log4j截断堆栈跟踪

Question

I'm having a problem printing the stacktrace to my log file. Log4j.properties:

log4j.appender.file=org.apache.log4j.RollingFileAppender
log4j.appender.file.File=/var/log/app/application.log
log4j.appender.file.layout=org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss} %c{1} [%p] %m%n

log4j.rootLogger=warn, file
log4j.logger.com.app=info, file
log4j.additivity.com.app=false

when I log an exception like this in my class UserGuard.java:

} catch (Exception e) {
    log.error("Uncaught error", e);
    response.setEntity(new StringRepresentation(" "));
    response.setStatus(Status.SERVER_ERROR_INTERNAL);
}

This results in my application.log :

2011-12-28 07:30:03 UserGuard [ERROR] Uncaught error
java.lang.NullPointerException

No stack trace shown. This is really annoying. Thanks!

Tried with same pom.xml and same log4j.properties on another machine and works ok. Should I think that the problem is my java version?

Answer 1

Your stack traces are most likely getting truncated due to an optimization in Hotspot. The optimization only builds the identical stacktrace a limited number of times, and then future instances of the exception from the same exact place don't build it.

You can either turn off this optimization using the -XX:-OmitStackTraceInFastThrow flag, or go back to earlier logs to find the first instance of this exception occuring (it's logged once, then optimized away later).

See this related StackOverflow question , and this one , and this blog post over here .

Answer 2

log4j有一个增强功能： http ： //logging.apache.org/log4j/1.2/apidocs/org/apache/log4j/EnhancedPatternLayout.html