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Simple Log4j Configuration
Log4j
is a simple and flexible logging framework. In this tutorial you
will learn how to configure log4j for your applications.Let's
get started first download the latest version of log4j
( Download(http://logging.apache.org/log4j/1.2/download.html)
).
I am using log4j version 1.2.15. Add the log4j-1.2.15.jar to the
classpath.
Next you need to create an instance of Logger class. You can create
one using the Logger.getLogger(HelloWorld.class) method. It takes
one argument the fully qualified class name.
Now we need to configure log4j. The simple way to do that is using
BasicConfigurator. configure() method. This will log all the messages
on the console.
Now everything is ready you can log messages using any of the
print statements of the Logger class. In the following code I
use the debug() method to display the "HelloWorld!"
message
package
com.chennaisunday.helloworld;
import
org.apache.log4j.BasicConfigurator;
import
org.apache.log4j.Logger;
public
class HelloWorld {
static
final Logger logger = Logger.getLogger(HelloWorld.class);
public
static void main(String[] args) {
BasicConfigurator.configure();
logger.debug("Hello
World!");
}
}
The other methods available are info(), warn(), error() and fatal().
Each method represents a logger level namely DEBUG, INFO, WARN,
ERROR and FATAL.
The following example shows how to use these methods.
The
following example shows how to use these methods.
package
com.chennaisunday.helloworld;
import
org.apache.log4j.BasicConfigurator;
import
org.apache.log4j.Logger;
public
class HelloWorld {
static
final Logger logger = Logger.getLogger(HelloWorld.class);
public
static void main(String[] args) {
BasicConfigurator.configure();
logger.debug("Sample
debug message");
logger.info("Sample
info message");
logger.warn("Sample
warn message");
logger.error("Sample
error message");
logger.fatal("Sample
fatal message");
}
}
Here
is the
output of the above code.
[main]
DEBUG com.chennaisunday.helloworld.HelloWorld - Sample debug message
[main]
INFO com.chennaisunday.helloworld.HelloWorld
- Sample info message
[main]
WARN com.chennaisunday.helloworld.HelloWorld
- Sample warn message
[main]
ERROR com.chennaisunday.helloworld.HelloWorld
- Sample error message
[main]
FATAL com.chennaisunday.helloworld.HelloWorld
- Sample fatal message
The output contains the time elapsed from
the start of the program in milliseconds, the thread name, the
logger level, the class name and the log message.
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