Garbage Collection Weak References
Can someone please explain to me the point of Weak References.
here is what i understand
// we have a strong reference object
String strong = new String("i am a strong reference");
// we create a weak reference object
Reference wr = new WeakReference(strong);
Now what i have understood from my readings is that now when strong dereferences the object that was initially created the garbage collector deallocates the memory for that item.
but what is the point of a WeakReference?
This might be useful for you.
http://java.sun.com/developer/technicalArticles/ALT/RefObj/
Similar Messages
-
How strong ,soft ,weak ,phantom references are used in garbage collection
Hi
to all here.I have doubt that how garbage collection is deciding to cleaning up heap , and what are the roles of strong , soft , weak and phantom reference in garbage collection, i went throgh sun's java docs but i couldn't get any clear idea about those , please can anyone explain me with nice examples for which i will be really thankful.See:
http://java.sun.com/developer/technicalArticles/ALT/RefObj/ -
Find out references to objects (garbage collection)
Is there an easy way to find out, which references prevent the garbage collector from collecting my old objects, which I expect should be collected? Something like System.out.println(...)
if you just want an object to be garbage collected, just
make sure you de-reference is completely.CMueller obviously doesn't know which references prevent garbage collection so naturally he cannot set those references to null, now can he?
o = null; // sets the value to null and drops all the referencesThat is simply not true. Removing a reference to an object doesn't affect any other references to that object.
Object o1,o2;
//create an object and make o1 reference it
o1=new Object();
//make o2 reference the same object as o1 references
o2=o1;
//now there are two references to the object
//make o1 reference null
o1=null;
//at this point there is still one reference (o2) to
//the object and therefore the object is NOT garbage
//which means that it can NOT be collected by the GC- Marcus Sundman -
A question about JNI references, persistence, and garbage collection
I am writing a library to allow our Java developers to access C functions in our product. I want people on the Java side to be able to instantiate instances of a new object (on the C side), say "Map", and I want those objects to persist until they are destroyed on the Java side. I am thinking of creating a wrapper for the native methods, which stores an identifier for the instance of an object. When the C object is accessed, the identifier is passed to the C code which looks up the correct object in a table. I understand that if I use the NewGlobalReference call in JNI I can get objects to persist.
When it is time for garbage collection I plan to override finalize() to call the C code and tell it to remove the Global Reference.
Here's what I have in mind
public class JMap() {
private static int id;
static {
System.loadLibrary("libMap");
/*Call C method which instantiates object and creates a GlobalReference
which is stored in table. Returns ID for reference*/
id = _init();
public void setSize(int x, int y) {
_setSize(id, x, y);
public void finalize() {
_finalize(id);
super.finalize();
private native int _init();
/*calls DeleteGlobalReference for the reference matching this id*/
private native void _finalize(int id);
private native void _setSize(int id, int x, int y);
}Is this the right thing to do? Have I understood the way JNI works with regard to GlobalReferences?
Any comments, tips or pointers would be appreciated :)This probably should have been posted in the Native Methods sub-forum, I have reposted there:
http://forum.java.sun.com/thread.jspa?threadID=657667
Mods please delete this post :) -
Nested object reference after garbage collection
I have a question about how GC works.
Assume I have a Class A which has a reference to class B inside it. I create a object of class B and assign to member variable of class A.
Now when obja is no longer needed, I set it null. And when GC runs, the object will be removed from memory. But should I also need to explicitly set objb to null. If i don't set it, will it also get garbage collected when obja is being removed from memory?
public class ClassA {
private ClassB objB = new ClassB();
private static void main(String args[]) {
ClassA obja = new ClassA();
obja = null;
}801625 wrote:
But should I also need to explicitly set objb to null.No.
If i don't set it, will it also get garbage collected when obja is being removed from memory?If there are no other references outside of classA to the object referenced by objB (in your case an instance of ClassB) then it will be garbage collected.
Note - the only time one needs to set a reference to null is if one wants the object it references to be eligible for GC before the reference goes out of scope. There is a slight complication to this - depending on the JVM implementation, if a reference is defined in a block internal to a method then even though it goes out of scope when execution goes out of the block anything it references may not be eligible for GC until the method exits. -
Are weak references cleared with soft ones?
Suppose a program holds both weak and soft references to an object X. Suppose the virtual machine clears all the soft references at once, making X weakly reachable. Is the virtual machine guaranteed to clear all the weak references next before normal execution resumes?
I ask because I am setting up an automatic interning system for immutable objects of a certain class that will guarantee that at most one object of a given value is reachable by the rest of the program at one time but will allow objects to be garbage collected if necessary. I need to decide what reference object(s) to keep to each interned object. If I keep only a weak reference, objects will be discarded at the whim of the virtual machine; I would prefer to keep them around longer so they don't have to be recreated so many times. If I keep only a soft reference, I am concerned that another part of the program might keep a weak reference. If the answer to my question above is "no", the soft reference could be cleared and the interning system could create a second object with the same value while the first is still accessible via the weak reference. It seems safest to keep both a soft reference and a weak reference and only recreate the object if the weak reference has been cleared.Softs hang around until memory needs dictate theygo.
In my experience (Apple's 1.4 VM) this appears to be
as soon as GC is run, making them effectively
useless. Maybe VMs have improved.Not in my experience (Sun 1.4 VM). Soft references hang around forever. I had to stuff my class with bloat to make the instance larger, then change the VM heap size to get it to start collecting my soft references. Whereas the weak references are dumped ASAP. Inside scoop has it that finalizers will delay object collection a bit so be careful of that.
Also the only guarantee is that soft is cleared before weak when they refer to the same object. in my experience weak references go quickly. Like at the first GC when they are weak. You can not depend on any timing with respect to when the weak will be cleared. I don't think the spec even guarantees that soft will be enqueued before weak. Im not sure on that point. -
Soft/Weak References: rule of thumbs?
After reading <a target="extern" href="http://java.sun.com/developer/technicalArticles/ALT/RefObj/index.html">Reference Objects and Garbage Collection</a> i browsed my code and replaced my listener containers with versions that store WeakReference objects. The main idea is to avoid memory leaks by storing references to objects that are not needed anymore (the listener container is the only strong reference left).
Another rule is to use SoftReferences for caches. But I haven't figured out a good way of implementing it (for caches that fill itself with one single SQL statement).
Are there any other examples where it's good advice to use Soft/Weak References?For listeners, you have to make sure that the listener object is hard referenced - which is usually the case. After you release the listener object from the main application/object/thread, because it's finished or you don't need it anymore, the listener holder should not hold on to such references to avoid OutOfMemoryExceptions. Of course, the best way is always to unregister a listener, but unfortunately, we're not living in a perfect world. No listener is forced to unregister, they can simple forget to unregister. For this reason, it's better to tell the listener: if you register yourself, you should know that you are just referenced via WeakReferences. If the listener suddenly doesn't get listener events, this is a coding error which can be traced and fixed. But if a listener forgets to unregister itself, the resulting memory bloat is much harder to trace.
SQL table caches are difficult. On one hand you want to cache the data, on the other, you want to free this cache memory (temporarily) for more important memory usage. It's always a trade off between 2 advantages. If performance is not the big issue, but you get OutOfMemoryExceptions, then this is critical for the application to continue working. Better a little slower than not at all ... ;-) -
Eclipselink log levels issue with weak references
Hi all,
Is it possible to get null pointer exceptions if the log level in eclipselink is set to FINEST and you are logging a weak reference probably in a IdentityWeakReferenceMap and getting a null pointer exception because the weak ref has been garbage collected ?
-Prashanth.I am getting Nullpointer exception when I set log level to FINER or FINEST in persistence.xml.
DisRootEntityRef entity which is seen in below log has week reference in erml.
Here is the exception full trace:
EL Warning: 2010-05-31 17:06:52.328--UnitOfWork(19025200)--Thread(Thread[)--java.lang.NullPointerException
at oracle.communications.platform.entity.impl.DisRootEntityRefDAO.getRootEntity(DisRootEntityRefDAO.java:300)
at oracle.communications.platform.entity.impl.DisRootEntityRefDAO.getToString(DisRootEntityRefDAO.java:591)
at oracle.communications.platform.entity.impl.DisRootEntityRefDAO.toString(DisRootEntityRefDAO.java:584)
at java.text.MessageFormat.subformat(MessageFormat.java:1246)
at java.text.MessageFormat.format(MessageFormat.java:836)
at java.text.Format.format(Format.java:140)
at java.text.MessageFormat.format(MessageFormat.java:812)
at org.eclipse.persistence.internal.localization.EclipseLinkLocalization.buildMessage(EclipseLinkLocalization.java:77)
at org.eclipse.persistence.internal.localization.TraceLocalization.buildMessage(TraceLocalization.java:30)
at org.eclipse.persistence.logging.AbstractSessionLog.formatMessage(AbstractSessionLog.java:801)
at org.eclipse.persistence.platform.server.ServerLog.log(ServerLog.java:71)
at org.eclipse.persistence.internal.sessions.AbstractSession.log(AbstractSession.java:2571)
at org.eclipse.persistence.internal.sessions.AbstractSession.log(AbstractSession.java:3664)
at org.eclipse.persistence.internal.sessions.AbstractSession.log(AbstractSession.java:3636)
at org.eclipse.persistence.internal.sessions.AbstractSession.log(AbstractSession.java:3612)
at org.eclipse.persistence.internal.sessions.AbstractSession.log(AbstractSession.java:3534)
at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.logDebugMessage(UnitOfWorkImpl.java:5397)
at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.registerExistingObject(UnitOfWorkImpl.java:3874)
at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.registerExistingObject(UnitOfWorkImpl.java:3844)
at org.eclipse.persistence.queries.ObjectBuildingQuery.registerIndividualResult(ObjectBuildingQuery.java:362)
at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildWorkingCopyCloneNormally(ObjectBuilder.java:588)
at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildObjectInUnitOfWork(ObjectBuilder.java:549)
at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildObject(ObjectBuilder.java:489)
at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildObject(ObjectBuilder.java:441)
at org.eclipse.persistence.queries.ObjectLevelReadQuery.buildObject(ObjectLevelReadQuery.java:635)
at org.eclipse.persistence.queries.ReadAllQuery.registerResultInUnitOfWork(ReadAllQuery.java:838)
at org.eclipse.persistence.queries.ReadAllQuery.executeObjectLevelReadQuery(ReadAllQuery.java:464)
at org.eclipse.persistence.queries.ObjectLevelReadQuery.executeDatabaseQuery(ObjectLevelReadQuery.java:997)
at org.eclipse.persistence.queries.DatabaseQuery.execute(DatabaseQuery.java:670)
at org.eclipse.persistence.queries.ObjectLevelReadQuery.execute(ObjectLevelReadQuery.java:958)
at org.eclipse.persistence.queries.ReadAllQuery.execute(ReadAllQuery.java:432)
at org.eclipse.persistence.queries.ObjectLevelReadQuery.executeInUnitOfWork(ObjectLevelReadQuery.java:1021)
at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.internalExecuteQuery(UnitOfWorkImpl.java:2858)
at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1225)
at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1207)
at org.eclipse.persistence.internal.indirection.QueryBasedValueHolder.instantiate(QueryBasedValueHolder.java:85)
at org.eclipse.persistence.internal.indirection.QueryBasedValueHolder.instantiate(QueryBasedValueHolder.java:75)
at org.eclipse.persistence.internal.indirection.DatabaseValueHolder.getValue(DatabaseValueHolder.java:83)
at org.eclipse.persistence.internal.indirection.UnitOfWorkValueHolder.instantiateImpl(UnitOfWorkValueHolder.java:161)
at org.eclipse.persistence.internal.indirection.UnitOfWorkValueHolder.instantiate(UnitOfWorkValueHolder.java:230)
at org.eclipse.persistence.internal.indirection.DatabaseValueHolder.getValue(DatabaseValueHolder.java:83)
at org.eclipse.persistence.indirection.IndirectList.buildDelegate(IndirectList.java:237)
at org.eclipse.persistence.indirection.IndirectList.getDelegate(IndirectList.java:397)
at org.eclipse.persistence.indirection.IndirectList$1.(IndirectList.java:525)
at org.eclipse.persistence.indirection.IndirectList.listIterator(IndirectList.java:524)
at org.eclipse.persistence.indirection.IndirectList.iterator(IndirectList.java:488)
at oracle.communications.platform.persistence.impl.PomsArrayList.iterator(PomsArrayList.java:598)
at oracle.communications.platform.entity.impl.DisResultGroupDAO.getRootEntities(DisResultGroupDAO.java:765)
at oracle.communications.integrity.scanCartridges.sdk.RootEntityLoaderImpl.(RootEntityLoaderImpl.java:37)
at oracle.communications.integrity.scanCartridges.sdk.BaseDiscrepancyDetectionController.init(BaseDiscrepancyDetectionController.java:71)
at oracle.communications.integrity.scanCartridges.sdk.BaseDiscrepancyDetectionController.invoke(BaseDiscrepancyDetectionController.java:41)
at oracle.communications.integrity.cartridges.ciscoextensioncartridge.detectionplugins.ciscodiscrepancydetectionsample.CiscoDiscrepancyDetectionSampleMessageDrivenBean.onMessage(CiscoDiscrepancyDetectionSampleMessageDrivenBean.java:109)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at com.bea.core.repackaged.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:310)
at com.bea.core.repackaged.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:182)
at com.bea.core.repackaged.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:149)
at com.bea.core.repackaged.springframework.aop.support.DelegatingIntroductionInterceptor.doProceed(DelegatingIntroductionInterceptor.java:131)
at com.bea.core.repackaged.springframework.aop.support.DelegatingIntroductionInterceptor.invoke(DelegatingIntroductionInterceptor.java:119)
at com.bea.core.repackaged.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
at com.bea.core.repackaged.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:89)
at com.bea.core.repackaged.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
at com.bea.core.repackaged.springframework.aop.support.DelegatingIntroductionInterceptor.doProceed(DelegatingIntroductionInterceptor.java:131)
at com.bea.core.repackaged.springframework.aop.support.DelegatingIntroductionInterceptor.invoke(DelegatingIntroductionInterceptor.java:119)
at com.bea.core.repackaged.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
at com.bea.core.repackaged.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204)
at $Proxy343.onMessage(Unknown Source)
at weblogic.ejb.container.internal.MDListener.execute(MDListener.java:466)
at weblogic.ejb.container.internal.MDListener.transactionalOnMessage(MDListener.java:371)
at weblogic.ejb.container.internal.MDListener.onMessage(MDListener.java:327)
at weblogic.jms.client.JMSSession.onMessage(JMSSession.java:4585)
at weblogic.jms.client.JMSSession.execute(JMSSession.java:4271)
at weblogic.jms.client.JMSSession.executeMessage(JMSSession.java:3747)
at weblogic.jms.client.JMSSession.access$000(JMSSession.java:114)
at weblogic.jms.client.JMSSession$UseForRunnable.run(JMSSession.java:5096)
at weblogic.work.SelfTuningWorkManagerImpl$WorkAdapterImpl.run(SelfTuningWorkManagerImpl.java:516)
at weblogic.work.ExecuteThread.execute(ExecuteThread.java:201)
at weblogic.work.ExecuteThread.run(ExecuteThread.java:173)
oracle.communications.integrity.cartridges.ciscoextensioncartridge.detectionplugins.ciscodiscrepancydetectionsample.CiscoDiscrepancyDetectionSampleMessageDrivenBean
java.lang.NullPointerException
at oracle.communications.platform.entity.impl.DisRootEntityRefDAO.getRootEntity(DisRootEntityRefDAO.java:300)
at oracle.communications.platform.entity.impl.DisRootEntityRefDAO.getToString(DisRootEntityRefDAO.java:591)
at oracle.communications.platform.entity.impl.DisRootEntityRefDAO.toString(DisRootEntityRefDAO.java:584)
at java.text.MessageFormat.subformat(MessageFormat.java:1246)
at java.text.MessageFormat.format(MessageFormat.java:836)
at java.text.Format.format(Format.java:140)
at java.text.MessageFormat.format(MessageFormat.java:812)
at org.eclipse.persistence.internal.localization.EclipseLinkLocalization.buildMessage(EclipseLinkLocalization.java:77)
at org.eclipse.persistence.internal.localization.TraceLocalization.buildMessage(TraceLocalization.java:30)
at org.eclipse.persistence.logging.AbstractSessionLog.formatMessage(AbstractSessionLog.java:801)
at org.eclipse.persistence.platform.server.ServerLog.log(ServerLog.java:71)
at org.eclipse.persistence.internal.sessions.AbstractSession.log(AbstractSession.java:2571)
at org.eclipse.persistence.internal.sessions.AbstractSession.log(AbstractSession.java:3664)
at org.eclipse.persistence.internal.sessions.AbstractSession.log(AbstractSession.java:3636)
at org.eclipse.persistence.internal.sessions.AbstractSession.log(AbstractSession.java:3612)
at org.eclipse.persistence.internal.sessions.AbstractSession.log(AbstractSession.java:3534)
at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.logDebugMessage(UnitOfWorkImpl.java:5397)
at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.registerExistingObject(UnitOfWorkImpl.java:3874)
at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.registerExistingObject(UnitOfWorkImpl.java:3844)
at org.eclipse.persistence.queries.ObjectBuildingQuery.registerIndividualResult(ObjectBuildingQuery.java:362)
at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildWorkingCopyCloneNormally(ObjectBuilder.java:588)
at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildObjectInUnitOfWork(ObjectBuilder.java:549)
at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildObject(ObjectBuilder.java:489)
at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildObject(ObjectBuilder.java:441)
at org.eclipse.persistence.queries.ObjectLevelReadQuery.buildObject(ObjectLevelReadQuery.java:635)
at org.eclipse.persistence.queries.ReadAllQuery.registerResultInUnitOfWork(ReadAllQuery.java:838)
at org.eclipse.persistence.queries.ReadAllQuery.executeObjectLevelReadQuery(ReadAllQuery.java:464)
at org.eclipse.persistence.queries.ObjectLevelReadQuery.executeDatabaseQuery(ObjectLevelReadQuery.java:997)
at org.eclipse.persistence.queries.DatabaseQuery.execute(DatabaseQuery.java:670)
at org.eclipse.persistence.queries.ObjectLevelReadQuery.execute(ObjectLevelReadQuery.java:958)
at org.eclipse.persistence.queries.ReadAllQuery.execute(ReadAllQuery.java:432)
at org.eclipse.persistence.queries.ObjectLevelReadQuery.executeInUnitOfWork(ObjectLevelReadQuery.java:1021)
at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.internalExecuteQuery(UnitOfWorkImpl.java:2858)
at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1225)
at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1207)
at org.eclipse.persistence.internal.indirection.QueryBasedValueHolder.instantiate(QueryBasedValueHolder.java:85)
at org.eclipse.persistence.internal.indirection.QueryBasedValueHolder.instantiate(QueryBasedValueHolder.java:75)
at org.eclipse.persistence.internal.indirection.DatabaseValueHolder.getValue(DatabaseValueHolder.java:83)
at org.eclipse.persistence.internal.indirection.UnitOfWorkValueHolder.instantiateImpl(UnitOfWorkValueHolder.java:161)
at org.eclipse.persistence.internal.indirection.UnitOfWorkValueHolder.instantiate(UnitOfWorkValueHolder.java:230)
at org.eclipse.persistence.internal.indirection.DatabaseValueHolder.getValue(DatabaseValueHolder.java:83)
at org.eclipse.persistence.indirection.IndirectList.buildDelegate(IndirectList.java:237)
at org.eclipse.persistence.indirection.IndirectList.getDelegate(IndirectList.java:397)
at org.eclipse.persistence.indirection.IndirectList$1.(IndirectList.java:525)
at org.eclipse.persistence.indirection.IndirectList.listIterator(IndirectList.java:524)
at org.eclipse.persistence.indirection.IndirectList.iterator(IndirectList.java:488)
at oracle.communications.platform.persistence.impl.PomsArrayList.iterator(PomsArrayList.java:598)
at oracle.communications.platform.entity.impl.DisResultGroupDAO.getRootEntities(DisResultGroupDAO.java:765)
at oracle.communications.integrity.scanCartridges.sdk.RootEntityLoaderImpl.(RootEntityLoaderImpl.java:37)
at oracle.communications.integrity.scanCartridges.sdk.BaseDiscrepancyDetectionController.init(BaseDiscrepancyDetectionController.java:71)
at oracle.communications.integrity.scanCartridges.sdk.BaseDiscrepancyDetectionController.invoke(BaseDiscrepancyDetectionController.java:41)
at oracle.communications.integrity.cartridges.ciscoextensioncartridge.detectionplugins.ciscodiscrepancydetectionsample.CiscoDiscrepancyDetectionSampleMessageDrivenBean.onMessage(CiscoDiscrepancyDetectionSampleMessageDrivenBean.java:109)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at com.bea.core.repackaged.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:310)
at com.bea.core.repackaged.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:182)
at com.bea.core.repackaged.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:149)
at com.bea.core.repackaged.springframework.aop.support.DelegatingIntroductionInterceptor.doProceed(DelegatingIntroductionInterceptor.java:131)
at com.bea.core.repackaged.springframework.aop.support.DelegatingIntroductionInterceptor.invoke(DelegatingIntroductionInterceptor.java:119)
at com.bea.core.repackaged.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
at com.bea.core.repackaged.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:89)
at com.bea.core.repackaged.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
at com.bea.core.repackaged.springframework.aop.support.DelegatingIntroductionInterceptor.doProceed(DelegatingIntroductionInterceptor.java:131)
at com.bea.core.repackaged.springframework.aop.support.DelegatingIntroductionInterceptor.invoke(DelegatingIntroductionInterceptor.java:119)
at com.bea.core.repackaged.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
at com.bea.core.repackaged.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204)
at $Proxy343.onMessage(Unknown Source)
at weblogic.ejb.container.internal.MDListener.execute(MDListener.java:466)
at weblogic.ejb.container.internal.MDListener.transactionalOnMessage(MDListener.java:371)
at weblogic.ejb.container.internal.MDListener.onMessage(MDListener.java:327)
at weblogic.jms.client.JMSSession.onMessage(JMSSession.java:4585)
at weblogic.jms.client.JMSSession.execute(JMSSession.java:4271)
at weblogic.jms.client.JMSSession.executeMessage(JMSSession.java:3747)
at weblogic.jms.client.JMSSession.access$000(JMSSession.java:114)
at weblogic.jms.client.JMSSession$UseForRunnable.run(JMSSession.java:5096)
at weblogic.work.SelfTuningWorkManagerImpl$WorkAdapterImpl.run(SelfTuningWorkManagerImpl.java:516)
at weblogic.work.ExecuteThread.execute(ExecuteThread.java:201)
at weblogic.work.ExecuteThread.run(ExecuteThread.java:173) -
Weak References in Listener Lists
I've found a common source of memory leaks is when objects that add themselves to listener lists forget to remove themselves when they are done.
It would be nice to generalize and say that listener lists should contain weak references, but there are probably valid cases where a listener's only valid reference is through the listener list.
It would be nice to extend the listener pattern so that the listener could specify if they should be referenced weakly, for examplemodel.addChangeListener(this, true)where true indicates the reference to the listener should be weak.
In some cases like the Model View Controller pattern, it probably makes sense that whenever a view listens to a model it should be weakly referenced. For example, when you construct a JTable and pass the model as a parameter to the constructor, the JTable should always specify a weak reference when it listens to the model.
I think supporting a feature like this in the listener APIs could help reduce the potential for memory leaks and make code a little more maintainable.There was another time that I dabbled in this idea.
But it always comes back to objects cleaning up
after themselves. Now if its not your code and you
cant ensure good behavior, then perhaps there is
cause. But I'd keep an assert and report the issue
if I saw it trigger.What would fire the assert? The Listener will never be garbage collected while it is listening to something. I assume that you are talking about when the listener is a Swing Object like a JFrame. I don't really like to use gui components as listeners.
If you have to write a clean up method, it kind of defeats the value of having automatic garbage collection to a degree. I like to be able to let my Objects just fall out of scope or just become unreachable when they are no longer needed without having to actively manage their deallocation. -
Hi,
We are having a problem where an RMI object is not being garbage collected. A fellow developer has suggested that since the JMX server has a reference to the object it will never be garbage collected. Does anyone know if the JMX server keeps a weak reference to an object or to garbage collect the object you must unload it from the JMX server?Hi,
We are having a problem where an RMI object is not
ot being garbage collected. A fellow developer has
suggested that since the JMX server has a reference
to the object it will never be garbage collected.
Does anyone know if the JMX server keeps a weak
reference to an object or to garbage collect the
object you must unload it from the JMX server?not sure exactly what you are saying; but jmx deals with mbeans only. if your remote object is not an mbean object, it would have nothing to do with jmx. to kill an mbean object, use jms to unload it. -
Weak reference for MapListeners?
I create objects which implement MapListener and then I register those objects with a CQC. If at some later time the only reference to that object is from the CQC, I would like that object to be garbage collected and the MapListener obviously unregistered. My understanding is that if I create objects and register them as MapListeners, they'll never be GC'd unless I unregister them. Is that right? For my application I'd like the CQC's reference to my MapListener to be a weak reference. Am I correct about all this? Can anyone suggest a work-around for me?
Thanks,
AndrewHi Andrew,
CQC (or any of the named cache implementations for that matter) isn't designed to treat listeners weakly, so there really is no clean way of doing what you are asking that I know of. The only thing I can think of is to wrap the other references to your listener object to incorporate a finalizer that will then turn around and unregister the "weak" listener, upon finalization.
For example:
import com.tangosol.net.NamedCache;
import com.tangosol.util.MapEvent;
import com.tangosol.util.MapListener;
import java.util.Iterator;
import java.util.HashSet;
import java.util.Set;
public class MyListener
implements MapListener
* The map listener object to wrap.
* @param listener the map listener
public MyListener(MapListener listener)
m_listenerInternal = listener;
* Register this listener with the specified cache.
* @param cache the named cache to register this listener with
public void registerWeakListener(NamedCache cache)
cache.addMapListener(getListenerInternal());
m_setCache.add(cache);
// ----- MapListener interface ----------------------------------------
* {@inheritDoc}
public void entryInserted(MapEvent evt)
getListenerInternal().entryInserted(evt);
* {@inheritDoc}
public void entryUpdated(MapEvent evt)
getListenerInternal().entryUpdated(evt);
* {@inheritDoc}
public void entryDeleted(MapEvent evt)
getListenerInternal().entryDeleted(evt);
// ----- internal -----------------------------------------------------
protected MapListener getListenerInternal()
return m_listenerInternal;
private MapListener m_listenerInternal;
private Object m_finalizer = new Object()
public void finalize()
MapListener listener = m_listenerInternal;
for (Iterator iter = m_setCache.iterator(); iter.hasNext(); )
((NamedCache) iter.next()).removeMapListener(listener);
private Set m_setCache = new HashSet();
} -
Hotspot core dumping during JVM garbage collection ?
We have an application which calls a 3rd party supplied server API which has recently been upgraded to use Java 1.5
We are getting the following error reported by our client application. The application is also now running Java 1.5 but references many classes in jar files which would have quite old code in.
The supplier of the API has stated that the problem requires us to recompile all our jar files using v 1.5 ( including things like jconnect and jms ?!?!? ). This sounds like a bit of a cop-out to me, not to mention being impossible since we don't have the source for things like jconnect.
I suspect that there is a garbage collection problem at the bottom of all this, but I'm not sure how I can "prove" this, nor do I currently have any real clue as to how to fix any GC problem that may exist.
The application is supposed to wait for a message on a MQSeries queue and then transforms it via Xalan XSLT and sends it to a Server application. I've tried playing around with heap sizes etc but that just seems to make it worse. If I leave it at the settings that the previous version used then the client at least manages to process a couple of messages before core dumping. There doesn't seem to be a consistent trigger event to cause the core dump ( it's not a message arriving on a queue for example ) but it does seem to be fairly consistent timewise, i.e. after
Any ideas gratefully accepted.
Here's a logfile excerpt from my applications showing the Hotspot error message :
=====================================================================================
08-Jul-2008 10:01:05 Waiting for messages from COLT.BBFS
08-Jul-2008 10:02:05 Waiting for messages from COLT.BBFS
08-Jul-2008 10:03:05 Waiting for messages from COLT.BBFS
405.815: [GC [PSYoungGen: 17331K->9244K(37632K)] 111702K->103615K(192128K), 0.1615910 secs]
405.977: [Full GC#
# An unexpected error has been detected by HotSpot Virtual Machine:
# SIGBUS (0xa) at pc=0xfe141348, pid=2600, tid=8
# Java VM: Java HotSpot(TM) Server VM (1.5.0_03-b07 mixed mode)
# Problematic frame:
# V [libjvm.so+0x141348]
# An error report file with more information is saved as hs_err_pid2600.log
# If you would like to submit a bug report, please visit:
# http://java.sun.com/webapps/bugreport/crash.jsp
=====================================================================================
The logfile referred to in the error message contains the following.
=====================================================================================
# An unexpected error has been detected by HotSpot Virtual Machine:
# SIGBUS (0xa) at pc=0xfe141348, pid=2600, tid=8
# Java VM: Java HotSpot(TM) Server VM (1.5.0_03-b07 mixed mode)
# Problematic frame:
# V [libjvm.so+0x141348]
--------------- T H R E A D ---------------
Current thread (0x001484d8): VMThread [id=8]
siginfo:si_signo=10, si_errno=0, si_code=1, si_addr=0x0000080f
Registers:
O0=0x00487588 O1=0xfe7d6454 O2=0x000079b0 O3=0x00007800
O4=0x00008868 O5=0x00147d48 O6=0xf8781460 O7=0xfe0f7938
G1=0xe52aaae8 G2=0x00000003 G3=0x00000003 G4=0x001484d8
G5=0xf8781d98 G6=0x00000002 G7=0xf8781d98 Y=0x805683e2
PC=0xfe141348 nPC=0xfe14134c
Top of Stack: (sp=0xf8781460)
0xf8781460: fe786000 00c6ba20 fe10013c e54bab68
0xf8781470: 0000080f e54bab6c 0000080f 00000004
0xf8781480: 00487588 00000134 e54bab6c 00000004
0xf8781490: 00000001 00000000 f87814c0 fe17aef4
0xf87814a0: fe6485b4 fe7d899c 001484d8 0011da40
0xf87814b0: 00148988 00148c10 00148d7c f8781880
0xf87814c0: 007c3389 007c3c0e 00000f87 00008868
0xf87814d0: 00008800 00487588 fe141310 fe7d6454
Instructions: (pc=0xfe141348)
0xfe141338: ec 06 c0 1a 80 a5 a0 00 22 40 00 0a ba 07 60 01
0xfe141348: f2 05 a0 00 ae 0e 60 03 80 a5 e0 03 22 40 00 05
Stack: [0xf8702000,0xf8781d98), sp=0xf8781460, free space=509k
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [libjvm.so+0x141348]
V [libjvm.so+0x17aefc]
V [libjvm.so+0x2d557c]
V [libjvm.so+0x300ef8]
V [libjvm.so+0x301e84]
V [libjvm.so+0x2ff950]
V [libjvm.so+0x29df30]
V [libjvm.so+0x362b44]
V [libjvm.so+0x6436f0]
VM_Operation (0xe03012b0): parallel gc system gc, mode: safepoint, requested by thread 0x0031bca0
--------------- P R O C E S S ---------------
Java Threads: ( => current thread )
0x00b2c028 JavaThread "Thread-4" [_thread_in_native, id=85]
0x007f5048 JavaThread "Thread-0" [_thread_blocked, id=84]
0x00c27cf0 JavaThread "Notification Delivery" [_thread_blocked, id=81]
0x0026fa08 JavaThread "RMI LeaseChecker" daemon [_thread_blocked, id=73]
0x00821048 JavaThread "RMI RenewClean-[162.11.2.32:44425]" daemon [_thread_blocked, id=70]
0x0031bca0 JavaThread "GC Daemon" daemon [_thread_blocked, id=67]
0x00cd5d28 JavaThread "RMI Reaper" [_thread_blocked, id=66]
0x003c9300 JavaThread "Timer-0" daemon [_thread_blocked, id=65]
0x00929fe0 JavaThread "RMI TCP Accept-0" daemon [_thread_in_native, id=64]
0x0089bf18 JavaThread "SeedGenerator Thread" daemon [_thread_blocked, id=42]
0x00c47248 JavaThread "Pool thread #7" daemon [_thread_blocked, id=38]
0x00c466a0 JavaThread "Pool thread #6" daemon [_thread_blocked, id=37]
0x00311850 JavaThread "Pool thread #5" daemon [_thread_blocked, id=36]
0x00287a40 JavaThread "Pool thread #4" daemon [_thread_blocked, id=35]
0x00286e98 JavaThread "Pool thread #3" daemon [_thread_blocked, id=34]
0x00c134b0 JavaThread "Pool thread #2" daemon [_thread_blocked, id=33]
0x00ad09e0 JavaThread "Pool thread #1" daemon [_thread_blocked, id=32]
0x00286cd8 JavaThread "PoolThreadManager" daemon [_thread_blocked, id=31]
0x00c129e0 JavaThread "Channel Reaper" daemon [_thread_blocked, id=30]
0x00c669e8 JavaThread "ORB Daemon Thread" daemon [_thread_blocked, id=29]
0x00b10170 JavaThread "Worker for ServerProtocol: (iiop) /0.0.0.0:20168" daemon [_thread_blocked, id=22]
0x008a17e0 JavaThread "Syn~ Client" daemon [_thread_blocked, id=21]
0x003dc378 JavaThread "PoolScavenger0" daemon [_thread_blocked, id=20]
0x0015a928 JavaThread "Low Memory Detector" daemon [_thread_blocked, id=15]
0x00159880 JavaThread "CompilerThread1" daemon [_thread_blocked, id=14]
0x00158a18 JavaThread "CompilerThread0" daemon [_thread_blocked, id=13]
0x00157b98 JavaThread "AdapterThread" daemon [_thread_blocked, id=12]
0x00156dc8 JavaThread "Signal Dispatcher" daemon [_thread_blocked, id=11]
0x0014ccd8 JavaThread "Finalizer" daemon [_thread_blocked, id=10]
0x0014ad90 JavaThread "Reference Handler" daemon [_thread_blocked, id=9]
0x00038238 JavaThread "main" [_thread_in_native, id=1]
Other Threads:
=>0x001484d8 VMThread [id=8]
0x0015c3b0 WatcherThread [id=16]
VM state:at safepoint (normal execution)
VM Mutex/Monitor currently owned by a thread: ([mutex/lock_event])
[0x00037728/0x00037758] Threads_lock - owner thread: 0x001484d8
[0x00033650/0x00037ba8] Heap_lock - owner thread: 0x0031bca0
Heap
PSYoungGen total 37632K, used 9244K [0xf2eb0000, 0xf7ba0000, 0xf8400000)
eden space 28352K, 0% used [0xf2eb0000,0xf2eb0000,0xf4a60000)
from space 9280K, 99% used [0xf4a60000,0xf5367080,0xf5370000)
to space 25216K, 0% used [0xf6300000,0xf6300000,0xf7ba0000)
PSOldGen total 154496K, used 94371K [0xe8400000, 0xf1ae0000, 0xf2eb0000)
object space 154496K, 61% used [0xe8400000,0xee028e78,0xf1ae0000)
PSPermGen total 35584K, used 18260K [0xe4400000, 0xe66c0000, 0xe8400000)
object space 35584K, 51% used [0xe4400000,0xe55d5158,0xe66c0000)
Dynamic libraries:
0x00010000 /dsdvlp/java/jvm/jdk1.5.0_03/bin/java
0xff350000 /usr/lib/libthread.so.1
0xff340000 /usr/lib/libdl.so.1
0xff200000 /usr/lib/libc.so.1
0xff390000 /usr/platform/SUNW,Sun-Fire-880/lib/libc_psr.so.1
0xfe000000 /dsdvlp/java/jvm/jdk1.5.0_03/jre/lib/sparc/server/libjvm.so
0xff1e0000 /usr/lib/libsocket.so.1
0xff2d0000 /usr/lib/libsched.so.1
0xff1b0000 /usr/lib/libCrun.so.1
0xff160000 /usr/lib/libm.so.1
0xff080000 /usr/lib/libnsl.so.1
0xff060000 /usr/lib/libmp.so.2
0xff030000 /dsdvlp/java/jvm/jdk1.5.0_03/jre/lib/sparc/native_threads/libhpi.so
0xfdfc0000 /dsdvlp/java/jvm/jdk1.5.0_03/jre/lib/sparc/libverify.so
0xfdf80000 /dsdvlp/java/jvm/jdk1.5.0_03/jre/lib/sparc/libjava.so
0xfdf50000 /dsdvlp/java/jvm/jdk1.5.0_03/jre/lib/sparc/libzip.so
0xfb7e0000 /usr/lib/locale/en_GB.ISO8859-1/en_GB.ISO8859-1.so.2
0xe4190000 /dsdvlp/java/jvm/jdk1.5.0_03/jre/lib/sparc/libnet.so
0xe3bd0000 /dsdvlp/lib/5/libSolarisNatives.so
0xe3e90000 /dsdvlp/java/jvm/jdk1.5.0_03/jre/lib/sparc/librmi.so
VM Arguments:
jvm_args: -Djava.ext.dirs=/dsdvlp/java/tmijar/firs7/lib/cli:/dsdvlp/java/tmijar/firs7/lib/cli/ext:/dsdvlp/java/tmijar/firs7/lib/cmn/OpenORB:/dsdvlp/java/tmijar/firs7/lib/cmn/OpenORB/ext:/dsdvlp/java/tmijar/firs7/lib/cmn:/dsdvlp/java/tmijar/firs7/lib/cmn/ext:/dsdvlp/java/tmijar/firs7/daemonlib -Duser.dir=/dsdvlp/java/tmijar/firs7 -Dopenorb.config=file:/dsdvlp/java/tmijar/firs7/configs/OpenORB/config/SynOpenORB.xml -Dopenorb.home=file:/dsdvlp/java/tmijar/firs7/configs/OpenORB -Dcom.coexis.syn.general.orbbinding=com.coexis.syn.general.orbbinding.openorb.OpenORBBinding_1_4 -Dsun.rmi.dgc.client.gcInterval=360000 -Dsun.rmi.dgc.server.gcInterval=360000000 -Xms32m -Xmx256m -Dcom.coexis.syn.clientcommandsconfiglocation=file://localhost//dsdvlp/java/tmijar/firs7/configs/clientcommands.xml -Dcom.coexis.syn.clientconfiglocation=file://localhost//dsdvlp/java/tmijar/firs7/configs/fsbbtd_client.xml -XX:+PrintGCTimeStamps -XX:+PrintGCDetails
java_command: com.coexis.syn.mqmessaging.daemon.RunDaemon -p /dsdvlp/bin/5/lndsfsd_fsbbtd.properties start
Environment Variables:
JAVA_HOME=/dsdvlp/java/jvm/jdk150
CLASSPATH=.:/dsdvlp/java/jar/jconnect520.jar:/dsdvlp/java/jar/vbjapp340.jar:/dsdvlp/java/jar/vbjorb340.jar:/dsdvlp/java/jar/javax_jndi120.jar
PATH=/usr/local/etc:/usr/lang:/usr/openwin/bin:/usr/ucb:/bin:/usr/etc:/usr/local/5/bin:/dsdvlp/bin/5:/dsdvlp/bin/4:/home/app/sybase/5/bin:/home/app/sybase/5/localscripts:/home/app/sybase/5/sqr:/home/app/lang:/home/app/lang/SC2.0.1:/usr/ccs/bin:/usr/local/opt/Acrobat3/bin:/dsdvlp/bin:.
LD_LIBRARY_PATH=/dsdvlp/java/jvm/jdk1.5.0_03/jre/lib/sparc/server:/dsdvlp/java/jvm/jdk1.5.0_03/jre/lib/sparc:/dsdvlp/java/jvm/jdk1.5.0_03/jre/../lib/sparc:/usr/lib:/usr/openwin/lib:/usr/local/5/lib:/dsdvlp/lib/5:/dstest/lib/5:/home/app/sybase/5/lib:/dstest/cats/sun4/lib:/tmitest/Opus/opus/lib
SHELL=/bin/csh
DISPLAY=CLI00184.mfil.local:1.0
OS=5
--------------- S Y S T E M ---------------
OS: Solaris 8 2/02 s28s_u7wos_08a SPARC
Copyright 2002 Sun Microsystems, Inc. All Rights Reserved.
Assembled 18 December 2001
uname:SunOS 5.8 Generic_117350-20 sun4u (T1 libthread)
rlimit: STACK 8192k, CORE 9216k, NOFILE 4096, AS infinity
load average:2.24 2.67 2.68
CPU:total 4 has_v8, has_v9, has_vis1, has_vis2, is_ultra3
Memory: 8k page, physical 8388608k(166384k free)
vm_info: Java HotSpot(TM) Server VM (1.5.0_03-b07) for solaris-sparc, built on Apr 13 2005 03:31:26 by unknown with unknown Workshop:0x550The very first suggestion I have is to move your VM to a more recent update of 1.5.0.
It looks like you are crashing with 5.0u3, and I'm pretty sure 5.0u16 is available. You
don't want to waste your time chasing a bug that's already been fixed. -
URL class is not being garbage collected
I have created two instances of the URL class to specify a file location for each image. I use com.symantec.itools.javax.swing.icons.ImageIcon class to display images specified by each URL instance as icons inside a button. The setImageLocation method(URL location) of the ImageIcon class sets the location to be displayed by this icon. The following is the code snippets used to create the ImageIcon instances:
private URL greenIconURL;
private URL redIconURL;
com.symantec.itools.javax.swing.icons.ImageIcon green_icon = new com.symantec.itools.javax.swing.icons.ImageIcon();
com.symantec.itools.javax.swing.icons.ImageIcon red_icon = new com.symantec.itools.javax.swing.icons.ImageIcon();
try
greenIconURL = new java.net.URL
("file:./images/greenline.gif");
green_icon.setImageLocation(greenIconURL);
catch (java.net.MalformedURLException error) { }
try
redIconURL = new java.net.URL
("file:./images/redline.gif");
red_icon.setImageLocation(redIconURL);
catch (java.net.MalformedURLException error) { }
I am using JProbe 5.0.1 Memory to determine the loitering objects when I remove the button from the JInternalFrame. I am using Java 1.2.2_08 version. The JProbe Memory Leak Doctor indicates that each URL instance has a reference to an entry in a HashMap table. The reference graph from the root set has a reference to SoftCache to HashMap to HashMap$Entry. To make this URL instance eligible for garbage collection, JProbe Memory Leak Doctor indicates I must remove the entry from the HashMap. How do I get access to this HashMap to remove the entry? If this is a problem with the version of the JDK, please let me know. Thank you in advance for your assistance.<root>Statics
-->sun.misc.SoftCache->java.util.HashMap->java.util.Has
Map$Entry[]->java.util.HashMap$Entry->java.net.URL
I do not an instance of HashMap in my class.
Therefore, the HashMap is either created by URLclass
or the
com.symantec.itools.javax.swing.icons.ImageIcon
class.SoftCache seems to have a normal HashMap inside
it/* Hash table mapping keys to ValueCells */
private Map hash;but if that is the HashMap in JProbe
information then the URL would have to be a key in
the map - otherwise there'd be another object in the
chain of class SoftCache.ValueCell
are you certain that the java.net.URL's in that
hashmap are your ones?
out of curiosity - are you certain that the URL's are
the/a problem (are you getting an OutOfMemoryError?)
asjfThe button that contains the URL's is the only one on the JInternalFrame. The JProbe Memory Debugger displays the java.net package name, the URL class name, the count (2), and the Count Change (+2). When I remove the button from the JInternalFrame, the aforementioned numbers on the Instance Summary remain the same. The snapshot of the Java Heap reveals that the two instances of the URL class are still there. The Memory Leak Doctor shows the reference graph from the root set:
<root>Statics->SoftCache->HashMap->HashMap$Entry[]->HashMap$Entry->URL
When I right click on the arrow between HashMap$Entry[] and HashMap$Entry to remove the reference, I receive the message: "Congratulations this object can be garbage collected..." It appears like private instance of Map in SoftCache is holding a strong reference.
I am not getting an OutOfMemoryError exception. -
I can't seem to remove / unload the external swf files e.g when the carousel.swf (portfolio) is displayed and I press the about button the about content is overlapping the carousel (portfolio) . How can I remove / unload an external swf file from the main flash file and load a new swf file, while at the same time removing garbage collection from memory?
This is the error message(s) I am receiving: "TypeError: Error #2007: Parameter child must be non-null.
at flash.display::DisplayObjectContainer/removeChild()
at index_fla::MainTimeline/Down3()"
import nl.demonsters.debugger.MonsterDebugger;
var d:MonsterDebugger=new MonsterDebugger(this);
stage.scaleMode=StageScaleMode.NO_SCALE;
stage.align=StageAlign.TOP_LEFT;
stage.addEventListener(Event.RESIZE, resizeHandler);
// loader is the loader for portfolio page swf
var loader:Loader;
var loader2:Loader;
var loader3:Loader;
var loader1:Loader;
// resize content
function resizeHandler(event:Event):void {
// resizes portfolio page to center
loader.x = (stage.stageWidth - loader.width) * .5;
loader.y = (stage.stageHeight - loader.height) * .5;
// resizes about page to center
loader3.x = (stage.stageWidth - 482) * .5 - 260;
loader3.y = (stage.stageHeight - 492) * .5 - 140;
/*loader2.x = (stage.stageWidth - 658.65) * .5;
loader2.y = (stage.stageHeight - 551.45) * .5;*/
addEventListener(Event.ENTER_FRAME, onEnterFrame,false, 0, true);
function onEnterFrame(ev:Event):void {
var requesterb:URLRequest=new URLRequest("carouselLoader.swf");
loader = null;
loader = new Loader();
loader.name ="carousel1"
//adds gallery.swf to stage at begining of movie
loader.contentLoaderInfo.addEventListener(IOErrorEvent.IO_ERROR, ioError);
function ioError(event:IOErrorEvent):void {
trace(event);
try {
loader.load(requesterb);
} catch (error:SecurityError) {
trace(error);
addChild(loader);
loader.x = (stage.stageWidth - 739) * .5;
loader.y = (stage.stageHeight - 500) * .5;
// stop gallery.swf from duplication over and over again on enter frame
removeEventListener(Event.ENTER_FRAME, onEnterFrame);
//PORTFOLIO BUTTON
//adds eventlistner so that gallery.swf can be loaded
MovieClip(root).nav.portfolio.addEventListener(MouseEvent.MOUSE_DOWN, Down, false, 0, true);
function Down(event:MouseEvent):void {
// re adds listener for contact.swf and about.swf
MovieClip(root).nav.info.addEventListener(MouseEvent.MOUSE_DOWN, Down1, false, 0, true);
MovieClip(root).nav.about.addEventListener(MouseEvent.MOUSE_DOWN, Down3, false, 0, true);
//unloads gallery.swf from enter frame if users presses portfolio button in nav
var requester:URLRequest=new URLRequest("carouselLoader.swf");
loader = null;
loader = new Loader();
loader.name ="carousel"
loader.contentLoaderInfo.addEventListener(IOErrorEvent.IO_ERROR, ioError);
function ioError(event:IOErrorEvent):void {
trace(event);
try {
loader.load(requester);
} catch (error:SecurityError) {
trace(error);
addChild(loader);
loader.x = (stage.stageWidth - 739) * .5;
loader.y = (stage.stageHeight - 500) * .5;
removeChild( getChildByName("about") );
removeChild( getChildByName("carousel1") );
// remove eventlistner and prevents duplication of gallery.swf
MovieClip(root).nav.portfolio.removeEventListener(MouseEvent.MOUSE_DOWN, Down);
//INFORMATION BUTTON
//adds eventlistner so that info.swf can be loaded
MovieClip(root).nav.info.addEventListener(MouseEvent.MOUSE_DOWN, Down1, false, 0, true);
function Down1(event:MouseEvent):void {
//this re-adds the EventListener for portfolio so that end user can view again if they wish.
MovieClip(root).nav.portfolio.addEventListener(MouseEvent.MOUSE_DOWN, Down, false, 0, true);
MovieClip(root).nav.about.addEventListener(MouseEvent.MOUSE_DOWN, Down3, false, 0, true);
var requester:URLRequest=new URLRequest("contactLoader.swf");
loader2 = null;
loader2 = new Loader();
loader2.name ="contact"
loader2.contentLoaderInfo.addEventListener(IOErrorEvent.IO_ERROR, ioError);
function ioError(event:IOErrorEvent):void {
trace(event);
try {
loader2.load(requester);
} catch (error:SecurityError) {
trace(error);
addChild(loader2);
loader2.x = (stage.stageWidth - 658.65) * .5;
loader2.y = (stage.stageHeight - 551.45) * .5;
// remove eventlistner and prevents duplication of info.swf
MovieClip(root).nav.info.removeEventListener(MouseEvent.MOUSE_DOWN, Down1);
//ABOUT BUTTON
//adds eventlistner so that info.swf can be loaded
MovieClip(root).nav.about.addEventListener(MouseEvent.MOUSE_DOWN, Down3, false, 0, true);
function Down3(event:MouseEvent):void {
//this re-adds the EventListener for portfolio so that end user can view again if they wish.
MovieClip(root).nav.portfolio.addEventListener(MouseEvent.MOUSE_DOWN, Down, false, 0, true);
MovieClip(root).nav.info.addEventListener(MouseEvent.MOUSE_DOWN, Down1, false, 0, true);
var requester:URLRequest=new URLRequest("aboutLoader.swf");
loader3 = null;
loader3 = new Loader();
loader3.name ="about"
loader3.contentLoaderInfo.addEventListener(IOErrorEvent.IO_ERROR, ioError);
function ioError(event:IOErrorEvent):void {
trace(event);
try {
loader3.load(requester);
} catch (error:SecurityError) {
trace(error);
addChild(loader3);
loader3.x = (stage.stageWidth - 482) * .5 - 260;
loader3.y = (stage.stageHeight - 492) * .5 - 140;
removeChild( getChildByName("carousel") );
removeChild( getChildByName("carousel1") );
// remove eventlistner and prevents duplication of info.swf
MovieClip(root).nav.about.removeEventListener(MouseEvent.MOUSE_DOWN, Down3);
stop();Andrei1,
Thank you for the helpful advice. I made the changes as you suggested but I am receiving a #1009 error message even though my site is working the way I wan it to work. I would still like to fix the errors so that my site runs and error free. This is the error I am receiving:
"TypeError: Error #1009: Cannot access a property or method of a null object reference."
I'm sure this is not the best method to unload loaders and I am guessing this is why I am receiving the following error message.
loader.unload();
loader2.unload();
loader3.unload();
I also tried creating a function to unload the loader but received the same error message and my portfolio swf was not showing at all.
function killLoad():void{
try { loader.close(); loader2.close; loader3.close;} catch (e:*) {}
loader.unload(); loader2.unload(); loader3.unload();
I have a question regarding suggestion you made to set Mouse Event to "null". What does this do setting the MouseEvent do exactly? Also, since I've set the MouseEvent to null do I also have to set the loader to null? e.g.
---- Here is my updated code ----
// variable for external loaders
var loader:Loader;
var loader1:Loader;
var loader2:Loader;
var loader3:Loader;
// makes borders resize with browser size
function resizeHandler(event:Event):void {
// resizes portfolio page to center
loader.x = (stage.stageWidth - loader.width) * .5;
loader.y = (stage.stageHeight - loader.height) * .5;
// resizes about page to center
loader3.x = (stage.stageWidth - 482) * .5 - 260;
loader3.y = (stage.stageHeight - 492) * .5 - 140;
//adds gallery.swf to stage at begining of moviie
Down();
//PORTFOLIO BUTTON
//adds eventlistner so that gallery.swf can be loaded
MovieClip(root).nav.portfolio.addEventListener(MouseEvent.MOUSE_DOWN, Down, false, 0, true);
function Down(event:MouseEvent = null):void {
// re adds listener for contact.swf and about.swf
MovieClip(root).nav.info.addEventListener(MouseEvent.MOUSE_DOWN, Down1, false, 0, true);
MovieClip(root).nav.about.addEventListener(MouseEvent.MOUSE_DOWN, Down3, false, 0, true);
//unloads gallery.swf from enter frame if users presses portfolio button in nav
var requester:URLRequest=new URLRequest("carouselLoader.swf");
loader = new Loader();
loader.contentLoaderInfo.addEventListener(IOErrorEvent.IO_ERROR, ioError);
function ioError(event:IOErrorEvent):void {
trace(event);
try {
loader.load(requester);
} catch (error:SecurityError) {
trace(error);
this.addChild(loader);
loader.x = (stage.stageWidth - 739) * .5;
loader.y = (stage.stageHeight - 500) * .5;
// sure this is not the best way to do this - but it is unload external swfs
loader.unload();
loader2.unload();
loader3.unload();
// remove eventlistner and prevents duplication of gallery.swf
MovieClip(root).nav.portfolio.removeEventListener(MouseEvent.MOUSE_DOWN, Down);
//INFORMATION BUTTON
//adds eventlistner so that info.swf can be loaded
MovieClip(root).nav.info.addEventListener(MouseEvent.MOUSE_DOWN, Down1, false, 0, true);
function Down1(event:MouseEvent = null):void {
//this re-adds the EventListener for portfolio so that end user can view again if they wish.
MovieClip(root).nav.portfolio.addEventListener(MouseEvent.MOUSE_DOWN, Down, false, 0, true);
MovieClip(root).nav.about.addEventListener(MouseEvent.MOUSE_DOWN, Down3, false, 0, true);
var requester:URLRequest=new URLRequest("contactLoader.swf");
loader2 = null;
loader2 = new Loader();
loader2.contentLoaderInfo.addEventListener(IOErrorEvent.IO_ERROR, ioError);
function ioError(event:IOErrorEvent):void {
trace(event);
try {
loader2.load(requester);
} catch (error:SecurityError) {
trace(error);
addChild(loader2);
loader2.x = (stage.stageWidth - 658.65) * .5;
loader2.y = (stage.stageHeight - 551.45) * .5;
loader.unload();
loader2.unload();
loader3.unload();
// remove eventlistner and prevents duplication of info.swf
MovieClip(root).nav.info.removeEventListener(MouseEvent.MOUSE_DOWN, Down1);
//ABOUT BUTTON
//adds eventlistner so that info.swf can be loaded
MovieClip(root).nav.about.addEventListener(MouseEvent.MOUSE_DOWN, Down3, false, 0, true);
function Down3(event:MouseEvent = null):void {
//this re-adds the EventListener for portfolio so that end user can view again if they wish.
MovieClip(root).nav.portfolio.addEventListener(MouseEvent.MOUSE_DOWN, Down, false, 0, true);
MovieClip(root).nav.info.addEventListener(MouseEvent.MOUSE_DOWN, Down1, false, 0, true);
var requester:URLRequest=new URLRequest("aboutLoader.swf");
loader3 = null;
loader3 = new Loader();
loader3.contentLoaderInfo.addEventListener(IOErrorEvent.IO_ERROR, ioError);
function ioError(event:IOErrorEvent):void {
trace(event);
try {
loader3.load(requester);
} catch (error:SecurityError) {
trace(error);
addChild(loader3);
loader3.x = (stage.stageWidth - 482) * .5 - 260;
loader3.y = (stage.stageHeight - 492) * .5 - 140;
loader.unload();
loader2.unload();
loader3.unload();
// remove eventlistner and prevents duplication of info.swf
MovieClip(root).nav.about.removeEventListener(MouseEvent.MOUSE_DOWN, Down3);
stop(); -
Garbage collection of objects created inside a method
I have method and inside the method I create new Objects I mean I instantiate objects using new and call some methods on these objects.
once the method execution is completed and control goes to caller of the method will all the object created inside the method will be garbage collected ?
here with code
public List<StgAuditGeneral> getAudits(
List<StgAuditGeneral> audits= new ArrayList<StgAuditGeneral>();
for(Map<String, String> result :results ){
audits.add(new MapToObject<StgAuditGeneral>() {
@Override
public StgAuditGeneral getObject() {
StgAuditGeneral stg= new StgAuditGeneral();
return stg;
}.getObject());
}in the above method I cam creating tons of objects wil they be garbage collected immediatedly after jvm leaves the method ?user11138293 wrote:
I have method and inside the method I create new Objects I mean I instantiate objects using new and call some methods on these objects.
once the method execution is completed and control goes to caller of the method will all the object created inside the method will be garbage collected ?If there are no reachable references, to those objects, then when the method ends, they become eligible for GC. If and when they are actually collected is something we can't know or control, and generally don't care about. The only guarantee is that everything that can be collected will be collected before an OutOfMemoryError is thrown. So from our perspective, once it's eligible for collection, it is effectively collected.
If you pass references to those objects to something else that holds onto them after the method ends, then they are still reachable, and not eligible for collection.
However, you almost never need to even think about whether something is eligible for GC or not. It works pretty intuitively.
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