Use of Java Logging

Note: This program write a .Log file with all debugs


import java.util.logging.*;
import java.io.*;
public class TestLog {
public static Logger logger;
static {
try {
boolean append = true;
FileHandler fh = new FileHandler("TestLog.log", append);
//fh.setFormatter(new XMLFormatter());
fh.setFormatter(new SimpleFormatter());
logger = Logger.getLogger("TestLog");
logger.addHandler(fh);
}
catch (IOException e) {
e.printStackTrace();
}
}
public static void main(String args[]) {
logger.severe("my severe message");
logger.warning("my warning message");
logger.info("my info message");
}
}

OutPut

Nov 19, 2008 3:52:19 PM TestLog main
SEVERE: my severe message
Nov 19, 2008 3:52:19 PM TestLog main
WARNING: my warning message
Nov 19, 2008 3:52:19 PM TestLog main
INFO: my info message
------------------------------------------------------------------------------------------------------------------------------------
if the XMLFormatter is in use then the output is





2005-02-28T21:21:09
1109643669250
0
TestLog
SEVERE
TestLog
main
10
my severe message


2005-02-28T21:21:09
1109643669328
1
TestLog
WARNING
TestLog
main
10
my warning message


2005-02-28T21:21:09
1109643669328
2
TestLog
INFO
TestLog
main
10
my info message


------------------------------------------------------------------------------------------------------------------------------------
to customize the output, you can provide you own formatter

import java.util.logging.*;
import java.io.*;
public class TestLog {
public static Logger logger;
static {
try {
boolean append = true;
FileHandler fh = new FileHandler("TestLog.log", append);
fh.setFormatter(new Formatter() {
public String format(LogRecord rec) {
StringBuffer buf = new StringBuffer(1000);
buf.append(new java.util.Date());
buf.append(' ');
buf.append(rec.getLevel());
buf.append(' ');
buf.append(formatMessage(rec));
buf.append('\n');
return buf.toString();
}
});
logger = Logger.getLogger("TestLog");
logger.addHandler(fh);
}
catch (IOException e) {
e.printStackTrace();
}
}
public static void main(String args[]) {
logger.severe("my severe message");
logger.warning("my warning message");
logger.info("my info message");
}
}
then the output is
Mon Feb 28 21:30:54 EST 2005 SEVERE my severe message
Mon Feb 28 21:30:54 EST 2005 WARNING my warning message
Mon Feb 28 21:30:54 EST 2005 INFO my info message
------------------------------------------------------------------------------------------------------------------------------------
To limit the log file size and set a rolling pattern
int limit = 1000000; // 1 Mb
int numLogFiles = 3;
FileHandler fh = new FileHandler("TestLog%g.log", limit, numLogFiles);
------------------------------------------------------------------------------------------------------------------------------------
To suppress the logging output to the console

Logger rootLogger = Logger.getLogger("");
Handler[] handlers = rootLogger.getHandlers();
if (handlers[0] instanceof ConsoleHandler) {
rootLogger.removeHandler(handlers[0]);
}