How to Use Log4j with WebLogic Logging Services

WebLogic logging services use an implementation based on the Java Logging APIs, by default. Using the LogMBean.isLog4jLoggingEnabled attribute, you can direct the logging services to use Log4j instead.

In the Administration Console, you can specify Log4j or keep the default Java Logging implementation.

Alternatively, you can configure Log4j logging through the LogMBean interface and by adding WebLogic-specific Log4j classes, WL_HOME/server/lib/wllog4j.jar, and the log4j.jar file to the server CLASSPATH. The recommended way to do this is to place the wllog4j.jar and log4j.jar files in the DOMAIN_NAME/lib directory; there, they will get added to the server CLASSPATH dynamically during server startup.

Note: WebLogic Server does not provide a Log4j version in its distribution.

When Log4j is enabled, you get a reference to the org.apache.log4j.Logger that the server is using from the weblogic.logging.log4j.Log4jLoggingHelper class.

With a Log4j Logger reference, you can attach you own custom appender to receive the server log events; for example, you might attach an appender that sends the server log events to Syslog or the Windows Event Viewer. Additionally, you can use the Logger reference to issue log requests to WebLogic logging services; this requires that the Log4j libraries be available to your deployed application.

If your application has no requirement to interact with WebLogic logging services, package the Log4j libraries in the application's LIB directory. The server logging will continue to use the default Java Logging implementation.

Enabling Log4j Logging

To specify logging to a Log4j Logger instead of the default Java Logging:

* When you start the Administration Server, include the following Java option in the weblogic.Server command:

-Dweblogic.log.Log4jLoggingEnabled=true

* After the Administration Server has started, use the Administration Console to specify the Log4j logging implementation. See "Specifying the Logging Implementation" in the Administration Console Online Help.
* Use the WLST to set the value of the Log4jLoggingEnabled property and re-start the server.


The WLST commands to enable logging to a Log4j Logger in the Administration Server:

#invoke WLST
C:\>java weblogic.WLST

#connect WLST to an Administration Server
wls:/offline> connect('username','password')

#navigate to the writable MBean configuration tree
wls:/mydomain/serverConfig> edit()
wls:/mydomain/edit> startEdit()

#set cmo to the server log config
wls:/mydomain/edit !> cd("Servers/myserver/Log/myserver")

#set log4j logging to true
wls:/mydomain/edit/Servers/myserver/Log/myserver !> cmo.setLog4jLoggingEnabled(true)

#save and activate the changes
wls:/mydomain/edit/Servers/myserver/Log/myserver !> save()
wls:/mydomain/edit/Servers/myserver/Log/myserver !> activate()


You can enable Log4j for the server Logger as well as the domain Logger, which resides only on the Administration Server. The domain Log4j Logger reference is provided by invoking the weblogic.logging.log4j.Log4jLoggingHelper.getLog4jDomainLogger() method.

Log4j Code Example

import org.apache.log4j.Logger;
import weblogic.logging.log4j.Log4jLoggingHelper;
import weblogic.logging.LoggerNotAvailableException;

/**
* This example shows how to use the Log4j server Logger.
*/

public class MyLog4jTest {
public void testWLSLog4j() {
try {
Logger logger = Log4jLoggingHelper.getLog4jServerLogger();
logger.addAppender(myAppender); // The Appender is configured using either the log4j props file or other custom mechanism.
logger.info("Test log message");
} catch(LoggerNotAvailableException lex) {
System.err.println("Unable to get a reference to the log4j Logger: "+
lex.getMessage())
}
}
}



You have programmatic access to the Log4j Logger and its appenders (handlers) and layouts (formatters) for configuration purposes.

Java Logging is the default for client and server-side logging; Log4j is available only for server-side and not client-side logging.