Logger


1   /*
2    * Copyright (c) 2003 The Visigoth Software Society. All rights
3    * reserved.
4    *
5    * Redistribution and use in source and binary forms, with or without
6    * modification, are permitted provided that the following conditions
7    * are met:
8    *
9    * 1. Redistributions of source code must retain the above copyright
10   *    notice, this list of conditions and the following disclaimer.
11   *
12   * 2. Redistributions in binary form must reproduce the above copyright
13   *    notice, this list of conditions and the following disclaimer in
14   *    the documentation and/or other materials provided with the
15   *    distribution.
16   *
17   * 3. The end-user documentation included with the redistribution, if
18   *    any, must include the following acknowledgement:
19   *       "This product includes software developed by the
20   *        Visigoth Software Society (http://www.visigoths.org/)."
21   *    Alternately, this acknowledgement may appear in the software itself,
22   *    if and wherever such third-party acknowledgements normally appear.
23   *
24   * 4. Neither the name "FreeMarker", "Visigoth", nor any of the names of the
25   *    project contributors may be used to endorse or promote products derived
26   *    from this software without prior written permission. For written
27   *    permission, please contact visigoths@visigoths.org.
28   *
29   * 5. Products derived from this software may not be called "FreeMarker" or "Visigoth"
30   *    nor may "FreeMarker" or "Visigoth" appear in their names
31   *    without prior written permission of the Visigoth Software Society.
32   *
33   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
34   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
35   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
36   * DISCLAIMED.  IN NO EVENT SHALL THE VISIGOTH SOFTWARE SOCIETY OR
37   * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
38   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
39   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
40   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
41   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
42   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
43   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
44   * SUCH DAMAGE.
45   * ====================================================================
46   *
47   * This software consists of voluntary contributions made by many
48   * individuals on behalf of the Visigoth Software Society. For more
49   * information on the Visigoth Software Society, please see
50   * http://www.visigoths.org/
51   */
52  
53  package freemarker.log;
54  
55  import java.util.HashMap  ;
56  import java.util.Map  ;
57  
58  import freemarker.template.utility.ClassUtil;
59  
60  /**
61   * The FreeMarker logging facility. This is a polymorphic implementation
62   * that will use whatever logging package it can find on the system:
63   * Apache Jakarta Log4J, Apache Jakarta Avalon LogKit, JDK1.4 logging
64   * (in this order). If it fails to find any of the above, logging will
65   * be suppressed and a short notice output to System.err. You can use the
66   * {@link #selectLoggerLibrary(int)} static method to force use of a specific
67   * logger package, or to turn off logging.
68   * @version $Id: Logger.java,v 1.24 2003/10/03 15:35:10 stephanmueller Exp $
69   * @author Attila Szegedi
70   */
71  public abstract class Logger
72  {
73      /**
74       * Constant used with {@link #selectLoggerLibrary(int)} that indicates the
75       * engine should automatically lookup and use any available logger library.
76       */
77      public static final int LIBRARY_AUTO = -1;
78      /**
79       * Constant used with {@link #selectLoggerLibrary(int)} that indicates the
80       * engine should use no logger package (i.e. turn off logging).
81       */
82      public static final int LIBRARY_NONE = 0;
83      /**
84       * Constant used with {@link #selectLoggerLibrary(int)} that indicates the
85       * engine should use the <tt>java.util.logging</tt> logger package.
86       */
87      public static final int LIBRARY_JAVA = 1;
88      /**
89       * Constant used with {@link #selectLoggerLibrary(int)} that indicates the
90       * engine should use the Apache Jakarta Avalon LogKit logger package.
91       */
92      public static final int LIBRARY_AVALON = 2;
93      /**
94       * Constant used with {@link #selectLoggerLibrary(int)} that indicates the
95       * engine should use the Apache Jakarta Log4J logger package.
96       */
97      public static final int LIBRARY_LOG4J = 3;
98  
99      private static final String  [] LIBINIT =
100     {
101         "freemarker.log", "Null",
102         "java.util.logging", "JDK14",
103         "org.apache.log",    "Avalon",
104         "org.apache.log4j",  "Log4J"
105     };
106 
107     private static int logLibrary;
108     private static LoggerFactory factory;
109     private static String   categoryPrefix = "";
110 
111     private static final Map   loggers = new HashMap  ();
112 
113     /**
114      * Selects the logger library to use.
115      * If you want to change the default setting, do it early in application
116      * initialization phase, before calling any other FreeMarker API since once
117      * various parts of the FreeMarker library bind to the logging subsystem,
118      * the change in this value will have no effect on them.
119      * @param library one of <tt>LIBRARY_XXX</tt> constants. By default,
120      * {@link #LIBRARY_AUTO} is used.
121      * @throws ClassNotFoundException if an explicit logging library is asked for
122      * (that is, neither NONE, nor AUTO), and it is not found in the classpath.
123      */
124     public static void selectLoggerLibrary(int library)
125     throws
126         ClassNotFoundException  
127     {
128         synchronized (Logger.class) {
129             if(library < -1 || (library*2) >= LIBINIT.length)
130             {
131                 throw new IllegalArgumentException  ();
132             }
133             logLibrary = library;
134             factory = createFactory();
135         }
136     }
137 
138     /**
139      * Sets a category prefix. This prefix is prepended to any logger category
140      * name. This makes it possible to have different FreeMarker logger categories
141      * on a per-application basis (better said, per-classloader basis). By default
142      * the category prefix is the empty string. If you set a non-empty category
143      * prefix, be sure to include the trailing separator dot (i.e. "MyApp.")
144      * If you want to change the default setting, do it early in application
145      * initialization phase, before calling any other FreeMarker API since once
146      * various parts of the FreeMarker library bind to the logging subsystem,
147      * the change in this value will have no effect on them.
148      */
149     public static void setCategoryPrefix(String   prefix)
150     {
151         synchronized (Logger.class) {
152             if(prefix == null)
153             {
154                 throw new IllegalArgumentException  ();
155             }
156             categoryPrefix = prefix;
157         }
158     }
159 
160     /**
161      * Logs a debugging message.
162      */
163     public abstract void debug(String   message);
164 
165     /**
166      * Logs a debugging message with accompanying throwable.
167      */
168     public abstract void debug(String   message, Throwable   t);
169 
170     /**
171      * Logs an informational message.
172      */
173     public abstract void info(String   message);
174 
175     /**
176      * Logs an informational message with accompanying throwable.
177      */
178     public abstract void info(String   message, Throwable   t);
179 
180     /**
181      * Logs a warning message.
182      */
183     public abstract void warn(String   message);
184 
185     /**
186      * Logs a warning message with accompanying throwable.
187      */
188     public abstract void warn(String   message, Throwable   t);
189 
190     /**
191      * Logs an error message.
192      */
193     public abstract void error(String   message);
194 
195     /**
196      * Logs an error message with accompanying throwable.
197      */
198     public abstract void error(String   message, Throwable   t);
199 
200     /**
201      * Returns true if this logger will log debug messages.
202      */
203     public abstract boolean isDebugEnabled();
204 
205     /**
206      * Returns true if this logger will log informational messages.
207      */
208     public abstract boolean isInfoEnabled();
209 
210     /**
211      * Returns true if this logger will log warning messages.
212      */
213     public abstract boolean isWarnEnabled();
214 
215     /**
216      * Returns true if this logger will log error messages.
217      */
218     public abstract boolean isErrorEnabled();
219 
220     /**
221      * Returns true if this logger will log fatal error messages.
222      */
223     public abstract boolean isFatalEnabled();
224 
225     /**
226      * Returns a logger for the specified category.
227      * @param category a dot separated hierarchical category name. If a category
228      * prefix is in effect, it is prepended to the category name.
229      */
230     public static Logger getLogger(String   category)
231     {
232         if (factory == null) {
233             synchronized (Logger.class) {
234                 if (factory == null) {
235                     try
236                     {
237                         selectLoggerLibrary(LIBRARY_AUTO);
238                     }
239                     catch(ClassNotFoundException   e)
240                     {
241                         // This can't happen, really
242                         throw new RuntimeException  (e.getMessage());
243                     }
244                 }
245             }
246         }
247 
248         category = categoryPrefix + category;
249 
250         synchronized(loggers)
251         {
252             Logger logger = (Logger)loggers.get(category);
253             if(logger == null)
254             {
255                 logger = factory.getLogger(category);
256                 loggers.put(category, logger);
257             }
258             return logger;
259         }
260     }
261 
262     private static LoggerFactory createFactory()
263     throws
264         ClassNotFoundException  
265     {
266         if(logLibrary == LIBRARY_AUTO)
267         {
268             for(int i = LIBINIT.length / 2 - 1; i > 0; --i)
269             {
270                 try
271                 {
272                     return createFactory(i);
273                 }
274                 catch(ClassNotFoundException   e)
275                 {
276                     ;//Intentionally ignored
277                 }
278             }
279             System.err.println("*** WARNING: FreeMarker logging suppressed.");
280             return new NullLoggerFactory();
281         }
282         else
283         {
284             return createFactory(logLibrary);
285         }
286     }
287 
288     private static LoggerFactory createFactory(int library)
289     throws
290         ClassNotFoundException  
291     {
292         String   requiredPackage = LIBINIT[library * 2];
293         String   factoryType = LIBINIT[library * 2 + 1];
294 
295         try
296         {
297             ClassUtil.forName(requiredPackage + ".Logger");
298             return (LoggerFactory)Class.forName("freemarker.log." + factoryType + "LoggerFactory").newInstance();
299         }
300         catch(IllegalAccessException   e)
301         {
302             // This can't happen, really
303             throw new IllegalAccessError  (e.getMessage());
304         }
305         catch(InstantiationException   e)
306         {
307             // This can't happen, really
308             throw new InstantiationError  (e.getMessage());
309         }
310     }
311 }
312
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