Logback: the reliable, generic, fast and flexible logging framework.
Copyright (C) 1999-2015, 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.
/**
 * Logback: the reliable, generic, fast and flexible logging framework.
 * Copyright (C) 1999-2015, 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 ch.qos.logback.core.status.StatusUtil;
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 LoggerFactory class with an actual instance of ILoggerFactory is performed using information returned by this class. 
Author:
Ceki Gülcü/**
 * 
 * The binding of {@link LoggerFactory} class with an actual instance of
 * {@link ILoggerFactory} is performed using information returned by this class.
 * 
 * @author 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.
/**
     * 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 = "1.7.16"; // !final

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

    
The unique instance of this class.
/**
     * 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.
/**
     * Package access for testing purposes.
     */
    static void reset() {
        SINGLETON = new StaticLoggerBinder();
        SINGLETON.init();
    }

    
Package access for testing purposes.
/**
     * 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);
            }
            // logback-292
            if (!StatusUtil.contextHasStatusListener(defaultLoggerContext)) {
                StatusPrinter.printInCaseOfErrorsOrWarnings(defaultLoggerContext);
            }
            contextSelectorBinder.init(defaultLoggerContext, KEY);
            initialized = true;
        } catch (Exception t) { // see LOGBACK-1159
            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.getClass().getName();
    }

}