Using system environment variables in log4j xml configuration

Question

Is it possible to reference system environment variables (as opposed to Java system properties) in a log4j xml configuration file?

I'd like to be able to do something like:

<level value="${env.LOG_LEVEL}" /> 

and have it get that from the system environment variables, so I can avoid having to pass in so many things with -D parameters.

Answer 1

I tried to do that recently and couldn't get it to work. What I ended up doing is sending a variable at startup. So say you have an environment variable called $LOG_LEVEL:

<level value="${log_level}" /> 

and at startup...

java -Dlog_level=$LOG_LEVEL your_app 

Answer 2

This syntax is documented only in log4j 2.X so make sure you are using the correct version. It does not work on the 1.X versions.

    <Appenders>     <File name="file" fileName="${env:LOG_PATH}">         <PatternLayout>             <Pattern>%d %p %c{1.} [%t] %m %ex%n</Pattern>         </PatternLayout>     </File> </Appenders>