[rules-dev] What You Should Know about Class Loaders

[Laird Nelson]

Hopefully not too off-topic here.  The most interesting thing I found from
BJ Hargrave's blog (
http://blog.bjhargrave.com/2007/09/classforname-caches-defined-class-in.html)
(thanks for linking to that) was a comment that basically refutes him.
 That comment quotes a Sun source:

*Applications should basically never call Classloader.loadClass(). It may
appear to work but it is often subtly wrong, can be a source of latent
bugs, and is almost never the best choice. They should instead call
Class.forName() using the 3 parameter version that takes a specific
Classloader instance.*
*
*
Anyway, I found that very interesting indeed; I now use
Class.forName("someName", true /* most times */,
Thread.currentThread().getContextClassLoader()).  Note that if for some
crazy reason the TCCL is null then the calling classloader will be used
instead.

Best,
Laird



On Wed, Apr 17, 2013 at 10:36 AM, Cristiano Gavião <cvgaviao at gmail.com>wrote:

> Well, I could find only a few places where the Class.forName() with the
> array parameter is needed.
> Probably the tip number 6 - Centralize would help with that.
>
>
> 2013/4/16 Mark Proctor <mproctor at codehaus.org>
>
>> Some things cause other problems:
>> *"Class.forName is Evil* - Class.forName will pin classes in memory
>> forever (almost, but long enough to cause problems). If you're forced to do
>> dynamic class loading use ClassLoader.loadClass instead. All variations of
>> the Class.forName suffer from the same problem. See BJ Hargrave's blog
>> about this<http://blog.bjhargrave.com/2007/09/classforname-caches-defined-class-in.html>
>> ."
>>
>> There is a bug in JDK which means that serialisation will not work with
>> String[] when using loadClass, and Class.forName must be used:
>> http://bugs.sun.com/view_bug.do?bug_id=6434149
>>
>> We hit this, and had to move all our stuff to Class.forName.
>>
>> Mark
>>
>> On 16 Apr 2013, at 18:51, Cristiano Gavião <cvgaviao at gmail.com> wrote:
>>
>> Would like to share this excellent article with Drools and JBPM
>> developers...
>>
>> http://blog.osgi.org/2011/05/what-you-should-know-about-class.html
>>
>> cheers,
>>
>> Cristiano
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>
>
>
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