org.apache.juli.logging.impl

Class SeparateLogbackSupport

java.lang.Object

org.apache.juli.logging.impl.SeparateLogbackSupport

public class SeparateLogbackSupport
extends Object

Helper class that the SLF4JDelegatingLog relies on for bootstrapping the separated Logback system when the time has come.

When an SLF4J implementation is detected at class initialization, no fancy bootstrapping occurs. The detected implementation will just be used. This behavior is compatible with version 1.0.x of the juli-to-slf4j library.

When no SLF4J implementation is available right from the start, its bootstrapping will automatically be triggered as soon as it is detected.

This deferred bootstrapping is made of three steps, during which all loggers and logging events creations are blocked.

1. The LoggerFactory is triggered, binds to the StaticLoggerBinder of the Logback that is accessible only by the Catalina class loader, which is a child class loader
2. All pre-bootstrap logging events are flushed to Logback appenders.
3. All pre-bootstrap loggers are swapped with their actual counterpart as obtained by the SLF4J API through the standard LoggerFactory.getLogger(String)

For the bootstrapping process to properly block loggers and logging events creations in multi-thraded environments, this implementation synchronizes globally on the SLF4JDelegatingLog.class, exactly as the facade SLF4JDelegatingLog instances do (and are supposed to do).

The automatic bootstrap-time detection runs a check once every log requests. The current thread context class loader is compared with the class loader that has loaded this SeparateLogbackSupport class. When they start being different, then we conclude that the Catalina classloader has been created. The Logback system is then initialized. As a reminder, here is the difference between those two loaders:

• System class loader: its classpath is defined by the $CLASSPATH environment variable that is built from scratch in catalina.sh startup script, with the help of setenv.sh, if any. The Jar files it contains should be in $CATALINA_HOME/bin or $CATALINA_BASE/bin.
• Catalina class loader: in most setups, this is the common class loader in Tomcat, with a classpath made of $CATALINA_HOME/lib and $CATALINA_BASE/lib. Very few setups diverge from this default configuration.

For more details about Tomcat class loaders, see the Class Loader section of the Tomcat documentation.

Since:

1.1.0

Author:

Benjamin Gandon

Constructor Summary

Constructors

Constructor and Description
SeparateLogbackSupport()

Method Summary

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

SeparateLogbackSupport

public SeparateLogbackSupport()