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
17package 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 */
63public 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}
218