/*
 * $Header: /home/cvspublic/jakarta-commons/logging/src/java/org/apache/commons/logging/Log.java,v 1.14 2003/03/30 23:42:36 craigmcc Exp $
 * $Revision: 1.14 $
 * $Date: 2003/03/30 23:42:36 $
 *
 * ====================================================================
 *
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 1999-2003 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowlegement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
 *
 * 4. The names "The Jakarta Project", "Commons", and "Apache Software
 *    Foundation" must not be used to endorse or promote products derived
 *    from this software without prior written permission. For written
 *    permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache"
 *    nor may "Apache" appear in their names without prior written
 *    permission of the Apache Group.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 */


package org.apache.commons.logging;

/**
 * <p>A simple logging interface abstracting logging APIs.  In order to be
 * instantiated successfully by {@link LogFactory}, classes that implement
 * this interface must have a constructor that takes a single String
 * parameter representing the "name" of this Log.</p>
 *
 * <p> The six logging levels used by <code>Log</code> are (in order):
 * <ol>
 * <li>trace (the least serious)</li>
 * <li>debug</li>
 * <li>info</li>
 * <li>warn</li>
 * <li>error</li>
 * <li>fatal (the most serious)</li>
 * </ol>
 * The mapping of these log levels to the concepts used by the underlying
 * logging system is implementation dependent.
 * The implemention should ensure, though, that this ordering behaves
 * as expected.</p>
 *
 * <p>Performance is often a logging concern.
 * By examining the appropriate property,
 * a component can avoid expensive operations (producing information
 * to be logged).</p>
 *
 * <p> For example,
 * <code><pre>
 *    if (log.isDebugEnabled()) {
 *        ... do something expensive ...
 *        log.debug(theResult);
 *    }
 * </pre></code>
 * </p>
 *
 * <p>Configuration of the underlying logging system will generally be done
 * external to the Logging APIs, through whatever mechanism is supported by
 * that system.</p>
 *
 * @author <a href="mailto:sanders@apache.org">Scott Sanders</a>
 * @author Rod Waldhoff
 * @version $Id: Log.java,v 1.14 2003/03/30 23:42:36 craigmcc Exp $
 */
public interface Log {


    // ----------------------------------------------------- Logging Properties


    /**
     * <p> Is debug logging currently enabled? </p>
     *
     * <p> Call this method to prevent having to perform expensive operations
     * (for example, <code>String</code> concatination)
     * when the log level is more than debug. </p>
     */
    public boolean isDebugEnabled();


    /**
     * <p> Is error logging currently enabled? </p>
     *
     * <p> Call this method to prevent having to perform expensive operations
     * (for example, <code>String</code> concatination)
     * when the log level is more than error. </p>
     */
    public boolean isErrorEnabled();


    /**
     * <p> Is fatal logging currently enabled? </p>
     *
     * <p> Call this method to prevent having to perform expensive operations
     * (for example, <code>String</code> concatination)
     * when the log level is more than fatal. </p>
     */
    public boolean isFatalEnabled();


    /**
     * <p> Is info logging currently enabled? </p>
     *
     * <p> Call this method to prevent having to perform expensive operations
     * (for example, <code>String</code> concatination)
     * when the log level is more than info. </p>
     */
    public boolean isInfoEnabled();


    /**
     * <p> Is trace logging currently enabled? </p>
     *
     * <p> Call this method to prevent having to perform expensive operations
     * (for example, <code>String</code> concatination)
     * when the log level is more than trace. </p>
     */
    public boolean isTraceEnabled();


    /**
     * <p> Is warning logging currently enabled? </p>
     *
     * <p> Call this method to prevent having to perform expensive operations
     * (for example, <code>String</code> concatination)
     * when the log level is more than warning. </p>
     */
    public boolean isWarnEnabled();


    // -------------------------------------------------------- Logging Methods


    /**
     * <p> Log a message with trace log level. </p>
     *
     * @param message log this message
     */
    public void trace(Object message);


    /**
     * <p> Log an error with trace log level. </p>
     *
     * @param message log this message
     * @param t log this cause
     */
    public void trace(Object message, Throwable t);


    /**
     * <p> Log a message with debug log level. </p>
     *
     * @param message log this message
     */
    public void debug(Object message);


    /**
     * <p> Log an error with debug log level. </p>
     *
     * @param message log this message
     * @param t log this cause
     */
    public void debug(Object message, Throwable t);


    /**
     * <p> Log a message with info log level. </p>
     *
     * @param message log this message
     */
    public void info(Object message);


    /**
     * <p> Log an error with info log level. </p>
     *
     * @param message log this message
     * @param t log this cause
     */
    public void info(Object message, Throwable t);


    /**
     * <p> Log a message with warn log level. </p>
     *
     * @param message log this message
     */
    public void warn(Object message);


    /**
     * <p> Log an error with warn log level. </p>
     *
     * @param message log this message
     * @param t log this cause
     */
    public void warn(Object message, Throwable t);


    /**
     * <p> Log a message with error log level. </p>
     *
     * @param message log this message
     */
    public void error(Object message);


    /**
     * <p> Log an error with error log level. </p>
     *
     * @param message log this message
     * @param t log this cause
     */
    public void error(Object message, Throwable t);


    /**
     * <p> Log a message with fatal log level. </p>
     *
     * @param message log this message
     */
    public void fatal(Object message);


    /**
     * <p> Log an error with fatal log level. </p>
     *
     * @param message log this message
     * @param t log this cause
     */
    public void fatal(Object message, Throwable t);


}