Re: [Simple-support] classloaders, interfaces, and misc. issues

[Niall G. <gal...@ya...>]

Hi,

In relation to your comments:

1) Yes I am aware that the Class.forName is not going
to offer a suitable solution to the problem you
mention. At the same time there are issues with the
class loading strategies available. Ill make sure that
a better class loading strategy is used in the next
release.

2) Ya, this is true. I typically tend not to expose
default compontents in this way, however it may be a
good idea to allow extension.

3) Mmm.. I thought this was working, I am sure I have
a test case for it. Perhaps I have only supported
abstract classes? Certainly an addition that should be
there.

4) The Persister is fully thread safe and can be
shared without concerns, I will mention it in the
javadocs.  

Thank you for your feedback,
Niall

--- "A. Rothman" <ami...@am...> wrote:

> 
> Hi, and once again thanx for this great package!
> 
> I've come across a few issues when using the
> package:
> 
> 1. When using Simple's jar file in an extension
> directory while the 
> application is in the regular classpath, this
> results in a 
> ClassDefNotFoundException when attempting
> deserialization. When 
> researching the problem, I came across the article
> at 
>
http://www.javageeks.com/Papers/ClassForName/ClassForName.pdf
> (somewhat 
> old but still relevant) that explains the problem in
> detail and provides 
> two possible solutions. In a nutshell, calling
> Class.forName(name) in 
> DefaultStrategy uses the classloader that was used
> to load the library, 
> which is the ext classloader, which doesn't see the
> classpath. I've 
> tried replacing this call with both suggested
> alternatives, and they 
> both worked properly:
> 
> type = Class.forName(name, true, 
> Thread.currentThread().getContextClassLoader());
> 
> type = Class.forName(name, true,
> ClassLoader.getSystemClassLoader());
> 
> It sounds like the former is the better one, since
> it gives the caller 
> the ability to set a custom classloader as well, but
> I'm not sure if 
> there are other consequences of using one or the
> other. In any case, 
> both worked in my case and allowed deserialization
> to complete successfully.
> 
> 2. As a side note, if the DefaultStrategy were
> publicly extendable, 
> making such a fix locally (until it is integrated
> into the Simple 
> distribution) would be quite simple. However, with
> the existing 
> DefaultStrategy, the only way to do this is to copy
> the entire class 
> into a custom strategy with a single-line fix, or,
> as I did when testing 
> the solutions, change the original package and
> recompile it. I think 
> making DefaultStrategy easily extendable would be
> the best solution for 
> making such small tweaks to the default strategy.
> 
> 3. When attempting to serialize an interface or
> abstract class (as the 
> root element), and exception is thrown. However,
> making a simple wrapper 
> class with a single field holding this
> interface/abstract class works 
> correctly by serializing the "class" attribute for
> correct 
> deserialization of the original concrete class. It
> would be great if 
> this were fixed so it worked also on the top level
> class without 
> requiring this redundant wrapper. Note that this
> would also enable 
> deserializing an arbitrary object without knowing
> it's type in advance!
> 
> 4. The Persister class javadocs don't specify how it
> relates to thread 
> safety - it can be helpful to specify explicitly
> whether a single static 
> instance can be used from many threads, or each
> thread needs its own 
> Persister instance, etc.
> 
> Thanks again!
> 
> Amichai
> 
> >
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