[slf4j-user] log4j-over-slf4j checks circular dependency too strict

[Maarten Bosteels]

You meant components that use slf4j ?

Maarten

2010/8/10, Tom Liu <Tom.SH.Liu at morganstanley.com>:
> That's true. However, we have some customized components which uses
> commons-logging.
>
> On Tue, Aug 10, 2010 at 5:11 PM, Maarten Bosteels
> <mbosteels.dns at gmail.com> wrote:
>> Hi
>> You don't need slf4j at all to make tomcat 6 use log4j
>> See the tomcat docs.
>>
>> Maarten
>>
>> 2010/8/10, Tom Liu <Tom.SH.Liu at morganstanley.com>:
>>> Hi Ceki,
>>>
>>> I opened the bug here: http://bugzilla.slf4j.org/show_bug.cgi?id=194
>>>
>>> Thank you very much,
>>> Tom
>>>
>>> On Tue, Aug 10, 2010 at 3:09 PM, Ceki Gulcu <ceki at qos.ch> wrote:
>>>> Hi Tom,
>>>>
>>>> Sounds reasonable. Would you open a bug report requesting the change you
>>>> describe? Thanks,
>>>>
>>>> On 10.08.2010 06:38, Tom Liu wrote:
>>>>>
>>>>> Hi guys,
>>>>>
>>>>> I think log4j-over-slf4j (as well as jcl bridges) checks circular
>>>>> dependency too strict.
>>>>> Even when slf4j-log4j12.jar is visible, it does not necessarily mean
>>>>> it will be picked up by slf4j-api as the logging backend.
>>>>>
>>>>> Here is a setup in tomcat 6 demonstrate the issue:
>>>>> tomcat container lib contains: jcl-over-slf4j.jar, slf4j-api.jar,
>>>>> slf4j-log4j12.jar, log4j.jar
>>>>> Webapp WEB-INF/lib contains: log4j.jar, log4j-over-slf4j.jar,
>>>>> slf4j-api.jar, logback-core.jar, logback-access.jar.
>>>>> What we want to achieve is that tomcat logging (from commons-logging)
>>>>> will be routed to log4j and webapp's logging (from log4j) will be
>>>>> routed to logback.
>>>>> In theory, there will be no circular dependencies in runtime as
>>>>> logback is picked up as the logging backend. However, webapp failed to
>>>>> start because the "potential" circular dependency is detected.
>>>>>
>>>>> Is it possible to change the circular dependency detection algorithm
>>>>> to test against the actual binding picked up? I did a hack on
>>>>> org.apache.log4j.Log4jLoggerFactory which works for me:
>>>>> class Log4jLoggerFactory {
>>>>> ...
>>>>>
>>>>> static {
>>>>>
>>>>>         LoggerFactoryBinder binder = StaticLoggerBinder.getSingleton();
>>>>>         if
>>>>> ("org.slf4j.impl.Log4jLoggerFactory".equals(binder.getLoggerFactoryClassStr()))
>>>>> {
>>>>>             String part1 = "Detected both log4j-over-slf4j.jar AND
>>>>> slf4j-log4j12.jar on the class path, preempting StackOverflowError.
>>>>> REPLACED ";
>>>>>             String part2 = "See also " + LOG4J_DELEGATION_LOOP_URL + "
>>>>> for more details.";
>>>>>
>>>>>             Util.reportFailure(part1);
>>>>>             Util.reportFailure(part2);
>>>>>             throw new IllegalStateException(part1 + part2);
>>>>>         }
>>>>>
>>>>>     }
>>>>> ...
>>>>>
>>>>> }
>>>>>
>>>>> Thanks,
>>>>> Tom
>>>>
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