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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      // ----------------------------------------------------- Logging Properties
    66
    67      /**
    68       * <p> Is debug logging currently enabled? </p>
    69       *
    70       * <p> Call this method to prevent having to perform expensive operations
    71       * (for example, <code>String</code> concatenation)
    72       * when the log level is more than debug. </p>
    73       */
    74      public boolean isDebugEnabled();
    75
    76      /**
    77       * <p> Is error logging currently enabled? </p>
    78       *
    79       * <p> Call this method to prevent having to perform expensive operations
    80       * (for example, <code>String</code> concatenation)
    81       * when the log level is more than error. </p>
    82       */
    83      public boolean isErrorEnabled();
    84
    85      /**
    86       * <p> Is fatal logging currently enabled? </p>
    87       *
    88       * <p> Call this method to prevent having to perform expensive operations
    89       * (for example, <code>String</code> concatenation)
    90       * when the log level is more than fatal. </p>
    91       */
    92      public boolean isFatalEnabled();
    93
    94      /**
    95       * <p> Is info logging currently enabled? </p>
    96       *
    97       * <p> Call this method to prevent having to perform expensive operations
    98       * (for example, <code>String</code> concatenation)
    99       * 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 }