    001/*
    002 * Copyright 2001-2004 The Apache Software Foundation.
    003 *
    004 * Licensed under the Apache License, Version 2.0 (the "License");
    005 * you may not use this file except in compliance with the License.
    006 * You may obtain a copy of the License at
    007 *
    008 *      http://www.apache.org/licenses/LICENSE-2.0
    009 *
    010 * Unless required by applicable law or agreed to in writing, software
    011 * distributed under the License is distributed on an "AS IS" BASIS,
    012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    013 * See the License for the specific language governing permissions and
    014 * limitations under the License.
    015 */
    016
    017package org.apache.commons.logging;
    018
    019/**
    020 * <p>A simple logging interface abstracting logging APIs.  In order to be
    021 * instantiated successfully by {@link LogFactory}, classes that implement
    022 * this interface must have a constructor that takes a single String
    023 * parameter representing the "name" of this Log.</p>
    024 *
    025 * <p> The six logging levels used by <code>Log</code> are (in order):
    026 * <ol>
    027 * <li>trace (the least serious)</li>
    028 * <li>debug</li>
    029 * <li>info</li>
    030 * <li>warn</li>
    031 * <li>error</li>
    032 * <li>fatal (the most serious)</li>
    033 * </ol>
    034 * The mapping of these log levels to the concepts used by the underlying
    035 * logging system is implementation dependent.
    036 * The implementation should ensure, though, that this ordering behaves
    037 * as expected.</p>
    038 *
    039 * <p>Performance is often a logging concern.
    040 * By examining the appropriate property,
    041 * a component can avoid expensive operations (producing information
    042 * to be logged).</p>
    043 *
    044 * <p> For example,
    045 * <code><pre>
    046 *    if (log.isDebugEnabled()) {
    047 *        ... do something expensive ...
    048 *        log.debug(theResult);
    049 *    }
    050 * </pre></code>
    051 * </p>
    052 *
    053 * <p>Configuration of the underlying logging system will generally be done
    054 * external to the Logging APIs, through whatever mechanism is supported by
    055 * that system.</p>
    056 *
    057 * <p style="color: #E40; font-weight: bold;">Please note that this interface is identical to that found in JCL 1.1.1.</p>
    058 *
    059 * @author <a href="mailto:sanders@apache.org">Scott Sanders</a>
    060 * @author Rod Waldhoff
    061 * @version $Id: Log.java,v 1.19 2004/06/06 21:16:04 rdonkin Exp $
    062 */
    063public interface Log {
    064
    065    // ----------------------------------------------------- Logging Properties
    066
    067    /**
    068     * <p> Is debug logging currently enabled? </p>
    069     *
    070     * <p> Call this method to prevent having to perform expensive operations
    071     * (for example, <code>String</code> concatenation)
    072     * when the log level is more than debug. </p>
    073     */
    074    public boolean isDebugEnabled();
    075
    076    /**
    077     * <p> Is error logging currently enabled? </p>
    078     *
    079     * <p> Call this method to prevent having to perform expensive operations
    080     * (for example, <code>String</code> concatenation)
    081     * when the log level is more than error. </p>
    082     */
    083    public boolean isErrorEnabled();
    084
    085    /**
    086     * <p> Is fatal logging currently enabled? </p>
    087     *
    088     * <p> Call this method to prevent having to perform expensive operations
    089     * (for example, <code>String</code> concatenation)
    090     * when the log level is more than fatal. </p>
    091     */
    092    public boolean isFatalEnabled();
    093
    094    /**
    095     * <p> Is info logging currently enabled? </p>
    096     *
    097     * <p> Call this method to prevent having to perform expensive operations
    098     * (for example, <code>String</code> concatenation)
    099     * when the log level is more than info. </p>
    100     *
    101     * @return true if info enabled, false otherwise
    102     */
    103    public boolean isInfoEnabled();
    104
    105    /**
    106     * <p> Is trace logging currently enabled? </p>
    107     *
    108     * <p> Call this method to prevent having to perform expensive operations
    109     * (for example, <code>String</code> concatenation)
    110     * when the log level is more than trace. </p>
    111     *
    112     * @return true if trace enabled, false otherwise
    113     */
    114    public boolean isTraceEnabled();
    115
    116    /**
    117     * <p> Is warn logging currently enabled? </p>
    118     *
    119     * <p> Call this method to prevent having to perform expensive operations
    120     * (for example, <code>String</code> concatenation)
    121     * when the log level is more than warn. </p>
    122     */
    123    public boolean isWarnEnabled();
    124
    125    // -------------------------------------------------------- Logging Methods
    126
    127    /**
    128     * <p> Log a message with trace log level. </p>
    129     *
    130     * @param message log this message
    131     */
    132    public void trace(Object message);
    133
    134    /**
    135     * <p> Log an error with trace log level. </p>
    136     *
    137     * @param message log this message
    138     * @param t log this cause
    139     */
    140    public void trace(Object message, Throwable t);
    141
    142    /**
    143     * <p> Log a message with debug log level. </p>
    144     *
    145     * @param message log this message
    146     */
    147    public void debug(Object message);
    148
    149    /**
    150     * <p> Log an error with debug log level. </p>
    151     *
    152     * @param message log this message
    153     * @param t log this cause
    154     */
    155    public void debug(Object message, Throwable t);
    156
    157    /**
    158     * <p> Log a message with info log level. </p>
    159     *
    160     * @param message log this message
    161     */
    162    public void info(Object message);
    163
    164    /**
    165     * <p> Log an error with info log level. </p>
    166     *
    167     * @param message log this message
    168     * @param t log this cause
    169     */
    170    public void info(Object message, Throwable t);
    171
    172    /**
    173     * <p> Log a message with warn log level. </p>
    174     *
    175     * @param message log this message
    176     */
    177    public void warn(Object message);
    178
    179    /**
    180     * <p> Log an error with warn log level. </p>
    181     *
    182     * @param message log this message
    183     * @param t log this cause
    184     */
    185    public void warn(Object message, Throwable t);
    186
    187    /**
    188     * <p> Log a message with error log level. </p>
    189     *
    190     * @param message log this message
    191     */
    192    public void error(Object message);
    193
    194    /**
    195     * <p> Log an error with error log level. </p>
    196     *
    197     * @param message log this message
    198     * @param t log this cause
    199     */
    200    public void error(Object message, Throwable t);
    201
    202    /**
    203     * <p> Log a message with fatal log level. </p>
    204     *
    205     * @param message log this message
    206     */
    207    public void fatal(Object message);
    208
    209    /**
    210     * <p> Log an error with fatal log level. </p>
    211     *
    212     * @param message log this message
    213     * @param t log this cause
    214     */
    215    public void fatal(Object message, Throwable t);
    216
    217}