@Override
  public String format(final LogRecord record) {
    StringWriter sw = new StringWriter();
    PrintWriter pw = new PrintWriter(sw);

    pw.println();
    pw.print('[');
    pw.print(record.getLevel().getName());
    pw.print(' ');
    pw.print(dateFormat.format(new Date(record.getMillis())));
    String threadName = Thread.currentThread().getName();
    if (threadName != null) {
      pw.print(' ');
      pw.print(threadName);
    }
    pw.print(" tid=0x");
    pw.print(Long.toHexString(Thread.currentThread().getId()));
    pw.print("] ");
    pw.print("(msgTID=");
    pw.print(record.getThreadID());

    pw.print(" msgSN=");
    pw.print(record.getSequenceNumber());
    pw.print(") ");

    String msg = record.getMessage();
    if (msg != null) {
      try {
        LogWriterImpl.formatText(pw, msg, 40);
      } catch (RuntimeException e) {
        pw.println(msg);
        pw.println("Ignoring the following exception:");
        e.printStackTrace(pw);
      }
    } else {
      pw.println();
    }
    if (record.getThrown() != null) {
      record.getThrown().printStackTrace(pw);
    }
    pw.close();
    try {
      sw.close();
    } catch (IOException ignore) {
    }
    return sw.toString();
  }
Implementation of the standard JDK formatter that formats a message in GemFire's log format.
geode-core/src/main/java/org/apache/geode/internal/logging/GemFireFormatter.java