Java by API/java.util.logging/Logger

Logger: addHandler(Handler handler)

  
import java.io.IOException;
import java.util.logging.ConsoleHandler;
import java.util.logging.FileHandler;
import java.util.logging.Handler;
import java.util.logging.Logger;
import java.util.logging.XMLFormatter;
public class MainClass {
  public static void main(String args[]) {
    Logger logger = Logger.getLogger("my.log");
    Handler handler = null;
    try {
      handler = new FileHandler("messages.log");
    } catch (IOException e) {
      System.out.println("Could not create file. Using the console handler");
      handler = new ConsoleHandler();
    }
    logger.addHandler(handler);
    handler.setFormatter(new XMLFormatter());
    logger.info("Our first logging message");
    logger.severe("Something terrible happened");
  }
}

Logger: config(String msg)

  

import java.util.logging.Logger;
public class Main {
  public static void main(String[] args) {
    Logger log = Logger.getLogger("global");
    log.finest("A");
    log.finer("B");
    log.fine("C");
    log.config("D");
    log.info("E");
    log.warning("O");
    log.severe("A");
  }
}

Logger: exiting(String sourceClass, String sourceMethod, Object result)

  
import java.util.logging.Level;
import java.util.logging.Logger;
//package com.mycompany;
class MyClass {
  public boolean myMethod(int p1, Object p2) {
    Logger logger = Logger.getLogger("com.mycompany.MyClass");
    if (logger.isLoggable(Level.FINER)) {
      logger.entering(this.getClass().getName(), "myMethod", new Object[] { new Integer(p1), p2 });
    }
    System.out.println("Method body");
    boolean result = true;
    if (logger.isLoggable(Level.FINER)) {
      logger.exiting(this.getClass().getName(), "myMethod", new Boolean(result));
      logger.exiting(this.getClass().getName(), "myMethod");
    }
    return result;
  }
}

Logger: finer(String msg)

  

import java.util.logging.Logger;
public class Main {
  public static void main(String[] args) {
    Logger log = Logger.getLogger("global");
    log.finest("A");
    log.finer("B");
    log.fine("C");
    log.config("D");
    log.info("E");
    log.warning("O");
    log.severe("A");
  }
}

Logger: fine(String msg)

  

import java.util.logging.Logger;
public class Main {
  public static void main(String[] args) {
    Logger log = Logger.getLogger("global");
    log.finest("A");
    log.finer("B");
    log.fine("C");
    log.config("D");
    log.info("E");
    log.warning("O");
    log.severe("A");
  }
}

Logger: finest(String msg)

  

import java.util.logging.Logger;
public class Main {
  public static void main(String[] args) {
    Logger log = Logger.getLogger("global");
    log.finest("A");
    log.finer("B");
    log.fine("C");
    log.config("D");
    log.info("E");
    log.warning("O");
    log.severe("A");
  }
}

Logger: getAnonymousLogger()

  
import java.util.logging.Handler;
import java.util.logging.Level;
import java.util.logging.LogRecord;
import java.util.logging.Logger;
import java.util.logging.StreamHandler;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class Main {
  public static void main(String args[]) {
    Logger log = Logger.getAnonymousLogger();
    setLoggerhandler(log);
    log.finest(new Exception().toString());
  }
  public static void setLoggerhandler(Logger logger) {
    Handler handler = new ExceptionHandler();
    logger.addHandler(handler);
    logger.setLevel(Level.ALL);
  }
}
class ExceptionHandler extends StreamHandler {
  public void publish(LogRecord record) {
    String msg = record.getMessage();
    int exceptionIndex = msg.indexOf("Exception");
    if (exceptionIndex > -1) {
      Pattern pattern = Pattern.rupile("(.*Exception.*)");
      Matcher matcher = pattern.matcher(msg);
      if (matcher != null && matcher.find()) {
        String err = "EXCEPTION FOUND " + matcher.group(1);
        System.out.println(err);
      }
    }
  }
}

Logger: getLogger(String name)

  
import java.util.logging.Logger;
public class MainClass {
  public static void main(String[] args) {
    Logger logger = Logger.getLogger("DeviceLog");
    logger.info("<Device id=\"99\"/>");
  }
}

Logger: info(String msg)

       
import java.util.logging.Logger;
public class Main {
  private static Logger logger = Logger.getLogger("InfoLogging");
  public static void main(String[] args) {
    logger.info("Logging an INFO-level message");
  }
}

Logger: isLoggable(Level level)

  
import java.util.logging.Level;
import java.util.logging.Logger;
public class Main {
  public static void main(String[] argv) throws Exception {
    Logger logger = Logger.getLogger("com.mycompany.MyClass");
    // Check if the message will be logged
    if (logger.isLoggable(Level.FINEST)) {
      logger.finest("my finest message");
    }
  }
}

Logger: logp(Level level, String sourceClass, String sourceMethod, String msg)

  

import java.util.logging.Level;
import java.util.logging.Logger;
public class Main {
  private static Logger logger = Logger.getLogger("InfoLogging2");
  public static void main(String[] args) {
    logger.logp(Level.INFO, "InfoLogging2", "main", "Logging an INFO-level message");
  }
}

Logger: setFilter(Filter newFilter)

  

import java.util.logging.Filter;
import java.util.logging.Level;
import java.util.logging.LogRecord;
import java.util.logging.Logger;
public class Main {
  private static Logger logger = Logger.getLogger("SimpleFilter");
  static class A {
  };
  static class B {
  };
  static void sendLogMessages() {
    logger.log(Level.WARNING, "message 1!", new A());
    logger.log(Level.WARNING, "message 2!", new B());
  }
  public static void main(String[] args) {
    sendLogMessages();
    logger.setFilter(new Filter() {
      public boolean isLoggable(LogRecord record) {
        Object[] params = record.getParameters();
        if (params == null)
          return true;
        if (record.getParameters()[0] instanceof A)
          return true;
        return false;
      }
    });
    logger.info("After setting filter..");
    sendLogMessages();
  }
}

Logger: setUseParentHandlers(boolean useParentHandlers)

  
import java.util.logging.ConsoleHandler;
import java.util.logging.FileHandler;
import java.util.logging.Logger;
public class MainClass {
  private static Logger logger = Logger.getLogger("MultipleHandlers2");
  public static void main(String[] args) throws Exception {
    FileHandler logFile = new FileHandler("MultipleHandlers2.xml");
    logger.addHandler(logFile);
    logger.addHandler(new ConsoleHandler());
    logger.setUseParentHandlers(false);
    logger.warning("Output to multiple handlers");
  }
}

Logger: severe(String msg)

  
import java.util.logging.Logger;
public class MainClass {
  public static void main(String[] args) {
    Logger logger = Logger.getLogger("com.jexp.log");
    logger.severe("severe");
    logger.warning("warning");
    logger.info("info");
    logger.config("config");
    logger.fine("fine");
    logger.finer("finer");
    logger.finest("value ="+42);  
  }
}

Logger: warning(String msg)

  

import java.util.logging.Logger;
public class Main {
  public static void main(String[] args) {
    Logger log = Logger.getLogger("global");
    log.finest("A");
    log.finer("B");
    log.fine("C");
    log.config("D");
    log.info("E");
    log.warning("O");
    log.severe("A");
  }
}