Java log code example

Java log example

1. Logrecord filter

import java.util.logging.Filter;

import java.util.logging.Level;

import java.util.logging.LogRecord;

import java.util.logging.Logger;

 

public class SimpleFilter {

 

  private static Logger logger = Logger.getLogger("SimpleFilter");

 

  static class Duck {

  };

 

  static class Wombat {

  };

 

  static void sendLogMessages() {

    logger.log(Level.WARNING, "Aduck in the house!", new Duck());

    logger.log(Level.WARNING, "A Wombat at large!", newWombat());

  }

 

  public static void main(String[] args) {

    sendLogMessages();

    logger.setFilter(newFilter() {

      public boolean isLoggable(LogRecord record){

        Object[] params = record.getParameters();

        if (params == null)

          return true; // No parameters

        if (record.getParameters()[0]instanceof Duck)

          return true; // Only log Ducks

        return false;

      }

    });

    logger.info("After setting filter..");

    sendLogMessages();

 

  }

}

Output:

Aug 28,2013 11:46:04 AM SimpleFilter sendLogMessages

WARNING:A duck in the house!

Aug 28,2013 11:46:04 AM SimpleFilter sendLogMessages

WARNING:A Wombat at large!

Aug 28,2013 11:46:04 AM SimpleFilter main

INFO:After setting filter..

Aug 28,2013 11:46:04 AM SimpleFilter sendLogMessages

WARNING:A duck in the house!

注：重写isLoggable方法可以对logrecord对象进行过滤。

２．　Simple for Formatter Example

import java.util.logging.ConsoleHandler;

import java.util.logging.Formatter;

import java.util.logging.Handler;

import java.util.logging.LogRecord;

import java.util.logging.Logger;

 

public class SimpleFormatterExample {

 

  private static Logger logger = Logger.getLogger("SimpleFormatterExample");

 

  private static void logMessages() {

    logger.info("Line One");

    logger.info("Line Two");

  }

 

  public static void main(String[] args) {

    logger.setUseParentHandlers(false);

    Handler conHdlr = new ConsoleHandler();

    conHdlr.setFormatter(new Formatter() {

      public String format(LogRecord record) {

        return record.getLevel() + "  : "

            + record.getSourceClassName() + " -:- "

            + record.getSourceMethodName() + " -:- "

            + record.getMessage() + "\n";

      }

    });

    logger.addHandler(conHdlr);

    logMessages();

 

  }

}

Output:

INFO  : SimpleFormatterExample -:- logMessages -:- Line One

INFO  : SimpleFormatterExample -:- logMessages -:- Line Two

注：可以对输出的log格式进行特定格式化。

３．　Format log output by overriding tostring()function,

import java.util.logging.Level;

import java.util.logging.LogRecord;

 

public class PrintableLogRecord extends LogRecord {

 

  public PrintableLogRecord(Level level, String str) {

    super(level, str);

  }

 

  public StringtoString() {

    String result = "Level<" + getLevel() + ">\n" + "LoggerName<"

        + getLoggerName() + ">\n" + "Message<" + getMessage() + ">\n"

        + "CurrentMillis<" + getMillis() + ">\n" + "Params";

    Object[] objParams = getParameters();

    if (objParams == null)

      result += "<null>\n";

    else

      for (int i =0; i < objParams.length; i++)

        result += "  Param # <" + i + " value "

            + objParams[i].toString() + ">\n";

    result += "ResourceBundle<" + getResourceBundle()

        + ">\nResourceBundleName<" + getResourceBundleName()

        + ">\nSequenceNumber<" + getSequenceNumber()

        + ">\nSourceClassName<" + getSourceClassName()

        + ">\nSourceMethodName<" + getSourceMethodName()

        + ">\nThreadId<" + getThreadID() + ">\nThrown<" +getThrown()

        + ">";

    return result;

  }

 

  public static void main(String[] args) {

    PrintableLogRecord logRecord = new PrintableLogRecord(Level.FINEST,

        "SimpleLog Record");

    System.out.println(logRecord);

  }

}

Output:

Level<FINEST>

LoggerName<null>

Message<SimpleLog Record>

CurrentMillis<1377662640451>

Params<null>

ResourceBundle<null>

ResourceBundleName<null>

SequenceNumber<0>

SourceClassName<null>

SourceMethodName<null>

ThreadId<10>

Thrown<null>

 

4.  email log

import java.util.logging.*;
import java.io.*;
import java.util.Properties;
import javax.mail.*;
import javax.mail.internet.*;

public class EmailLogger {
  private static Logger logger = Logger.getLogger("EmailLogger");
  public static void main(String[] args) throws Exception {
    logger.setUseParentHandlers(false);
    Handler conHdlr = new ConsoleHandler();
    conHdlr.setFormatter(new Formatter() {
      public String format(LogRecord record) {
        return record.getLevel() + "  :  "
          + record.getSourceClassName() + ":"
          + record.getSourceMethodName() + ":"
          + record.getMessage() + "\n";
      }
    });
    logger.addHandler(conHdlr);
    logger.addHandler(
      new FileHandler("EmailLoggerOutput.xml"));
    logger.addHandler(new MailingHandler());
    logger.log(Level.INFO,
      "Testing Multiple Handlers", "SendMailTrue");
  }
}

// A handler that sends mail messages
class MailingHandler extends Handler {
  public void publish(LogRecord record) {
    Object[] params = record.getParameters();
    if(params == null) return;
    // Send mail only if the parameter is true
    if(params[0].equals("SendMailTrue")) {
      new MailInfo("bruce@theunixman.com",
        new String[] { "bruce@theunixman.com" },
        "smtp.theunixman.com", "Test Subject",
        "Test Content").sendMail();
    }
  }
  public void close() {}
  public void flush() {}
}

class MailInfo {
  private String fromAddr;
  private String[] toAddr;
  private String serverAddr;
  private String subject;
  private String message;
  public MailInfo(String from, String[] to,
    String server, String subject, String message) {
    fromAddr = from;
    toAddr = to;
    serverAddr = server;
    this.subject = subject;
    this.message = message;
  }
  public void sendMail() {
    try {
      Properties prop = new Properties();
      prop.put("mail.smtp.host", serverAddr);
      Session session =
        Session.getDefaultInstance(prop, null);
      session.setDebug(true);
      // Create a message
      Message mimeMsg = new MimeMessage(session);
      // Set the from and to address
      Address addressFrom = new InternetAddress(fromAddr);
      mimeMsg.setFrom(addressFrom);
      Address[] to = new InternetAddress[toAddr.length];
      for(int i = 0; i < toAddr.length; i++)
        to[i] = new InternetAddress(toAddr[i]);
      mimeMsg.setRecipients(Message.RecipientType.TO,to);
      mimeMsg.setSubject(subject);
      mimeMsg.setText(message);
      Transport.send(mimeMsg);
    } catch (Exception e) {
      throw new RuntimeException(e);
    }
  }
}