You are viewing a plain text version of this content. The canonical link for it is here.
Posted to users@tomcat.apache.org by "M. Manna" <ma...@gmail.com> on 2018/08/29 18:09:55 UTC
Possible Discrepancy in ClassLoading order when running in Linux
Hello,
I am not sure if this is a bug or something specific to our implementation,
so wanted to share that with others. Please forgive my idiocy.
We took a verbose classloading on Windows and it loaded two classes from
two different locations.
1) *SomeUtils*.class from *com.my.package.name <http://com.my.package.name>*
- placed in WEB-INF/classes
2) *SomeOtherUtils*.class from *com.my.package.name
<http://com.my.package.name>* - placed in myjar.jar in WEB-INF/lib
In Windows, we can load the SomeUtils.class from the "classes" directory
(correct) and SomeOtherUtils.class from jar (in lib directory, also
correct). The class *SomeUtils *exist in *both **lib *and *classes*. but as
per documentation, webapp loader will load things from classes dir first,
and then lib. And it won't load the same class from *lib *if found in *classes
*first. And it also honours the contract "Child loader must not load same
class loaded by parent". So identical package name isn't a problem.
When we deployed in Linux, it didn't quite happen. We saw that "lib" was
always looked up first. We understand that SomeUtils.class duplicated in
both lib and classes is not a "Good" practice. But what we don't understand
is why webapp classloader isn't searching classes directory and finding it
first? Is there something fundamentally different when it comes to Linux
e.g. ordering/searching which is out of tomcat's control?
We don't have the verbose log from Linux yet, but meanwhile any info is
helpful.
Thanks,
Re: Possible Discrepancy in ClassLoading order when running in Linux
Posted by "M. Manna" <ma...@gmail.com>.
Please ignore my question.
Seems like someone decided to try out a "Special" classloader - didn't have
the information before.
Thanks for responding anyway.
Regards,
On Wed, 29 Aug 2018 at 20:20, M. Manna <ma...@gmail.com> wrote:
> Thanks mark. We aren’t using delegation, but even with delegation classes
> directory are looked up first in the order.
>
> Tomcat version 8.5.32.
>
> Thanks,
>
> On Wed, 29 Aug 2018 at 19:31, Mark Thomas <ma...@apache.org> wrote:
>
>> On 29/08/18 19:09, M. Manna wrote:
>> > Hello,
>> >
>> > I am not sure if this is a bug or something specific to our
>> implementation,
>> > so wanted to share that with others. Please forgive my idiocy.
>> >
>> > We took a verbose classloading on Windows and it loaded two classes from
>> > two different locations.
>> >
>> > 1) *SomeUtils*.class from *com.my.package.name <
>> http://com.my.package.name>*
>> > - placed in WEB-INF/classes
>> > 2) *SomeOtherUtils*.class from *com.my.package.name
>> > <http://com.my.package.name>* - placed in myjar.jar in WEB-INF/lib
>> >
>> > In Windows, we can load the SomeUtils.class from the "classes" directory
>> > (correct) and SomeOtherUtils.class from jar (in lib directory, also
>> > correct). The class *SomeUtils *exist in *both **lib *and *classes*.
>> but as
>> > per documentation, webapp loader will load things from classes dir
>> first,
>> > and then lib. And it won't load the same class from *lib *if found in
>> *classes
>> > *first. And it also honours the contract "Child loader must not load
>> same
>> > class loaded by parent". So identical package name isn't a problem.
>> >
>> > When we deployed in Linux, it didn't quite happen. We saw that "lib" was
>> > always looked up first. We understand that SomeUtils.class duplicated in
>> > both lib and classes is not a "Good" practice. But what we don't
>> understand
>> > is why webapp classloader isn't searching classes directory and finding
>> it
>> > first? Is there something fundamentally different when it comes to Linux
>> > e.g. ordering/searching which is out of tomcat's control?
>> >
>> > We don't have the verbose log from Linux yet, but meanwhile any info is
>> > helpful.
>>
>> Tomcat version?
>>
>> WEB-INF/classes should always be searched before WEB-INF/lib by default
>> but there are ways to configure the resources implementation to modify
>> the search order.
>>
>> Mark
>>
>>
>> ---------------------------------------------------------------------
>> To unsubscribe, e-mail: users-unsubscribe@tomcat.apache.org
>> For additional commands, e-mail: users-help@tomcat.apache.org
>>
>>
Re: Possible Discrepancy in ClassLoading order when running in Linux
Posted by "M. Manna" <ma...@gmail.com>.
Thanks mark. We aren’t using delegation, but even with delegation classes
directory are looked up first in the order.
Tomcat version 8.5.32.
Thanks,
On Wed, 29 Aug 2018 at 19:31, Mark Thomas <ma...@apache.org> wrote:
> On 29/08/18 19:09, M. Manna wrote:
> > Hello,
> >
> > I am not sure if this is a bug or something specific to our
> implementation,
> > so wanted to share that with others. Please forgive my idiocy.
> >
> > We took a verbose classloading on Windows and it loaded two classes from
> > two different locations.
> >
> > 1) *SomeUtils*.class from *com.my.package.name <
> http://com.my.package.name>*
> > - placed in WEB-INF/classes
> > 2) *SomeOtherUtils*.class from *com.my.package.name
> > <http://com.my.package.name>* - placed in myjar.jar in WEB-INF/lib
> >
> > In Windows, we can load the SomeUtils.class from the "classes" directory
> > (correct) and SomeOtherUtils.class from jar (in lib directory, also
> > correct). The class *SomeUtils *exist in *both **lib *and *classes*. but
> as
> > per documentation, webapp loader will load things from classes dir first,
> > and then lib. And it won't load the same class from *lib *if found in
> *classes
> > *first. And it also honours the contract "Child loader must not load same
> > class loaded by parent". So identical package name isn't a problem.
> >
> > When we deployed in Linux, it didn't quite happen. We saw that "lib" was
> > always looked up first. We understand that SomeUtils.class duplicated in
> > both lib and classes is not a "Good" practice. But what we don't
> understand
> > is why webapp classloader isn't searching classes directory and finding
> it
> > first? Is there something fundamentally different when it comes to Linux
> > e.g. ordering/searching which is out of tomcat's control?
> >
> > We don't have the verbose log from Linux yet, but meanwhile any info is
> > helpful.
>
> Tomcat version?
>
> WEB-INF/classes should always be searched before WEB-INF/lib by default
> but there are ways to configure the resources implementation to modify
> the search order.
>
> Mark
>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: users-unsubscribe@tomcat.apache.org
> For additional commands, e-mail: users-help@tomcat.apache.org
>
>
Re: Possible Discrepancy in ClassLoading order when running in Linux
Posted by Mark Thomas <ma...@apache.org>.
On 29/08/18 19:09, M. Manna wrote:
> Hello,
>
> I am not sure if this is a bug or something specific to our implementation,
> so wanted to share that with others. Please forgive my idiocy.
>
> We took a verbose classloading on Windows and it loaded two classes from
> two different locations.
>
> 1) *SomeUtils*.class from *com.my.package.name <http://com.my.package.name>*
> - placed in WEB-INF/classes
> 2) *SomeOtherUtils*.class from *com.my.package.name
> <http://com.my.package.name>* - placed in myjar.jar in WEB-INF/lib
>
> In Windows, we can load the SomeUtils.class from the "classes" directory
> (correct) and SomeOtherUtils.class from jar (in lib directory, also
> correct). The class *SomeUtils *exist in *both **lib *and *classes*. but as
> per documentation, webapp loader will load things from classes dir first,
> and then lib. And it won't load the same class from *lib *if found in *classes
> *first. And it also honours the contract "Child loader must not load same
> class loaded by parent". So identical package name isn't a problem.
>
> When we deployed in Linux, it didn't quite happen. We saw that "lib" was
> always looked up first. We understand that SomeUtils.class duplicated in
> both lib and classes is not a "Good" practice. But what we don't understand
> is why webapp classloader isn't searching classes directory and finding it
> first? Is there something fundamentally different when it comes to Linux
> e.g. ordering/searching which is out of tomcat's control?
>
> We don't have the verbose log from Linux yet, but meanwhile any info is
> helpful.
Tomcat version?
WEB-INF/classes should always be searched before WEB-INF/lib by default
but there are ways to configure the resources implementation to modify
the search order.
Mark
---------------------------------------------------------------------
To unsubscribe, e-mail: users-unsubscribe@tomcat.apache.org
For additional commands, e-mail: users-help@tomcat.apache.org