logging is the least of our problems if we get a "third" classloader.
e.g. which classloader should be used to load callback code ?
I would say TCL first *always*, but if the bytecode generated stuff
is placed in a third possibly completly seperated classloader calling
the callback can result in extremely weird errors - they will need to
have the same parent anyways to have compatible classes...hence TCL.
Or is there something I'm missing here ?
/max
It is popular to use static "log" field, this field is
shared by all contexts in shared deployment but first
loaded context will be used to configure logger or
"warn,indo,debug, ..." must be wrapped to cache and to
select "current configuration" using context loader on
every call (probably commons logging doe's it, but it
looks bit expensive for logging). So library must be
designed in very special way for this use case.
Probably there is no good common way and
parametrization or ClassLoader injection can help.
--- Max Rydahl Andersen <[EMAIL PROTECTED]>
wrote:
On Thu, 02 Feb 2006 22:00:39 +0100, Scott M Stark
<[EMAIL PROTECTED]>
wrote:
> Because the there may be serveral class loaders
associated with a
> deployment. I'm missing the exact context of this
discussion and how it
> correlates with the entity manager spi. Has there
been a definition of
> what the tcl must be for the entity manager spi
lifecycle? I don't see
> it browsing through the current ejb3 spec.
the problem is that if it is really necessary to
have a *third* external
classloader
which is neither available via someclass.forName nor
TCL then we need to
carry this classloader around and pass it on to hard
to reach places.
/max
>
> -----Original Message-----
> From: Max Andersen
> Sent: Thursday, February 02, 2006 3:09 PM
> To: Scott M Stark; Emmanuel Bernard; Bill Burke
> Cc: Hibernate development
> Subject: Re: [Hibernate] ClassLoader injection
>
> hi,
>
> Why is the tcl not the right one even when
generating classes ?
>
> if we don't use the same how can you have
consistent resource loading,
> annotation searching and code invocation ?
>
> /max
>
>> The general problem is that the thread context
class loader can be too
>> generic when you have a mesh of class loaders. As
is mentioned in
> latter
>> replies in this thread, if classes from a given
package namespace have
>> already been loaded via one class loader,
generally all subsequent
>> classes in the same package should be
loaded/defined using the same
>> class loader. Not doing so will lead to security
and type consistency
>> problems.
>>
>> In the case of the ejb3 entity manager spi, it
does make sense that
> you
>> would ask it for the correct class loader for
byte code manipulation
> vs
>> a class loader to query for resources and do
annotation searching.
>>
>> -----Original Message-----
>> From: Max Andersen
>> Sent: Tuesday, January 31, 2006 11:53 PM
>> To: Emmanuel Bernard; Bill Burke
>> Cc: Hibernate development; Scott M Stark
>> Subject: Re: [Hibernate] ClassLoader injection
>>
>> Hi,
>>
>> to bill, yes I know ctx current thread is the
only way, that was my
>> whole
>> point (using ctx current thread in
>> hibernate was actually the first patch i provided
to hibernate core ;)
>>
>> and yes, having a third classloader concept in
the spec sounds like a
>> very
>> broken thing.
>> I would love to hear why it is needed.
>>
>> /max
>>
>>> The RI team is going to creak, but I'm inclined
to remove it as well.
>>>
>>> AS for your first remark, what's wrong with
doing getResource with
> the
>>
>>> regular classloader? I don't get it.
>>>
>>>
>>> Bill Burke wrote:
>>>> I understand the need for
PUInfo.getNewTempClassLoader() as
>>>> getResource("META-INF/persistence.xml")
may/will return multiples.
>>>> Also, you may want to introspect the class for
annotations before
> you
>>
>>>> decide what needs to be bytecode massaged.
>>>>
>>>> As for getClassLoader()? I'm not sure of the
reasoning. I know
>> Scott
>>>> has some spec input on this. Maybe we should
get it removed?
>>>>
>>>> Emmanuel Bernard wrote:
>>>>> Year I'm aware of that Bill :-)
>>>>> But in this case, and like Max said, why on
earth the
>>>>> PersistenceUnitInfo has a getClassLoader()
method instead of using
>> the
>>>>> context CL?
>>>>>
>>>>>
>>>>> Bill Burke wrote:
>>>>>
>>>>>>
>>>>>>
>>>>>> Max Rydahl Andersen wrote:
>>>>>>
>>>>>>> If it is for the spec then I would argue
that the spec is very
>> wrong
>>>>>>> since it will
>>>>>>> break all other kind of stuff. Like how will
you convince all the
>>
>>>>>>> external libraries hibernate
>>>>>>> uses to use your "magic" classloader ? (e.g.
log4j, dom4j, cglib,
>>
>>>>>>> yada, yada)
>>>>>>>
>>>>>>
>>>>>> Thread.getContextCL() is the only way. If a
library doesn't use
>>>>>> Thread.getCCL() then it is a poorly written
library. App server
>> and
>>>>>> J2EE in general require this because of
classloader isolation
>> (scoped
>>>>>> ears or wars). If you are within Hibernate
code and call
>>>>>> Class.forName() it will use the classloader
that loaded Hibernate
>> to
>>>>>> load the class. (read the javadocs) and you
could get CCE, CNF
>>>>>> exceptions. If you already know this, then
apologies.
>>>>>>
>>>>>> The same issues effect the loading of
resources.
>>>>>>
>>>>>> Bill
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>
>>>
>>
>>
>>
>
>
>
--
--
Max Rydahl Andersen
callto://max.rydahl.andersen
Hibernate
[EMAIL PROTECTED]
http://hibernate.org
JBoss Inc
[EMAIL PROTECTED]
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Max Rydahl Andersen
callto://max.rydahl.andersen
Hibernate
[EMAIL PROTECTED]
http://hibernate.org
JBoss Inc
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