JDKLogHandler.java

/*
 * aitools utilities
 * Copyright (C) 2006 Noel Bush
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.

 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */

package org.aitools.util;

import java.util.logging.Handler;

/**
 * This handler takes a log message sent to the JDK's logging system and sends it to log4j.
 * 
 * @author <a href="mailto:noel@aitools.org">Noel Bush</a>
 */
public class JDKLogHandler extends java.util.logging.Handler {

  private static void replaceHandlers(java.util.logging.Logger jdkLogger, JDKLogHandler handler) {
    java.util.logging.Handler[] handlers = jdkLogger.getHandlers();
    for (Handler handler2 : handlers) {
      jdkLogger.removeHandler(handler2);
    }
    jdkLogger.addHandler(handler);
  }

  /**
   * Removes any handlers attached to the JDK root logger, and adds an instance of this.
   */
  public static void setupInterception() {
    replaceHandlers(java.util.logging.Logger.getLogger(""), new JDKLogHandler());
  }

  /**
   * @see java.util.logging.Handler#close()
   */
  @Override
  public void close() throws SecurityException {
    // Nothing to do.
  }

  /**
   * @see java.util.logging.Handler#flush()
   */
  @Override
  public void flush() {
    // Nothing to do.
  }

  /**
   * @see java.util.logging.Handler#publish(java.util.logging.LogRecord)
   */
  @Override
  public void publish(java.util.logging.LogRecord record) {
    // Translate the level to log4j.
    java.util.logging.Level jdkLevel = record.getLevel();
    org.apache.log4j.Level log4jLevel;
    if (jdkLevel == java.util.logging.Level.SEVERE) {
      log4jLevel = org.apache.log4j.Level.ERROR;
    }
    else if (jdkLevel == java.util.logging.Level.WARNING) {
      log4jLevel = org.apache.log4j.Level.WARN;
    }
    else if (jdkLevel == java.util.logging.Level.INFO || jdkLevel == java.util.logging.Level.CONFIG) {
      log4jLevel = org.apache.log4j.Level.INFO;
    }
    else if (jdkLevel == java.util.logging.Level.FINE) {
      log4jLevel = org.apache.log4j.Level.DEBUG;
    }
    else if (jdkLevel == java.util.logging.Level.FINER || jdkLevel == java.util.logging.Level.FINEST) {
      log4jLevel = org.apache.log4j.Level.TRACE;
    }
    else {
      assert false : String.format("Unknown JDK logging level %s.", jdkLevel);
      return;
    }

    // Get the log4j logger.
    String loggerName = record.getLoggerName();
    org.apache.log4j.Logger log4jLogger = org.apache.log4j.Logger.getLogger(loggerName);

    org.apache.log4j.spi.LoggingEvent event = new org.apache.log4j.spi.LoggingEvent(record.getSourceClassName(),
        log4jLogger, record.getMillis(), log4jLevel, record.getMessage(), record.getThrown());
    event.getLocationInformation();

    // Call the logger's appenders on a new event created based on the JDK log record.
    log4jLogger.callAppenders(event);
  }
}