log4j redirect stdout to DailyRollingFileAppender

Asked 2009-07-29T13:15:45.770

I have a java app that uses log4j.

Config:

log4j.rootLogger=info, file

log4j.appender.file=org.apache.log4j.DailyRollingFileAppender
log4j.appender.file.File=${user.home}/logs/app.log
log4j.appender.file.layout=org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern=%d [%t] %c %p %m%n

So all the log statements are correctly appended to the file, but i am losing stdout and stderr. How do i redirect exception stack traces and sysouts to the daily rolled file ?

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2 Answers

110

// I set up a ConsoleAppender in Log4J to format Stdout/Stderr
log4j.rootLogger=DEBUG, CONSOLE
log4j.appender.CONSOLE=org.apache.log4j.ConsoleAppender
log4j.appender.CONSOLE.layout=org.apache.log4j.PatternLayout
log4j.appender.CONSOLE.layout.ConversionPattern=[%t] %-5p %c - %m%n


// And I call this StdOutErrLog.tieSystemOutAndErrToLog() on startup

public class StdOutErrLog {

    private static final Logger logger = Logger.getLogger(StdOutErrLog.class);

    public static void tieSystemOutAndErrToLog() {
        System.setOut(createLoggingProxy(System.out));
        System.setErr(createLoggingProxy(System.err));
    }

    public static PrintStream createLoggingProxy(final PrintStream realPrintStream) {
        return new PrintStream(realPrintStream) {
            public void print(final String string) {
                realPrintStream.print(string);
                logger.info(string);
            }
        };
    }
}

answered 2009-09-02T20:51:48.663

In Skaffman code : To remove empty lines in log4j logs, just add "println" method to PrintStream of createLoggingProxy

public static PrintStream createLoggingProxy(final PrintStream realPrintStream) {
    return new PrintStream(realPrintStream) {
        public void print(final String string) {
            logger.warn(string);
        }
        public void println(final String string) {
            logger.warn(string);
        }
    };
}

answered 2012-09-11T12:39:24.150

log4j redirect stdout to DailyRollingFileAppender

2 Answers

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