log4j not printing the stacktrace for exceptions

Question

I am using log4j with tomcat. When I log exceptions in my JSPs, servlets:

private Logger _log = Logger.getLogger(this.getClass());
...
try{...} catch (Except         


        

Answer 1

Actually, it's probably due to a hotspot optimization: after a certain number of the same exception being thrown it stops printing out trace. This can be turned off with a VM arg, see:

From http://www.oracle.com/technetwork/java/javase/relnotes-139183.html :

The compiler in the server VM now provides correct stack backtraces for all "cold" built-in exceptions. For performance purposes, when such an exception is thrown a few times, the method may be recompiled. After recompilation, the compiler may choose a faster tactic using preallocated exceptions that do not provide a stack trace. To disable completely the use of preallocated exceptions, use this new flag: -XX:-OmitStackTraceInFastThrow.

More here:

http://jawspeak.com/2010/05/26/hotspot-caused-exceptions-to-lose-their-stack-traces-in-production-and-the-fix/