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    1   /*
    2    * Copyright 2001-2004 The Apache Software Foundation.
    3    *
    4    * Licensed under the Apache License, Version 2.0 (the "License");
    5    * you may not use this file except in compliance with the License.
    6    * You may obtain a copy of the License at
    7    *
    8    *      http://www.apache.org/licenses/LICENSE-2.0
    9    *
    10   * Unless required by applicable law or agreed to in writing, software
    11   * distributed under the License is distributed on an "AS IS" BASIS,
    12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13   * See the License for the specific language governing permissions and
    14   * limitations under the License.
    15   */
    16
    17  package org.apache.commons.logging;
    18
    19  /**
    20   * <p>A simple logging interface abstracting logging APIs.  In order to be
    21   * instantiated successfully by {@link LogFactory}, classes that implement
    22   * this interface must have a constructor that takes a single String
    23   * parameter representing the "name" of this Log.</p>
    24   *
    25   * <p> The six logging levels used by <code>Log</code> are (in order):
    26   * <ol>
    27   * <li>trace (the least serious)</li>
    28   * <li>debug</li>
    29   * <li>info</li>
    30   * <li>warn</li>
    31   * <li>error</li>
    32   * <li>fatal (the most serious)</li>
    33   * </ol>
    34   * The mapping of these log levels to the concepts used by the underlying
    35   * logging system is implementation dependent.
    36   * The implementation should ensure, though, that this ordering behaves
    37   * as expected.</p>
    38   *
    39   * <p>Performance is often a logging concern.
    40   * By examining the appropriate property,
    41   * a component can avoid expensive operations (producing information
    42   * to be logged).</p>
    43   *
    44   * <p> For example,
    45   * <code><pre>
    46   *    if (log.isDebugEnabled()) {
    47   *        ... do something expensive ...
    48   *        log.debug(theResult);
    49   *    }
    50   * </pre></code>
    51   * </p>
    52   *
    53   * <p>Configuration of the underlying logging system will generally be done
    54   * external to the Logging APIs, through whatever mechanism is supported by
    55   * that system.</p>
    56   *
    57   * <p style="color: #E40; font-weight: bold;">Please note that this interface is identical to that found in JCL 1.1.1.</p>
    58   *
    59   * @author <a href="mailto:sanders@apache.org">Scott Sanders</a>
    60   * @author Rod Waldhoff
    61   * @version $Id: Log.java,v 1.19 2004/06/06 21:16:04 rdonkin Exp $
    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      public boolean isDebugEnabled();
    77
    78
    79      /**
    80       * <p> Is error logging currently enabled? </p>
    81       *
    82       * <p> Call this method to prevent having to perform expensive operations
    83       * (for example, <code>String</code> concatenation)
    84       * when the log level is more than error. </p>
    85       */
    86      public boolean isErrorEnabled();
    87
    88
    89      /**
    90       * <p> Is fatal logging currently enabled? </p>
    91       *
    92       * <p> Call this method to prevent having to perform expensive operations
    93       * (for example, <code>String</code> concatenation)
    94       * when the log level is more than fatal. </p>
    95       */
    96      public boolean isFatalEnabled();
    97
    98
    99      /**
    100      * <p> Is info logging currently enabled? </p>
    101      *
    102      * <p> Call this method to prevent having to perform expensive operations
    103      * (for example, <code>String</code> concatenation)
    104      * when the log level is more than info. </p>
    105      *
    106      * @return true if info enabled, false otherwise
    107      */
    108     public boolean isInfoEnabled();
    109
    110
    111     /**
    112      * <p> Is trace logging currently enabled? </p>
    113      *
    114      * <p> Call this method to prevent having to perform expensive operations
    115      * (for example, <code>String</code> concatenation)
    116      * when the log level is more than trace. </p>
    117      *
    118      * @return true if trace enabled, false otherwise
    119      */
    120     public boolean isTraceEnabled();
    121
    122
    123     /**
    124      * <p> Is warn logging currently enabled? </p>
    125      *
    126      * <p> Call this method to prevent having to perform expensive operations
    127      * (for example, <code>String</code> concatenation)
    128      * when the log level is more than warn. </p>
    129      */
    130     public boolean isWarnEnabled();
    131
    132
    133     // -------------------------------------------------------- Logging Methods
    134
    135
    136     /**
    137      * <p> Log a message with trace log level. </p>
    138      *
    139      * @param message log this message
    140      */
    141     public void trace(Object message);
    142
    143
    144     /**
    145      * <p> Log an error with trace log level. </p>
    146      *
    147      * @param message log this message
    148      * @param t log this cause
    149      */
    150     public void trace(Object message, Throwable t);
    151
    152
    153     /**
    154      * <p> Log a message with debug log level. </p>
    155      *
    156      * @param message log this message
    157      */
    158     public void debug(Object message);
    159
    160
    161     /**
    162      * <p> Log an error with debug log level. </p>
    163      *
    164      * @param message log this message
    165      * @param t log this cause
    166      */
    167     public void debug(Object message, Throwable t);
    168
    169
    170     /**
    171      * <p> Log a message with info log level. </p>
    172      *
    173      * @param message log this message
    174      */
    175     public void info(Object message);
    176
    177
    178     /**
    179      * <p> Log an error with info log level. </p>
    180      *
    181      * @param message log this message
    182      * @param t log this cause
    183      */
    184     public void info(Object message, Throwable t);
    185
    186
    187     /**
    188      * <p> Log a message with warn log level. </p>
    189      *
    190      * @param message log this message
    191      */
    192     public void warn(Object message);
    193
    194
    195     /**
    196      * <p> Log an error with warn log level. </p>
    197      *
    198      * @param message log this message
    199      * @param t log this cause
    200      */
    201     public void warn(Object message, Throwable t);
    202
    203
    204     /**
    205      * <p> Log a message with error log level. </p>
    206      *
    207      * @param message log this message
    208      */
    209     public void error(Object message);
    210
    211
    212     /**
    213      * <p> Log an error with error log level. </p>
    214      *
    215      * @param message log this message
    216      * @param t log this cause
    217      */
    218     public void error(Object message, Throwable t);
    219
    220
    221     /**
    222      * <p> Log a message with fatal log level. </p>
    223      *
    224      * @param message log this message
    225      */
    226     public void fatal(Object message);
    227
    228
    229     /**
    230      * <p> Log an error with fatal log level. </p>
    231      *
    232      * @param message log this message
    233      * @param t log this cause
    234      */
    235     public void fatal(Object message, Throwable t);
    236
    237
    238 }