Using Shared Libraries to configure Log4j

As I was mucking around with Log4j last week, it occurred to me that I could make use of the OC4J shared-library mechanism to inject the Log4J properties files into an an application when it was being deployed -- after all the properties file is just read from the classpath.

Even better, what this enables an administrator to do is to configure a set of shared-libraries that contain different log4j properties file, say enabling different log levels, and then choose between them when the application is deployed. Or additionally, make changes to in a post-deployment manner to switch between different logging settings.

OK, enough with the banal description, here's a few screen shots to show you what I'm dribbling on about here.

First off, lets assume you have a desire to capture and route your log4j entries into the OC4J log system using the OracleAppender as described here and you have a properties file that configures the appropriate settings and the log level you want to enable.

log4j.rootLogger=INFO,OJDL
log4j.appender.OJDL=oracle.core.ojdl.log4j.OracleAppender
log4j.appender.OJDL.LogDirectory=${oracle.j2ee.home}/log/oc4j
#log4j.appender.APP1.MaxSize=1000000
#log4j.appender.APP1.MaxSegmentSize=200000
#log4j.appender.APP1.Encoding=iso-8859-1
log4j.appender.OJDL.ComponentId=OracleProd

The first thing to do is to put the log4j.properties file into a JAR file, then deploy it as a shared-library to OC4J.





Once the shared-library has been published, you will see it available on the server shared-libraries page, ready to be imported. Note that in the below, I actually have two different log4j.config shared-libraries deployed.



Once the shared-library is deployed, it is then available to be imported by applications when they are deployed. By importing the log4j.info.config shared-library, the log4j.properties file is made accessible to the application and therefore used to to configure log4j for the application.

To import the shared-library during the deployment process, use the Configure Classloading button on the Deployment Tasks page.





By selecting the desired log4j.config shared-library, it will be made available to the application, and therefore dictate how the log4j log entries for the application are handled. In this specific case, the ROOT logger is set to the INFO level, and the OracleAppender is being employed to direct the log entries into the OC4J log system.

Ultimately the customized shared-library settings for the application are written into the orion-application.xml for the deployed application.



If at some point you wanted to change this application to use a lower log level such as DEBUG or TRACE then you can easily modify the import-shared-library statement to import the shared-library that has the relevant log4j.properties configuration file.

In summary, using the Oc4J shared-library mechanism and a consistent naming convention should enable you to have as many reusable log4j configurations as you need that can be applied to your applications.

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Listening to: Billy Bragg - A New England