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https://issues.apache.org/jira/browse/LOG4J2-608?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14091980#comment-14091980
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Remko Popma commented on LOG4J2-608:
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About log levels, would it be an idea for the log4j JUL bridge to define custom
log4j2 log levels FINEST, FINER, FINE and CONFIG (intLevel TBD) to correspond
to the JUL levels? If we implement LOG4J2-589, these log levels can then be
used in log4j2 configuration to control filtering.
Different question: the description mentions the "easy case of setting the
{{java.util.logging.manager}} system property ahead of time to replace the
LogManager", and in addition a more difficult case to use reflection to
transfer "existing Loggers". I'm not sure that I understand the need to replace
existing Loggers. When would this be necessary?
Perhaps I am misunderstanding this, but I am worried that transferring from one
JUL logging implementation to another, while the application is running, would
be a lot of work and would be more fragile than a simple replace-at-startup
implementation. Would it not be enough to ask users to set the
{{java.util.logging.manager}} system property in advance if they want logging
to the JUL API to be redirected to the Logj2 implementation?
> Add support for a java.util.logging bridge.
> -------------------------------------------
>
> Key: LOG4J2-608
> URL: https://issues.apache.org/jira/browse/LOG4J2-608
> Project: Log4j 2
> Issue Type: New Feature
> Components: JDK 1.4 adapter
> Environment: OpenJDK 1.6, 1.7, 1.8, and any other JDK 1.6+
> implementations if possible
> Reporter: Matt Sicker
> Assignee: Matt Sicker
> Fix For: 2.1
>
> Attachments: 608-1.0.patch
>
>
> The JDK1.4 bridge from SLF4J is rather simplistic and looks error-prone
> (e.g., you need to manually start and stop the Handler). What I'd like is a
> Handler that includes Markers based on the log Level (which can be more than
> the built-in ones) along with a custom LogManager implementation.
> h2. The easy way
> For the easier use case of the user setting the {{java.util.logging.manager}}
> system property ahead of time to the correct LogManager implementation, this
> won't be too hard to support. I recommend extending the Logger class and
> having them log directly to their corresponding Log4j Logger instance. The
> custom LogManager should return these instances.
> For compatibility with existing Logger objects, the custom Handler class
> should be used to pass along log messages.
> h2. Reflection hackery
> Due to the lousy API that JDK1.4 gives you, there will need to be a bit of
> reflection hacking to inject itself into the LogManager and any existing
> Loggers. Because you can't replace a class instance via reflection, existing
> Logger references will have to use the Handler. The global LogManager can be
> replaced reflectively, but all its named Loggers should be transferred over
> to the new LogManager without losing any log messages during the process.
> After the LogManager is swapped out, any other calls to
> {{Logger.getLogger(String)}} or {{LogManager.getLogger(String)}} should
> return the Log4j implementations instead.
> h2. Questions
> h3. Level correspondence
> Which levels should the JUL levels correspond to? Here's my proposal:
> ||JUL Level Name||JUL Level Range||Corresponding Log4j Level||
> |ALL|{{Integer.MIN_VALUE}}|ALL|
> |FINEST|≤300|TRACE|
> |FINER|301 to 400|DEBUG|
> |FINE|401 to 500|DEBUG|
> |CONFIG|501 to 700|INFO|
> |INFO|701 to 800|INFO|
> |WARNING|801 to 900|WARN|
> |SEVERE|901 to 1000|ERROR|
> |?|>1000|FATAL|
> |OFF|{{Integer.MAX_VALUE}}|OFF|
> Along with those levels (which could also use the custom levels for
> non-standard ones), I'd also like to use markers here (if it makes sense).
> What I'm thinking is a parent marker named "java.util.logging", and then
> every JUL level (custom or standard) gets its own marker as well. This would
> be useful since JUL defines more levels than we have by default.
> h3. JUL config vs. Log4j config
> Should we override the JUL Loggers' levels based on the Log4j Loggers'
> levels? Or should we allow the JUL config to override the Log4j config?
> Should we allow JUL settings to be imported? Or should they be overridden by
> Log4j's configuration?
> h3. JDK compatibility
> What other JDKs are still out there for 1.6+ besides OpenJDK? The reflection
> hackery I have so far has fallbacks to try and find compatible methods or
> fields based on types, but who knows how different the JUL implementations
> could be? Plus, there could be licensing issues with alternative JDK code
> such that we can't effectively reverse engineer their implementations.
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