How to use java.util.logger in a web application?

Question

I'm trying to use a logger across a web application. I have added the FileHandler to write the log into file. Now, I need to use the same handler across other classes/servlets in the project, so that logs from all classes are written to same text file. How can I achieve this?

/***
 * Initialize a logger
 */
public static Logger logger;
static {
    try {
      FileHandler fh = new FileHandler("log.txt", true);
      fh.setFormatter(new SimpleFormatter());
      logger = Logger.getLogger(MyClass.class.getName());
      logger.addHandler(fh);
    }
    catch (IOException e) {
      e.printStackTrace();
    }
}

Do I need to initialize the logger and add handler in every class as in above code? Any other techniques?

Answer 1

I'd consider using a logging framework such as Log4J.

Using it would just boil down to configuring the appenders (e.g. FileAppender) and log levels in a central file (.xml or .properties) and in each class that needs to define a logger you'd just do Log l = LogFactory.getLog(clazz); (where clazz is the class you define the logger for).

You could make the logger public static and use it from other classes as well but I'd not recommend it, since you normally want to know which logger (i.e. which class that logger was defined for) generated a log entry.

Answer 2

You could use the logging.properties file to define your handlers globally for the whole application. In this file you can fine-tune your logging needs.

Look here or just google for logging.properties.

Example from the link above:

handlers = java.util.logging.ConsoleHandler, java.util.logging.FileHandler

java.util.logging.ConsoleHandler.level = INFO
java.util.logging.FileHandler.level = ALL

java.util.logging.ConsoleHandler.formatter = java.util.logging.SimpleFormatter

You can even setup different logging behavior for each of you web applications by placing the logging.properties in WEB-INF/classes of your web app.

Answer 3

package package_name;

import java.io.IOException;

import java.util.Properties;

import org.apache.log4j.Logger;

import org.apache.log4j.PropertyConfigurator;


public class Log {

public  Log() 
{
        Properties props = new Properties();
    try {
        props.load(getClass().getResourceAsStream("/log4j.properties"));
    } catch (IOException e) {
        e.printStackTrace();
    }
    PropertyConfigurator.configure(props);//PropertyConfigurator.configure("log4j.properties");
}

public  Logger getLogger(Object obj) 
{
    Logger logger = Logger.getLogger(Object.class);
    return logger;
}

}

then we have to maintain a log4j.properties file in one of our packages,and the file should be as follows,

log4j.properties

log4j.rootLogger=DEBUG, R,CA

log4j.appender.R = org.apache.log4j.DailyRollingFileAppender

log4j.appender.R.File = c:\\our project name+LOGSLIVE\\logs\\project short name.log

log4j.appender.R.Append = true

log4j.appender.R.DatePattern = '_'yyyy-MM-dd'.log'

log4j.appender.R.layout = org.apache.log4j.PatternLayout

#log4j.appender.R.layout.ConversionPattern = %d{yyyy-MM-dd HH:mm:ss} [%t] [%p] %m%n

log4j.appender.R.layout.ConversionPattern = %d{yyyy-MM-dd HH:mm:ss} %5p [%t] (%F:%L) -  %m%n


#Console Appender

log4j.appender.CA=org.apache.log4j.ConsoleAppender

log4j.appender.CA.layout=org.apache.log4j.PatternLayout

log4j.appender.CA.layout.ConversionPattern=%5p [%t] (%F:%L) -  %m%n