IsolatedLog4JLogger (Jetspeed-2 WebApp Logging 2.1.3 API)

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org.apache.jetspeed.webapp.logging
Class IsolatedLog4JLogger

java.lang.Object
  org.apache.jetspeed.webapp.logging.IsolatedLog4JLogger

All Implemented Interfaces:: org.apache.commons.logging.Log

public class IsolatedLog4JLogger
extends Object
implements org.apache.commons.logging.Log
extends Object
implements org.apache.commons.logging.Log

IsolatedLog4JLogger routes all commons-logging logging using Log4J to an ContextClassLoader specific Hierarchy.

For web or application servers providing (and enforcing) commons-logging and Log4J from a shared context (like JBoss), configuring Log4J loggers and appenders from within a (web) application overrides and resets the global Log4J LoggerRepository.

Capturing root logging for logging events from within the web application for example isn't possible using a Log4J propery or xml configuration without routing ALL root logging through the new (web application specific) configuration.

It is possible using the Log4J API directly instead of configuration files, but that requires hardcoded knowledge about how the logging is to be done.

Furthermore, if another application later on reconfigures the root logging again, the current root logging configuration is closed, detached and rerouted to the new configuration.

The same applies of course to common named loggers like capturing springframework logging.

The only way to prevent this stealing of logging configuration is allowing only one log4J configuration for the whole web or application server.
As this has to be done in a web or application server specific manner, setting up Jetspeed for different servers will become rather complex and difficult to automate.

The IsolatedLog4JLogger solves these problems by routing all logging through a statically configured ContextClassLoader isolated LoggerRepository.

Using this class requires a commons-logging.properties file in the WEB-INF/classes folder containing:

   org.apache.commons.logging.Log=org.apache.jetspeed.util.IsolatedLog4JLogger

During web application initialization, preferably from a ServletContextListener or a Servlet init method loaded with a load-on-startup value of 0 (zero), a new ContextClassLoader (e.g. web application) specific LoggerRepository as well as the initialization of Log4J should be configured as follows:

   Properties p = new Properties();
   p.load(new FileInputStream(log4jFile));
   // Create a new LoggerRepository
   Hierarchy h = new Hierarchy(new RootCategory(Level.INFO));
   // Configure the LoggerRepository with our own Log4J configuration
   new PropertyConfigurator().doConfigure(p,h);
   // set the LoggerRepository to be used for the current ContextClassLoader
   IsolatedLog4JLogger.setHierarchy(h);

Instead of using a PropertyConfigurator a DomConfigurator could be used likewise.

TODO: It might be useful to have this utility class available for usage by Portlet Applications too. Because this class must be included within a web application classpath, a separate jetspeed-tools or jetspeed-utils library will have to be created for it (and possibly other utility classes as well) which then can be put in the web application lib folder.

Version:: $Id: IsolatedLog4JLogger.java 531463 2007-04-23 13:35:58Z taylor $
Author:: Ate Douma

Field Summary
`private static org.apache.log4j.Hierarchy`	`hierarchy`
`private org.apache.commons.logging.impl.Log4JLogger`	`logger`
`private static HashMap`	`notIsolatedLoggers`

Constructor Summary
`IsolatedLog4JLogger(String name)`

Method Summary
`void`	`debug(Object arg0)`
`void`	`debug(Object arg0, Throwable arg1)`
`boolean`	`equals(Object obj)`
`void`	`error(Object arg0)`
`void`	`error(Object arg0, Throwable arg1)`
`void`	`fatal(Object arg0)`
`void`	`fatal(Object arg0, Throwable arg1)`
`private org.apache.commons.logging.impl.Log4JLogger`	`getLogger()`
`void`	`info(Object arg0)`
`void`	`info(Object arg0, Throwable arg1)`
`boolean`	`isDebugEnabled()`
`boolean`	`isErrorEnabled()`
`boolean`	`isFatalEnabled()`
`boolean`	`isInfoEnabled()`
`boolean`	`isTraceEnabled()`
`boolean`	`isWarnEnabled()`
`static void`	`setHierarchy(org.apache.log4j.Hierarchy hierarchy)`
`private void`	`setLogger(org.apache.commons.logging.impl.Log4JLogger logger)`
`String`	`toString()`
`void`	`trace(Object arg0)`
`void`	`trace(Object arg0, Throwable arg1)`
`void`	`warn(Object arg0)`
`void`	`warn(Object arg0, Throwable arg1)`

Methods inherited from class java.lang.Object
`clone, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait`

Field Detail

hierarchy

private static org.apache.log4j.Hierarchy hierarchy

notIsolatedLoggers

private static HashMap notIsolatedLoggers

logger

private org.apache.commons.logging.impl.Log4JLogger logger

Constructor Detail