Logger


1   /**
2   
3       Copyright (C) 2002-2003  Together
4   
5       This library is free software; you can redistribute it and/or
6       modify it under the terms of the GNU Lesser General Public
7       License as published by the Free Software Foundation; either
8       version 2.1 of the License, or (at your option) any later version.
9   
10      This library is distributed in the hope that it will be useful,
11      but WITHOUT ANY WARRANTY; without even the implied warranty of
12      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
13      Lesser General Public License for more details.
14  
15      You should have received a copy of the GNU Lesser General Public
16      License along with this library; if not, write to the Free Software
17      Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
18  
19   Logger.java
20   Date: 02.12.2003.
21   @version 1.0.0
22   @authors:
23   Milosevic Sinisa sinisa@prozone.co.yu
24   Radoslav Dutina rale@prozone.co.yu
25   Zoran Milakovic zoran@prozone.co.yu
26   */
27  package org.webdocwf.util.loader.logging;
28  
29  import java.io.IOException  ;
30  
31  
32  /**
33   * A general-purpose logging facility.  It is modeled after
34   * <CODE>syslogd</CODE>.  This is a base class from which an actual
35   * implementation is derived.  It only defines how log message are written
36   * by a client.  Where the log message is written and the mechanism for
37   * controlling logging is left up to the implementation.  This class does
38   * not define any of these mechanism and their definition is not necessary
39   * for understand how to use this class. <P>
40   *
41   * Each log message is associate with a facility and has a level assigned
42   * to it.  A facility is a symbolic (String) name that defines a class of
43   * log messages.  A level is used to indicate the
44   *
45   It is expected that the implementation can enable, disable and
46   * direct log messages based on these attributes.  Facilities and levels
47   * are defined symbolicly, with no restriction on the name, and form a tuple.
48   * Several standard levels are defined as integer constants and their use
49   * is expected to be higher performing than symbolic levels..<P>
50   *
51   *
52   *Normally, a single,
53   global instance of the object
54   * is exists and is obtainable by a static method in this class.<P>
55   *
56   * Log messages are written via an object implementing <CODE>LogChannel</CODE>.
57   * A channel is associated with a single facility, with the level being
58   * specified when a message is written.  Normally, a <CODE>LogChannel</CODE>
59   * is obtained once at initialization time and use repeatedly.  It is
60   * permissible to obtain multiple references to the log channel for a facility,
61   * but this is discouraged for performance reasons.<P>
62   *
63   * Log messages, even debugging ones, should be defined with care.  They
64   * should be terse, but clear to someone who isn't intimately familiar with
65   * the code.  Permanent debugging messages should be designed with the idea
66   * of use when supportting a deployed product.<P>
67   *
68   * The central logging object needs to be configured very early in the startup
69   * process.  If logging can't be configured, then the startup should be aborted
70   * or a object created that does some simple form of logging, such as write
71   * to <CODE>stderr<CODE>.  A client should never have to check if the global
72   * logger object exists.<P>
73   *
74   */
75  public abstract class Logger {
76  
77      /**
78       * Standard level.
79       */
80      public static final int LOGMODE_NORMAL = 1;
81  
82      /**
83       * A condition that should be corrected immediately
84       */
85      public static final int LOGMODE_NONE = 0;
86  
87      /**
88       * Critical conditions.
89       */
90      public static final int LOGMODE_FULL = 2;
91  
92      public static final String   strLOGMODE_NONE = "NONE";
93      public static final String   strLOGMODE_NORMAL = "NORMAL";
94      public static final String   strLOGMODE_FULL = "FULL";
95  
96      public boolean[] enbledLogLevels;
97  
98      /**
99       * Global <CODE>Logger</CODE> object.
100      */
101     protected static Logger centralLogger;
102 
103     /**
104      * Table of standard level names
105      */
106     protected static final String  [] standardLevelNames = {
107         strLOGMODE_NORMAL, // 0
108         strLOGMODE_NONE,  // 1
109         strLOGMODE_FULL  // 2
110     };
111 
112     /**
113      * Get the central (global) logging object.
114      *
115      * @return A reference the object.  If the facility has not been
116      *  initialized <CODE>null</CODE> is returned.  However, this is
117      *  considered a bug in the design of the initialization. Clients
118      *  do not need to check for <CODE>null</CODE>.
119      */
120     public static Logger getCentralLogger() {
121         return centralLogger;
122     }
123 
124     /**
125      * Configure Logger with given config file, interpreting of config file is
126      * logger implementation specific.
127      *
128      * @param confFilePath Path to configuration file.
129      * @throws Exception
130      */
131     abstract public void configure(String   confFilePath) throws Exception  ;
132 
133     /**
134      * Determine if logging is enabled for the specified level.  This
135      * is useful to prevent a series of unnecessary logging calls,
136      * as often encountered with debug logging, or a call where generating
137      * the message is expensive.
138      *
139      * @param level Numeric level that is to be checked.
140      * @return <CODE>true</CODE> if enabled, <CODE>false</CODE> if not
141      *         enabled.
142      */
143     abstract public boolean isEnabled(int level);
144 
145     /**
146      * Determine if logging is enabled for the specified level.  This
147      * is useful to prevent a series of unnecessary logging calls,
148      * as often encountered with debug logging, or a call where generating
149      * the message is expensive.
150      *
151      * @param level Symbolic level that is to be checked.
152      * @return <CODE>true</CODE> if enabled, <CODE>false</CODE> if not
153      *         enabled.
154      */
155     abstract public boolean isEnabled(String   level);
156 
157     /**
158      * Convert a symbolic level to an integer identifier.
159      *
160      * @param level Symbolic level to convert
161      * @return The numeric level identifier
162      */
163     abstract public int getLevel(String   level);
164 
165 
166     /**
167      * Write a string to the log file.
168      *
169      * @param level Numeric level the message is associated with.
170      * @param msg The message to log.
171      */
172     abstract public void write(int level, String   msg);
173 
174     /**
175      * Write a string to the log file.
176      *
177      * @param level Symbolic level the message is associated with.
178      * @param msg The message to log.
179      */
180     abstract public void write(String   level, String   msg);
181 
182     /**
183      * Write a string and exception to the log file.
184      *
185      * @param level Numeric level the message is associated with.
186      * @param msg The message to log.
187      * @param throwable Exception or error to log.
188      */
189     abstract public void write(int level, String   msg, Throwable   throwable);
190 
191     /**
192      * Write a string and exception to the log file.
193      *
194      * @param level Symbolic level the message is associated with.
195      * @param msg The message to log.
196      * @param throwable Exception or error to log.
197      */
198     abstract public void write(String   level, String   msg, Throwable   throwable);
199 
200     abstract public boolean[] getEnabledLogLevels();
201 
202     abstract public void setEnabledLogLevels(String   logMode);
203 
204     abstract public boolean setMessage(String   key, String   value);
205 
206     abstract public String   getMessage(String   key);
207 
208     abstract public boolean writeEcho (String   strLogTxt);
209 
210     abstract public void close();
211   }
212 
213
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