Log4j2配置文件无法输出日志至控制台/文件问题咨询

Hey Pete, let's work through your two log4j2 problems one by one—they're both common configuration tweaks, so we'll get them sorted quickly!

Issue 1: No logs from Apache, SpringFramework, or Hibernate #

The most likely culprits here are either missing bridge dependencies (to connect those frameworks' logging APIs to log4j2) or missing Logger configurations for those packages in your log4j2.xml.

Step-by-step fixes: #

1. Verify bridge dependencies
   If you're using Maven/Gradle, make sure you've included the right bridge jars to route logs from those frameworks to log4j2:

   • For Commons Logging (used by many Apache projects): Add log4j-jcl
   • For SLF4J (used by Spring/Hibernate): Add log4j-slf4j-impl
     Also, exclude any conflicting logging implementations (like logback or commons-logging itself) from your dependencies to avoid conflicts.

2. Add Logger configurations for framework packages
   In your log4j2.xml, explicitly define Loggers for the root packages of these frameworks, and link them to both your Console and File appenders:

   <!-- Apache components -->
   <Logger name="org.apache" level="info" additivity="false">
       <AppenderRef ref="Console"/>
       <AppenderRef ref="MyFile"/> <!-- This should match your file appender's name -->
   </Logger>
   
   <!-- Spring Framework -->
   <Logger name="org.springframework" level="info" additivity="false">
       <AppenderRef ref="Console"/>
       <AppenderRef ref="MyFile"/>
   </Logger>
   
   <!-- Hibernate -->
   <Logger name="org.hibernate" level="info" additivity="false">
       <AppenderRef ref="Console"/>
       <AppenderRef ref="MyFile"/>
   </Logger>
   

   • Set level to a value that makes sense (e.g., debug if you need detailed logs, info for general runtime messages)
   • additivity="false" prevents these logs from being duplicated by the root Logger (if you have one configured)

3. Check your Root Logger
   If you prefer not to define individual Loggers for each framework, ensure your Root Logger includes both appenders and has a level that doesn't filter out framework logs:

   <Root level="info">
       <AppenderRef ref="Console"/>
       <AppenderRef ref="MyFile"/>
   </Root>
   

   Just note that this will apply the same level to all unconfigured packages, so adjust the level accordingly.

Issue 2: com.foo.bar logs only go to file, not console #

This almost always means your com.foo.bar Logger isn't linked to the Console appender. Let's fix that:

Quick fix: #

Update your existing com.foo.bar Logger configuration to explicitly reference both appenders:

<Logger name="com.foo.bar" level="debug" additivity="false"> <!-- Adjust level as needed -->
    <AppenderRef ref="Console"/>
    <AppenderRef ref="MyFile"/>
</Logger>

• If you had additivity="true" set, logs would pass through to the Root Logger—but only if the Root Logger includes the Console appender. Using additivity="false" gives you more control over exactly where these logs go.
• Double-check that your Console appender is properly defined (e.g., correct target and layout settings):

  <Appender name="Console" type="Console">
      <Layout type="PatternLayout" pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
  </Appender>
  

Final Checks #

• Confirm your log4j2.xml is in the correct classpath location (e.g., src/main/resources for Maven projects) so the app loads it on startup.
• Verify file write permissions for your mylog.log path—if the app can't write to it, logs might silently fail (though console logs shouldn't be affected by this).
• Test with a lower log level (like debug) temporarily to ensure logs aren't being filtered out due to overly strict level settings.

内容的提问来源于stack exchange，提问作者Pete Long