Re: [Springframework-developer] RE: CGLIB memory usage within class loader

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Jurgen,

That is why I have held fire on this for a while. In order for Spring to 
create a proxy of a class with no default constructor we need to pass 
the args and the arg types to Cglib. These need to come from somewhere. 
You can see how they are added to the Cglib proxy by looking at 
Cglib2AopProxy. I sm not too sure on how we should go about adding this 
to ProxyFactory and ProxyFactoryBean.

Rob

jürgen höller [werk3AT] wrote:

>Which arguments do you intend to pass in there, for creation of the CGLIB proxy? ProxyFactory usually works with an existing target object, so doesn't know about the constructor arguments used for creating the target object. 
> 
>Does this mean that the application developer would have to specify an arbitrary set of arguments that the target class will accept, just to get an instance of the CGLIB proxy subclass? That would feel a bit odd.
> 
>Juergen
> 
>
>________________________________
>
>Von: spr...@li... im Auftrag von Rob Harrop
>Gesendet: Mi 20.10.2004 00:18
>An: spr...@li...
>Betreff: Re: [Springframework-developer] RE: CGLIB memory usage within class loader
>
>
>
>Jurgen,
>
>The non-default constructor stuff works in the Cglib2AopProxy class but
>I need to modify ProxyFactory and ProxyFactoryBean to pass the new args
>across to Cglib2AopProxy.
>
>I'll hold fire on new commits until you add yours in.
>
>Rob
>
>jürgen höller [werk3AT] wrote:
>
>  
>
>>Rob,
>>
>>I haven't committed the changes yet, because I need to merge in your changes from the afternoon first :-) Will do so tomorrow morning. It would probably be good for you to wait until I've committed, to avoid any further merging conflicts...
>>
>>Your recent changes have to do with using non-default constructors on CGLIB proxies, as far as I see. Is this already fully working?
>>
>>Juergen
>>
>>
>>________________________________
>>
>>Von: spr...@li... im Auftrag von Rob Harrop
>>Gesendet: Di 19.10.2004 20:04
>>An: spr...@li...
>>Betreff: Re: [Springframework-developer] RE: CGLIB memory usage within class loader
>>
>>
>>
>>Jurgen/All,
>>
>>I'll check into this some more and see if I can reduce the memory usage
>>of the proxy classes. On another note I can't see the changes that
>>Jurgen has made, I made some changes about two hours ago and they seem
>>to have committed.
>>
>>Rob
>>
>>jürgen höller [werk3AT] wrote:
>>
>>
>>
>>    
>>
>>>BTW, I've polished Cglib2AopProxy's source code quite a bit: for example, it logs at debug level now (rather than info), and uses formatting consistent with the rest of Spring's sources.
>>>
>>>I've actually already done this polishing a second time: The earlier one got lost. It shows up in CVS, but then seems to have got overwritten by a subsequent commit. There was also a JDK 1.4 dependency fix in there (Boolean.valueOf with a boolean argument), which got lost too.
>>>
>>>So please, when you merge before a commit, double-check that you're not losing updates that someone else applied before you! It wasn't a big issue this time, but what if we don't notice it next time...
>>>
>>>Juergen
>>>
>>>
>>>-----Original Message-----
>>>From: jürgen höller [werk3AT]
>>>Sent: Tuesday, October 19, 2004 6:35 PM
>>>To: spr...@li...
>>>Subject: CGLIB memory usage within class loader
>>>
>>>
>>>I've just been made aware of the following by a werk3 colleague: When repeatedly creating CGLIB proxies for the same target class but for different advices - within the same class loader -, you'll create new proxied classes all the time, which won't get removed for the lifetime of the classes.
>>>
>>>The generated classes themselves are not the problem here. However, each of those proxy classes seems to hold strong references to its advices and target object, through holding the ProxyCallbackFilter instance that was passed into the Enhancer on proxy creation. Note that the proxy *class* holds that reference, not the proxy *instance*.
>>>
>>>The effect is that you can easily run out of memory if your advices or target objects occupy a large amount of memory, as none of those objects will get garbage collected as long as the CGLIB-generated proxy class is still hanging around in the class loader. This does *not* happen at all with JDK dynamic proxies.
>>>
>>>Of course, such excessive proxy creation is not the usual case in a production application. Web app restart is not a problem either, as the class loader will be shut down (releasing the CGLIB-generated proxy classes). The usual scenario where this memory leak becomes a problem is test suites, with application contexts getting created per test method.
>>>
>>>The following code snippet reproduces the issue:
>>>
>>>     while (true) {
>>>             ProxyFactory proxyFactory = new ProxyFactory();
>>>             proxyFactory.setTarget(new TestBean() {
>>>                     private byte[] field = new byte[1000000];
>>>             });
>>>             proxyFactory.addAdvice(new DebugInterceptor());
>>>             proxyFactory.setProxyTargetClass(true);
>>>             TestBean tb = (TestBean) proxyFactory.getProxy();
>>>             Thread.sleep(100);
>>>     }
>>>
>>>Depending on the max memory available to the VM, you'll run into an OutOfMemoryError sooner or later, as the target TestBean instance with its byte array of size 1000000 never gets garbage collected. Note that this does *not* happen when removing the addAdvice call, as we're just generating a single CGLIB proxy class then.
>>>
>>>Is this behavior unavoidable? What do we recommend for such testing scenarios then? In particular for integration tests with Hibernate, a 5 MB leak per context creation is not really acceptable. Of course it's preferable to share the application context as far as possible, but there are still valid use cases for repeated creation...
>>>
>>>Juergen
>>>
>>>
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