06 September 2007

Directing Log4j logs into OC4J logging system

My last posts have focussed on using the JDK standard logging API, and directing the logs being emitted into the OC4J logging system so they can be viewed and searched using the ASC LogViewer.

The log-handler mechanism we have works with the JDK standard logging constructs. The appender mechanism used by log4j is not covered by the basic configuration option in j2ee-config.xml.

However if you are using log4j, then on the surface it looks you are apparently SOL.

But if you want to get a little dirty, here's how you can also choose to redirect log4j logs into the OC4J log files.

In the OracleAS distribution, we ship a JAR file -- $ORACLE_HOME/diagnostics/lib/ojdl-log4j.jar -- that contains an OracleAppender class. Turns out, this class is a log4j appender that transforms log4j messages into the OJDL XML form.

To use this appender, simply configure it using your preferred log4j configuration mechanism. I'll use log4j.properties as an example:


In this configuration, the log4j messages will be directed into the $ORACLE_HOME/j2ee/home/log/oc4j/log.xml file -- which is the "Diagnostics" file read and displayed by LogViewer.

To make use of the OracleAppender, you have to ensure that you have the classes available to the application to use.

One approach it to include the libraries within the application itself -- with JEE5 applications, this is dead simple using the new <librar-directory> facility, with which you specify a directory within the EAR file to hold libaries, and then plunk the libraries into that directory. EasyPeasy!

Another approach to this is to create a shared-library containing the log4j library and the ojdl-log4j.library, and then import this into the application when it is being deployed so the libraries are available to the application.

If you have a Web application, just plunk the libraries into the WEB-INF/lib directory and go.

Something to keep in mind when you are using the ojdl-log4j library is that it has a dependency on the log4j library, so they have to both be accessible at the same classloader level.

Once you have it configured, then the one log.xml file will contain log entries from OC4J, as well as any logs from log4j.

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1 comment:

marzapower said...

Hi, I recently released a log4j meta-library, called "Loggable".
It will ease development time and reduce the common log4j overhead while defining your application architecture.

Please, check it out and let me know what you think about it:

Thank you!