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