org.eclipse.virgo.medic.slf4japifragment/src/main/java/org/slf4j/impl/StaticLoggerBinder.java

/**
 * Logback: the reliable, generic, fast and flexible logging framework.
 * Copyright (C) 1999-2009, QOS.ch. All rights reserved.
 *
 * This program and the accompanying materials are dual-licensed under
 * either the terms of the Eclipse Public License v1.0 as published by
 * the Eclipse Foundation
 *
 *   or (per the licensee's choosing)
 *
 * under the terms of the GNU Lesser General Public License version 2.1
 * as published by the Free Software Foundation.
 */
package org.slf4j.impl;

import org.slf4j.ILoggerFactory;
import org.slf4j.LoggerFactory;
import org.slf4j.helpers.Util;
import org.slf4j.spi.LoggerFactoryBinder;

import ch.qos.logback.classic.LoggerContext;
import ch.qos.logback.classic.util.ContextInitializer;
import ch.qos.logback.classic.util.ContextSelectorStaticBinder;
import ch.qos.logback.core.CoreConstants;
import ch.qos.logback.core.joran.spi.JoranException;
import ch.qos.logback.core.util.StatusPrinter;

/**
 * 
 * The binding of {@link LoggerFactory} class with an actual instance of
 * {@link ILoggerFactory} is performed using information returned by this class.
 * 
 * @author <a href="http://www.qos.ch/shop/products/log4jManual">Ceki
 *         G&uuml;lc&uuml;</a>
 */
public class StaticLoggerBinder implements LoggerFactoryBinder {

  /**
   * Declare the version of the SLF4J API this implementation is compiled
   * against. The value of this field is usually modified with each release.
   */
  // to avoid constant folding by the compiler, this field must *not* be final
  public static String REQUESTED_API_VERSION = "1.6"; // !final

  final static String NULL_CS_URL = CoreConstants.CODES_URL + "#null_CS";

  /**
   * The unique instance of this class.
   */
  private static StaticLoggerBinder SINGLETON = new StaticLoggerBinder();

  private static Object KEY = new Object();

  static {
    SINGLETON.init();
  }

  private boolean initialized = false;
  private LoggerContext defaultLoggerContext = new LoggerContext();
  private final ContextSelectorStaticBinder contextSelectorBinder = ContextSelectorStaticBinder
      .getSingleton();

  private StaticLoggerBinder() {
    defaultLoggerContext.setName(CoreConstants.DEFAULT_CONTEXT_NAME);
  }

  public static StaticLoggerBinder getSingleton() {
    return SINGLETON;
  }

  /**
   * Package access for testing purposes.
   */
  static void reset() {
    SINGLETON = new StaticLoggerBinder();
    SINGLETON.init();
  }

  /**
   * Package access for testing purposes.
   */
  void init() {
    try {
      try {
        new ContextInitializer(defaultLoggerContext).autoConfig();
      } catch (JoranException je) {
        Util.report("Failed to auto configure default logger context", je);
      }
      StatusPrinter.printInCaseOfErrorsOrWarnings(defaultLoggerContext);
      contextSelectorBinder.init(defaultLoggerContext, KEY);
      initialized = true;
    } catch (Throwable t) {
      // we should never get here
      Util.report("Failed to instantiate [" + LoggerContext.class.getName()
          + "]", t);
    }
  }

  public ILoggerFactory getLoggerFactory() {
    if (!initialized) {
      return defaultLoggerContext;
    }

    if (contextSelectorBinder.getContextSelector() == null) {
      throw new IllegalStateException(
          "contextSelector cannot be null. See also " + NULL_CS_URL);
    }
    return contextSelectorBinder.getContextSelector().getLoggerContext();
  }

  public String getLoggerFactoryClassStr() {
    return contextSelectorBinder.getContextSelector().getClass().getName();
  }

}