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    1   /*
    2    * Licensed to the Apache Software Foundation (ASF) under one or more
    3    * contributor license agreements.  See the NOTICE file distributed with
    4    * this work for additional information regarding copyright ownership.
    5    * The ASF licenses this file to You under the Apache License, Version 2.0
    6    * (the "License"); you may not use this file except in compliance with
    7    * the License.  You may obtain a copy of the License at
    8    *
    9    *      http://www.apache.org/licenses/LICENSE-2.0
    10   *
    11   * Unless required by applicable law or agreed to in writing, software
    12   * distributed under the License is distributed on an "AS IS" BASIS,
    13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    14   * See the License for the specific language governing permissions and
    15   * limitations under the License.
    16   */
    17
    18
    19  package org.apache.commons.logging;
    20
    21  /**
    22   * <p>A simple logging interface abstracting logging APIs.  In order to be
    23   * instantiated successfully by {@link LogFactory}, classes that implement
    24   * this interface must have a constructor that takes a single String
    25   * parameter representing the "name" of this Log.</p>
    26   *
    27   * <p> The six logging levels used by <code>Log</code> are (in order):
    28   * <ol>
    29   * <li>trace (the least serious)</li>
    30   * <li>debug</li>
    31   * <li>info</li>
    32   * <li>warn</li>
    33   * <li>error</li>
    34   * <li>fatal (the most serious)</li>
    35   * </ol>
    36   * The mapping of these log levels to the concepts used by the underlying
    37   * logging system is implementation dependent.
    38   * The implemention should ensure, though, that this ordering behaves
    39   * as expected.</p>
    40   *
    41   * <p>Performance is often a logging concern.
    42   * By examining the appropriate property,
    43   * a component can avoid expensive operations (producing information
    44   * to be logged).</p>
    45   *
    46   * <p> For example,
    47   * <code><pre>
    48   *    if (log.isDebugEnabled()) {
    49   *        ... do something expensive ...
    50   *        log.debug(theResult);
    51   *    }
    52   * </pre></code>
    53   * </p>
    54   *
    55   * <p>Configuration of the underlying logging system will generally be done
    56   * external to the Logging APIs, through whatever mechanism is supported by
    57   * that system.</p>
    58   *
    59   * @author <a href="mailto:sanders@apache.org">Scott Sanders</a>
    60   * @author Rod Waldhoff
    61   * @version $Id: Log.java 424107 2006-07-20 23:15:42Z skitching $
    62   */
    63  public interface Log {
    64
    65
    66      // ----------------------------------------------------- Logging Properties
    67
    68
    69      /**
    70       * <p> Is debug logging currently enabled? </p>
    71       *
    72       * <p> Call this method to prevent having to perform expensive operations
    73       * (for example, <code>String</code> concatenation)
    74       * when the log level is more than debug. </p>
    75       *
    76       * @return true if debug is enabled in the underlying logger.
    77       */
    78      public boolean isDebugEnabled();
    79
    80
    81      /**
    82       * <p> Is error logging currently enabled? </p>
    83       *
    84       * <p> Call this method to prevent having to perform expensive operations
    85       * (for example, <code>String</code> concatenation)
    86       * when the log level is more than error. </p>
    87       *
    88       * @return true if error is enabled in the underlying logger.
    89       */
    90      public boolean isErrorEnabled();
    91
    92
    93      /**
    94       * <p> Is fatal logging currently enabled? </p>
    95       *
    96       * <p> Call this method to prevent having to perform expensive operations
    97       * (for example, <code>String</code> concatenation)
    98       * when the log level is more than fatal. </p>
    99       *
    100      * @return true if fatal is enabled in the underlying logger.
    101      */
    102     public boolean isFatalEnabled();
    103
    104
    105     /**
    106      * <p> Is info 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 info. </p>
    111      *
    112      * @return true if info is enabled in the underlying logger.
    113      */
    114     public boolean isInfoEnabled();
    115
    116
    117     /**
    118      * <p> Is trace logging currently enabled? </p>
    119      *
    120      * <p> Call this method to prevent having to perform expensive operations
    121      * (for example, <code>String</code> concatenation)
    122      * when the log level is more than trace. </p>
    123      *
    124      * @return true if trace is enabled in the underlying logger.
    125      */
    126     public boolean isTraceEnabled();
    127
    128
    129     /**
    130      * <p> Is warn logging currently enabled? </p>
    131      *
    132      * <p> Call this method to prevent having to perform expensive operations
    133      * (for example, <code>String</code> concatenation)
    134      * when the log level is more than warn. </p>
    135      *
    136      * @return true if warn is enabled in the underlying logger.
    137      */
    138     public boolean isWarnEnabled();
    139
    140
    141     // -------------------------------------------------------- Logging Methods
    142
    143
    144     /**
    145      * <p> Log a message with trace log level. </p>
    146      *
    147      * @param message log this message
    148      */
    149     public void trace(Object message);
    150
    151
    152     /**
    153      * <p> Log an error with trace log level. </p>
    154      *
    155      * @param message log this message
    156      * @param t log this cause
    157      */
    158     public void trace(Object message, Throwable t);
    159
    160
    161     /**
    162      * <p> Log a message with debug log level. </p>
    163      *
    164      * @param message log this message
    165      */
    166     public void debug(Object message);
    167
    168
    169     /**
    170      * <p> Log an error with debug log level. </p>
    171      *
    172      * @param message log this message
    173      * @param t log this cause
    174      */
    175     public void debug(Object message, Throwable t);
    176
    177
    178     /**
    179      * <p> Log a message with info log level. </p>
    180      *
    181      * @param message log this message
    182      */
    183     public void info(Object message);
    184
    185
    186     /**
    187      * <p> Log an error with info log level. </p>
    188      *
    189      * @param message log this message
    190      * @param t log this cause
    191      */
    192     public void info(Object message, Throwable t);
    193
    194
    195     /**
    196      * <p> Log a message with warn log level. </p>
    197      *
    198      * @param message log this message
    199      */
    200     public void warn(Object message);
    201
    202
    203     /**
    204      * <p> Log an error with warn log level. </p>
    205      *
    206      * @param message log this message
    207      * @param t log this cause
    208      */
    209     public void warn(Object message, Throwable t);
    210
    211
    212     /**
    213      * <p> Log a message with error log level. </p>
    214      *
    215      * @param message log this message
    216      */
    217     public void error(Object message);
    218
    219
    220     /**
    221      * <p> Log an error with error log level. </p>
    222      *
    223      * @param message log this message
    224      * @param t log this cause
    225      */
    226     public void error(Object message, Throwable t);
    227
    228
    229     /**
    230      * <p> Log a message with fatal log level. </p>
    231      *
    232      * @param message log this message
    233      */
    234     public void fatal(Object message);
    235
    236
    237     /**
    238      * <p> Log an error with fatal log level. </p>
    239      *
    240      * @param message log this message
    241      * @param t log this cause
    242      */
    243     public void fatal(Object message, Throwable t);
    244
    245
    246 }