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A Java library for the Facebook Graph API
There is a newer version: 2.4.13
/*
 * Copyright 2007 Yusuke Yamamoto
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package facebook4j.internal.logging;

/**
 * @author Yusuke Yamamoto - yusuke at mac.com
 * @since Twitter4J 2.1.0
 */
public abstract class Logger {
    private static final LoggerFactory LOGGER_FACTORY;
    private static final String LOGGER_FACTORY_IMPLEMENTATION = "facebook4j.loggerFactory";

    static {
        LoggerFactory loggerFactory = null;
        //-Dfacebook4j.debug=true -Dfacebook4j.loggerFactory=facebook4j.internal.logging.StdOutLoggerFactory
        String loggerFactoryImpl = System.getProperty(LOGGER_FACTORY_IMPLEMENTATION);
        if (loggerFactoryImpl != null) {
            loggerFactory = getLoggerFactoryIfAvailable(loggerFactoryImpl, loggerFactoryImpl);
        }
        // use SLF4J if it's found in the classpath
        if (null == loggerFactory) {
            loggerFactory = getLoggerFactoryIfAvailable("org.slf4j.impl.StaticLoggerBinder", "facebook4j.internal.logging.SLF4JLoggerFactory");
        }
        // otherwise, use commons-logging if it's found in the classpath
        if (null == loggerFactory) {
            loggerFactory = getLoggerFactoryIfAvailable("org.apache.commons.logging.Log", "facebook4j.internal.logging.CommonsLoggingLoggerFactory");
        }
        // otherwise, use log4j if it's found in the classpath
        if (null == loggerFactory) {
            loggerFactory = getLoggerFactoryIfAvailable("org.apache.log4j.Logger", "facebook4j.internal.logging.Log4JLoggerFactory");
        }
        // on Google App Engine, use java.util.logging
        if (null == loggerFactory) {
            loggerFactory = getLoggerFactoryIfAvailable("com.google.appengine.api.urlfetch.URLFetchService", "facebook4j.internal.logging.JULLoggerFactory");
        }
        // otherwise, use the default logger
        if (null == loggerFactory) {
            loggerFactory = new StdOutLoggerFactory();
        }
        LOGGER_FACTORY = loggerFactory;
    }

    private static LoggerFactory getLoggerFactoryIfAvailable(String checkClassName, String implementationClass) {
        try {
            Class.forName(checkClassName);
            return (LoggerFactory) Class.forName(implementationClass).newInstance();
        } catch (ClassNotFoundException ignore) {
        } catch (InstantiationException e) {
            throw new AssertionError(e);
        } catch (SecurityException ignore) {
            // Unsigned applets are not allowed to access System properties
        } catch (IllegalAccessException e) {
            throw new AssertionError(e);
        }
        return null;
    }

    /**
     * Returns a Logger instance associated with the specified class.
     *
     * @param clazz class
     * @return logger instance
     */
    public static Logger getLogger(Class clazz) {
        return LOGGER_FACTORY.getLogger(clazz);
    }

    /**
     * tests if debug level logging is enabled
     *
     * @return if debug level logging is enabled
     */
    public abstract boolean isDebugEnabled();

    /**
     * tests if info level logging is enabled
     *
     * @return if info level logging is enabled
     */
    public abstract boolean isInfoEnabled();

    /**
     * tests if warn level logging is enabled
     *
     * @return if warn level logging is enabled
     */
    public abstract boolean isWarnEnabled();

    /**
     * tests if error level logging is enabled
     *
     * @return if error level logging is enabled
     */
    public abstract boolean isErrorEnabled();

    /**
     * @param message message
     */
    public abstract void debug(String message);

    /**
     * @param message  message
     * @param message2 message2
     */
    public abstract void debug(String message, String message2);

    /**
     * @param message message
     */
    public abstract void info(String message);

    /**
     * @param message  message
     * @param message2 message2
     */
    public abstract void info(String message, String message2);

    /**
     * @param message message
     */
    public abstract void warn(String message);

    /**
     * @param message  message
     * @param message2 message2
     */
    public abstract void warn(String message, String message2);

    /**
     * @param message message
     */
    public abstract void error(String message);

    /**
     * @param message message
     * @param th      throwable
     */
    public abstract void error(String message, Throwable th);

}