Flushing streamhandlers during debugging using java.util.logging Autoflush

Question

I've been trying to look up this answer for a while on google and thought I'd just come here for the answer.

During production this setup works fine as it prints to both stdout and stderr which I separate and parse through for later use, but during development we want to see these logging actions be printed as they happen ie every log record. I think java refers to this as auto flushing. I cannot seem to find where I can change the buffer size for the stream handler objects that I have in order to fix this problem.

Some options I've though about are the following:

1. Print the log to stdout in the Formatter
2. Flush the handlers after every method call (Maybe with groovy annotations)
3. Enable the console handler during debugging

I am using java.util.logging to handling all logging done with my application, we are creating a root logger using the following code:

public Logger buildLogger()
{
    Logger log = Logger.getLogger("") //TODO update when JDK updatesLogger.getGlobal() is what we would like to use here
    log.setLevel(Level.WARNING)
    log.setUseParentHandlers(false); //Turn off any Parent Handlers
    Handler[] handlers = log.getHandlers();
    for(Handler handler : handlers) {
        log.removeHandler(handler);
    }
    log.addHandler(soh); //Add stdOut Handler
    log.addHandler(seh); //Add stdErr Handler
    return log;
}

Handlers are here

public StreamHandler buildsoh()
    {
        def soh = new StreamHandler(System.out, formatter)
        soh.setLevel(Level.ALL); //Default StdOut Setting
        return soh;
    }

    public StreamHandler buildseh()
    {
        def seh = new StreamHandler(System.err, formatter)
        seh.setLevel(Level.SEVERE); //Default StdErr Setting
        return seh;
    }

Formatter is here:

public class MyLogFormatter extends Formatter {
    @Override
    public String format(LogRecord record) {
        StringBuffer log = new StringBuffer()
        log.append("[${record.getLevel()}]")
        log.append(new Date(record.getMillis()).format("yyyy-MM-dd HH:mm:ss"))
        log.append(" ")
        log.append("[").append(record.getSourceClassName() ?: record.getLoggerName())
        log.append(" ")
        log.append(record.getSourceMethodName() ?: " - ").append("]")
        log.append(": ");
        log.append(record.getMessage());
        log.append(System.getProperty("line.separator"));
        return log.toString();
    }
}

Thank you very much!

Answer 1

If you want to flush every record you log, may be this can be useful (in java):

public StreamHandler buildseh() {
    final StreamHandler seh = new StreamHandler(System.err, formatter) {
        @Override
        public synchronized void publish(final LogRecord record) {
            super.publish(record);
            flush();
        }
    };
    seh.setLevel(Level.SEVERE); // Default StdErr Setting
    return seh;
}