How do I get java logging output to appear on a single line?

Like Obediah Stane said, it's necessary to create your own format method. But I would change a few things:

• Create a subclass directly derived from Formatter, not from SimpleFormatter. The SimpleFormatter has nothing to add anymore.

• Be careful with creating a new Date object! You should make sure to represent the date of the LogRecord. When creating a new Date with the default constructor, it will represent the date and time the Formatter processes the LogRecord, not the date that the LogRecord was created.

The following class can be used as formatter in a Handler, which in turn can be added to the Logger. Note that it ignores all class and method information available in the LogRecord.

import java.io.PrintWriter;
import java.io.StringWriter;
import java.util.Date;
import java.util.logging.Formatter;
import java.util.logging.LogRecord;

public final class LogFormatter extends Formatter {

    private static final String LINE_SEPARATOR = System.getProperty("line.separator");

    @Override
    public String format(LogRecord record) {
        StringBuilder sb = new StringBuilder();

        sb.append(new Date(record.getMillis()))
            .append(" ")
            .append(record.getLevel().getLocalizedName())
            .append(": ")
            .append(formatMessage(record))
            .append(LINE_SEPARATOR);

        if (record.getThrown() != null) {
            try {
                StringWriter sw = new StringWriter();
                PrintWriter pw = new PrintWriter(sw);
                record.getThrown().printStackTrace(pw);
                pw.close();
                sb.append(sw.toString());
            } catch (Exception ex) {
                // ignore
            }
        }

        return sb.toString();
    }
}

I've figured out a way that works. You can subclass SimpleFormatter and override the format method

    public String format(LogRecord record) {
        return new java.util.Date() + " " + record.getLevel() + " " + record.getMessage() + "\r\n";
    }

A bit surprised at this API I would have thought that more functionality/flexibility would have been provided out of the box

If you log in a web application using tomcat add:

-Djava.util.logging.ConsoleHandler.formatter = org.apache.juli.OneLineFormatter

On VM arguments

This logging is specific to your application and not a general Java feature. What application(s) are you running?

It might be that this is coming from a specific logging library that you are using within your own code. If so, please post the details of which one you are using.

if you're using java.util.logging, then there is a configuration file that is doing this to log contents (unless you're using programmatic configuration). So, your options are
1) run post -processor that removes the line breaks
2) change the log configuration AND remove the line breaks from it. Restart your application (server) and you should be good.