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Re: [Springframework-developer] CachedIntrospectionResults
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From: Claudio D'A. <cla...@ob...> - 2004-07-16 08:15:04
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Thank's Guillaume.
I'm studing about the WeakHashMap and I've seen that WeakHashMap build a
weak reference on the key (it's right??), when the key hasn't any reference
the entity is removed by map.
Spring use a class type to save the key. When the class object haven't any
reference? When the Classloader is shutdown?
Can you explain to me (or advise to me if exists an article or tutorial) about?
Thanks,
Claudio
At 10.05 15/07/2004 -0400, you wrote:
>As Juergen pointed out, if you find a static member hasn't been garbage
>collected, it just means its ClassLoader cannot be garbage collected yet,
>the static member is not necessarly at fault there. For an explanation of
>the current behavior, see below.
>
>For the solution, you can use a ServletContextListener to call
>java.beans.Introspector.flushCaches() when the ServletContext is detroy
>(which causes the ClassLoader to be thrown away).
>
>> if (results == null) {
>> // can throw BeansException
>> results = new CachedIntrospectionResults(clazz);
>> boolean cacheSafe = isCacheSafe(clazz);
>> if (logger.isDebugEnabled()) {
>> logger.debug("Class [" + clazz.getName()
>> + "] is " + (!cacheSafe ? "not " : "") + "cache-safe");
>> }
>> classCache.put(clazz, new WeakReference(results));
>> }
>Since Spring 1.0.2, the current code of this method is the following :
>
> if (results == null) {
> // can throw BeansException
> results = new CachedIntrospectionResults(clazz);
> boolean cacheSafe = isCacheSafe(clazz);
> if (logger.isDebugEnabled()) {
> logger.debug("Class [" + clazz.getName() + "] is " +
> (!cacheSafe ? "not " : "") + "cache-safe");
> }
> if (cacheSafe) {
> classCache.put(clazz, results);
> }
> else {
> classCache.put(clazz, new WeakReference(results));
> }
> }
>
>What the isCacheSafe(Class) method does is check if the clazz's
>ClassLoader is the
>same as CachedIntrospectionResults, or a parent of it. Because what
>prevent garbage
>collection of a ClassLoader A is if a class of a ClassLoader B that is not
>for garbage
>collection has a reference on a class (or instance) of the ClassLoader
>A. However, if
>A is a parent of B (or B == A), then A cannot be collected anyway. Which
>is why if clazz
>is considered "cacheSafe", no WeakReference is necessary, and in such case
>it improve
>performance. For example, if the class introspected is a JDK class, or a
>Spring class, its
>ClassLoader can never be collected before the CachedIntrospectionResults
>class.
>
>>I don't understand about memory leak, weark or soft referance but I've
>>see that CachedIntrospectionResults is referenced
>>by CachedIntrospectionResults.classCache and there are 2 instances
>>(org.springframework.context.support.ResourceBundleMessageSource and
>>org.springframework.web.servlet.DispatcherServlet)
>I don't know what causes the ClassLoader to be retained, but you cannot
>easily know what is the cause, just knowning that singletons instances are
>still in the JVM only proves that the ClassLoader has not been garbage
>collected. The problem is that something in a parent (or sibling)
>ClassLoader still has a reference on a Class of your webapp's
>ClassLoader. The trick is to find what is.
>
>Guillaume
>
>Claudio D'Angelo wrote:
>>I've deployed the minimal application (see the spring's sample). There
>>isn't Quarts, ibatis or hibernate. There is a controller with a test.jsp only.
>>
>>I don't understand about memory leak, weark or soft referance but I've
>>see that CachedIntrospectionResults is referenced
>>by CachedIntrospectionResults.classCache and there are 2 instances
>>(org.springframework.context.support.ResourceBundleMessageSource and
>>org.springframework.web.servlet.DispatcherServlet)
>>
>>
>>Where I can call the java.beans.Introspector.flushCaches()?
>>
>>Please help. After 20 redeploy Tomcat goes in OutOfMemory and ELS craches
>>
>>At 15.17 15/07/2004 +0200, you wrote:
>>>If this happens with Spring 1.0.2, it is typically caused by *other*
>>>code that causes a leak. The ClassLoader is then still around, also
>>>showing Spring classes like CachedIntrospectionResults. This is not
>>>Spring's fault: Spring classes just keep hanging around as a side effect.
>>>
>>>Try calling "java.beans.Introspector.flushCaches()" on application
>>>shutdown. This is a typical source of such leaks: The JavaBeans
>>>Introspector might still refer to application classes. This is not
>>>caused by Spring: It's rather other libraries that use the Introspector,
>>>for example Quartz.
>>>
>>>Juergen
>>>
>>>
>>>________________________________
>>>
>>>Von:
>>><mailto:spr...@li...>spr...@li...
>>>im Auftrag von Rod Johnson
>>>Gesendet: Do 15.07.2004 14:38
>>>An:
>>><mailto:spr...@li...>spr...@li...
>>>Betreff: Re: [Springframework-developer] CachedIntrospectionResults
>>>classCache leak
>>>
>>>
>>>
>>>Claudio
>>>
>>>What version of Spring is your analysis against?
>>>
>>>R
>>>
>>>----- Original Message -----
>>>From: "Claudio D'Angelo"
>>><mailto:cla...@ob...><cla...@ob...>
>>>To:
>>><mailto:spr...@li...><spr...@li...>
>>>Sent: Thursday, July 15, 2004 10:26 AM
>>>Subject: [Springframework-developer] CachedIntrospectionResults classCache
>>>leak
>>>
>>>
>>> > Hi,
>>> > I'm analyzing with OptimizeIt my web application:
>>> > when I redeploy the application I note that instances of
>>> > CachedIntrospectionResults still in memory and for any redeploy the
>>> > instances raise.
>>>
>>>
>>>
>>>
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>>
>>Grazie e buon lavoro
>>
>>----------
>>Claudio D'Angelo
>>Software Consultant
>>ObjectWay S.p.A.
>>Via G.A. Boltraffio 7
>>20159 Milano (MI)
>>http://www.objectway.it
>>
>>
>>--
>>La presente comunicazione potrebbe contenere informazioni riservate e/o
>>protette
>>da segreto professionale ed e' indirizzata esclusivamente ai destinatari
>>della
>>medesima qui indicati. Se avete ricevuto per errore la presente
>>comunicazione,
>>siete invitati a segnalarcelo, rispondendo a questo stesso indirizzo di
>>e-mail,
>>e a cancellare il presente messaggio dal Vostro sistema. E' strettamente
>>proibito
>>e potrebbe essere fonte di violazione di legge qualsiasi uso,
>>comunicazione, copia
>>o diffusione dei contenuti di questa comunicazione da parte di chi la abbia
>>ricevuta per errore o in violazione degli scopi della presente.
>>Il messaggio e' stato analizzato alla ricerca di virus o contenuti
>>pericolosi ed
>>e' risultato NON infetto.
Grazie e buon lavoro
----------
Claudio D'Angelo
Software Consultant
ObjectWay S.p.A.
Via G.A. Boltraffio 7
20159 Milano (MI)
http://www.objectway.it
--
La presente comunicazione potrebbe contenere informazioni riservate e/o
protette
da segreto professionale ed e' indirizzata esclusivamente ai destinatari della
medesima qui indicati. Se avete ricevuto per errore la presente comunicazione,
siete invitati a segnalarcelo, rispondendo a questo stesso indirizzo di
e-mail,
e a cancellare il presente messaggio dal Vostro sistema. E' strettamente
proibito
e potrebbe essere fonte di violazione di legge qualsiasi uso, comunicazione,
copia
o diffusione dei contenuti di questa comunicazione da parte di chi la abbia
ricevuta per errore o in violazione degli scopi della presente.
Il messaggio e' stato analizzato alla ricerca di virus o contenuti pericolosi
ed
e' risultato NON infetto.
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