I started using it to redirect all sysout and syserr to log files instead of catalina.out but its not thread safe as I started getting below exceptions. Solution was to patch the library and make LoggerAppenderImpl.appendAndLog and LoggerAppenderImpl.append methods synchronized for now as I am relying on assumption that we wont have too many system.out in third party libraries. java.lang.StringIndexOutOfBoundsException: String index out of range: 117 at java.lang.String. (String.java:212) at java.lang.StringBuilder.toString(StringBuilder.java:430) at uk.org.lidalia.sysoutslf4j.context.LoggerAppenderImpl.flushBuffer(LoggerAppenderImpl.java:62) at uk.org.lidalia.sysoutslf4j.context.LoggerAppenderImpl.appendAndLog(LoggerAppenderImpl.java:57) at uk.org.lidalia.sysoutslf4j.system.SLF4JPrintStreamDelegate.appendAndLog(SLF4JPrintStreamDelegate.java:76) at uk.org.lidalia.sysoutslf4j.system.SLF4JPrintStreamDelegate.delegatePrintln(SLF4JPrintStreamDelegate.java:...