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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  
18  package org.apache.commons.logging;
19  
20  /***
21   * <p>A simple logging interface abstracting logging APIs.  In order to be
22   * instantiated successfully by {@link LogFactory}, classes that implement
23   * this interface must have a constructor that takes a single String
24   * parameter representing the "name" of this Log.</p>
25   *
26   * <p> The six logging levels used by <code>Log</code> are (in order):
27   * <ol>
28   * <li>trace (the least serious)</li>
29   * <li>debug</li>
30   * <li>info</li>
31   * <li>warn</li>
32   * <li>error</li>
33   * <li>fatal (the most serious)</li>
34   * </ol>
35   * The mapping of these log levels to the concepts used by the underlying
36   * logging system is implementation dependent.
37   * The implemention should ensure, though, that this ordering behaves
38   * as expected.</p>
39   *
40   * <p>Performance is often a logging concern.
41   * By examining the appropriate property,
42   * a component can avoid expensive operations (producing information
43   * to be logged).</p>
44   *
45   * <p> For example,
46   * <code><pre>
47   *    if (log.isDebugEnabled()) {
48   *        ... do something expensive ...
49   *        log.debug(theResult);
50   *    }
51   * </pre></code>
52   * </p>
53   *
54   * <p>Configuration of the underlying logging system will generally be done
55   * external to the Logging APIs, through whatever mechanism is supported by
56   * that system.</p>
57   *
58   * @author <a href="mailto:sanders@apache.org">Scott Sanders</a>
59   * @author Rod Waldhoff
60   * @version $Id: Log.java,v 1.19 2004/06/06 21:16:04 rdonkin Exp $
61   */
62  public interface Log {
63  
64  
65      // ----------------------------------------------------- Logging Properties
66  
67  
68      /***
69       * <p> Is debug logging currently enabled? </p>
70       *
71       * <p> Call this method to prevent having to perform expensive operations
72       * (for example, <code>String</code> concatenation)
73       * when the log level is more than debug. </p>
74       */
75      public boolean isDebugEnabled();
76  
77  
78      /***
79       * <p> Is error logging currently enabled? </p>
80       *
81       * <p> Call this method to prevent having to perform expensive operations
82       * (for example, <code>String</code> concatenation)
83       * when the log level is more than error. </p>
84       */
85      public boolean isErrorEnabled();
86  
87  
88      /***
89       * <p> Is fatal logging currently enabled? </p>
90       *
91       * <p> Call this method to prevent having to perform expensive operations
92       * (for example, <code>String</code> concatenation)
93       * when the log level is more than fatal. </p>
94       */
95      public boolean isFatalEnabled();
96  
97  
98      /***
99       * <p> Is info logging currently enabled? </p>
100      *
101      * <p> Call this method to prevent having to perform expensive operations
102      * (for example, <code>String</code> concatenation)
103      * when the log level is more than info. </p>
104      */
105     public boolean isInfoEnabled();
106 
107 
108     /***
109      * <p> Is trace logging currently enabled? </p>
110      *
111      * <p> Call this method to prevent having to perform expensive operations
112      * (for example, <code>String</code> concatenation)
113      * when the log level is more than trace. </p>
114      */
115     public boolean isTraceEnabled();
116 
117 
118     /***
119      * <p> Is warn logging currently enabled? </p>
120      *
121      * <p> Call this method to prevent having to perform expensive operations
122      * (for example, <code>String</code> concatenation)
123      * when the log level is more than warn. </p>
124      */
125     public boolean isWarnEnabled();
126 
127 
128     // -------------------------------------------------------- Logging Methods
129 
130 
131     /***
132      * <p> Log a message with trace log level. </p>
133      *
134      * @param message log this message
135      */
136     public void trace(Object message);
137 
138 
139     /***
140      * <p> Log an error with trace log level. </p>
141      *
142      * @param message log this message
143      * @param t log this cause
144      */
145     public void trace(Object message, Throwable t);
146 
147 
148     /***
149      * <p> Log a message with debug log level. </p>
150      *
151      * @param message log this message
152      */
153     public void debug(Object message);
154 
155 
156     /***
157      * <p> Log an error with debug log level. </p>
158      *
159      * @param message log this message
160      * @param t log this cause
161      */
162     public void debug(Object message, Throwable t);
163 
164 
165     /***
166      * <p> Log a message with info log level. </p>
167      *
168      * @param message log this message
169      */
170     public void info(Object message);
171 
172 
173     /***
174      * <p> Log an error with info log level. </p>
175      *
176      * @param message log this message
177      * @param t log this cause
178      */
179     public void info(Object message, Throwable t);
180 
181 
182     /***
183      * <p> Log a message with warn log level. </p>
184      *
185      * @param message log this message
186      */
187     public void warn(Object message);
188 
189 
190     /***
191      * <p> Log an error with warn log level. </p>
192      *
193      * @param message log this message
194      * @param t log this cause
195      */
196     public void warn(Object message, Throwable t);
197 
198 
199     /***
200      * <p> Log a message with error log level. </p>
201      *
202      * @param message log this message
203      */
204     public void error(Object message);
205 
206 
207     /***
208      * <p> Log an error with error log level. </p>
209      *
210      * @param message log this message
211      * @param t log this cause
212      */
213     public void error(Object message, Throwable t);
214 
215 
216     /***
217      * <p> Log a message with fatal log level. </p>
218      *
219      * @param message log this message
220      */
221     public void fatal(Object message);
222 
223 
224     /***
225      * <p> Log an error with fatal log level. </p>
226      *
227      * @param message log this message
228      * @param t log this cause
229      */
230     public void fatal(Object message, Throwable t);
231 
232 
233 }