum memory size - with 256mb after about half a day, with 512mb after about a day, the garbage collector seems to be running most of the time. We turned on GC logging and from the log I can see that initially for a long period only the DefNew collector is used. The GC times are ~0.05sec then. Then after some time old generation collections start taking place. These collections take 3-4 seconds. The old gen collections then become more frequent until all that is going on, is one collection after another. About 3-4seconds for the collection, then after another 3-4 seconds the same thing again.
Can anyone please help in understanding what can cause this kind of behaviour? I am quite sure that the app is stable in a sense that it doesn't start to eat up extra memory at some point.
Any help greatly appreciated,
erik
Here are some excerpts from the GC log:
After startup:
100.264: [GC 100.264: [DefNew: 83488K->1290K(84800K), 0.0487560 secs] 87278K->5080K(259584K), 0.0490613 secs]
107.439: [GC 107.439: [DefNew: 83530K->1299K(84800K), 0.0526107 secs] 87320K->5178K(259584K), 0.0528313 secs]
111.554: [GC 111.554: [DefNew: 83539K->1207K(84800K), 0.0539021 secs] 87418K->5230K(259584K), 0.0541348 secs]
119.724: [GC 119.724: [DefNew: 83447K->1359K(84800K), 0.0561691 secs] 87470K->5382K(259584K), 0.0564463 secs]
125.576: [GC 125.576: [DefNew: 83599K->1366K(84800K), 0.0622342 secs] 87622K->5504K(259584K), 0.0624880 secs]
130.987: [GC 130.987: [DefNew: 83606K->1331K(84800K), 0.0586104 secs] 87744K->5607K(259584K), 0.0588732 secs]
138.695: [GC 138.695: [DefNew: 83571K->1296K(84800K), 0.0588720 secs] 87847K->5697K(259584K), 0.0591136 secs]
144.413: [GC 144.413: [DefNew: 83536K->1246K(84800K), 0.0607789 secs] 87937K->5790K(259584K), 0.0612128 secs]
150.661: [GC 150.661: [DefNew: 83486K->1279K(84800K), 0.0486299 secs] 88030K->5823K(259584K), 0.0488933 secs]
157.186: [GC 157.187: [DefNew: 83519K->1410K(84800K), 0.0545036 secs] 88063K->5954K(259584K), 0.0547557 secs]
162.937: [GC 162.937: [DefNew: 83650K->1230K(84800K), 0.0590144 secs] 88194K->5998K(259584K), 0.0592747 secs]
171.555: [GC 171.555: [DefNew: 83470K->1334K(84800K), 0.0554568 secs] 88238K->6101K(259584K), 0.0557090 secs]
175.416: [GC 175.416: [DefNew: 83574K->1315K(84800K), 0.0584964 secs] 88341K->6178K(259584K), 0.0587433 secs]
182.616: [GC 182.616: [DefNew: 83555K->1307K(84800K), 0.0709417 secs] 88418K->6234K(259584K), 0.0712034 secs]
And then in the end:
13177.7: [GC 13177.7: [DefNew: 82240K->82240K(84800K), 0.0000487 secs]13177.7: [Tenured: 95861K->96094K(174784K), 3.7160279 secs] 178101K->96094K(259584K), 3.7165109 secs]
13183.9: [GC 13183.9: [DefNew: 82240K->82240K(84800K), 0.0000459 secs]13183.9: [Tenured: 96094K->96268K(174784K), 3.6973634 secs] 178334K->96268K(259584K), 3.6978356 secs]
13193: [GC 13193: [DefNew: 82240K->82240K(84800K), 0.0000534 secs]13193: [Tenured: 96268K->95923K(174784K), 4.6233189 secs] 178508K->95923K(259584K), 4.6237995 secs]
13201.2: [GC 13201.2: [DefNew: 82240K->82240K(84800K), 0.0000531 secs]13201.2: [Tenured: 95923K->96100K(174784K), 3.7120306 secs] 178163K->96100K(259584K), 3.7125165 secs]
13208.6: [GC 13208.6: [DefNew: 82240K->82240K(84800K), 0.0000502 secs]13208.6: [Tenured: 96100K->96268K(174784K), 3.6950267 secs] 178340K->96268K(259584K), 3.6955072 secs]
13218.1: [GC 13218.1: [DefNew: 82240K->82240K(84800K), 0.0000582 secs]13218.1: [Tenured: 96268K->96442K(174784K), 3.7476890 secs] 178508K->96442K(259584K), 3.7481875 secs]
13225.8: [GC 13225.8: [DefNew: 82240K->82240K(84800K), 0.0002743 secs]13225.8: [Tenured: 96442K->96200K(174784K), 4.9092106 secs] 178682K->96200K(259584K), 4.9103437 secs]
13234.4: [GC 13234.4: [DefNew: 82240K->82240K(84800K), 0.0000541 secs]13234.4: [Tenured: 96200K->96409K(174784K), 3.7423712 secs] 178440K->96409K(259584K), 3.7428506 secs]
13240.6: [GC 13240.6: [DefNew: 82240K->82240K(84800K), 0.0000528 secs]13240.6: [Tenured: 96409K->96633K(174784K), 3.6245501 secs] 178649K->96633K(259584K), 3.6250124 secs]
13273.7: [GC 13273.7: [DefNew: 82240K->82240K(84800K), 0.0000651 secs]13273.7: [Tenured: 96633K->96799K(174784K), 3.7021988 secs] 178873K->96799K(259584K), 3.7027242 secs]
13283: [GC 13283: [DefNew: 82240K->82240K(84800K), 0.0000510 secs]13283: [Tenured: 96799K->96620K(174784K), 4.9944806 secs] 179039K->96620K(259584K), 4.9949444 secs]
I can provide the whole log if neccessary.The most likely cause of this problem is a memory leak in your application. As the memory reaches close to its limit the GC has to run for longer, more often to get free memory.
The runtime before going slow being proportional to the memory size.
Can you have the program log the System.freeMemory() and System.totalMemory()
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