libjava/java/util/logging/Formatter.java

   1 /* Formatter.java
   2    -- a class for formatting log messages by localizing message texts
   3       and performing substitution of parameters
   4
   5 Copyright (C) 2002 Free Software Foundation, Inc.
   6
   7 This file is part of GNU Classpath.
   8
   9 GNU Classpath is free software; you can redistribute it and/or modify
  10 it under the terms of the GNU General Public License as published by
  11 the Free Software Foundation; either version 2, or (at your option)
  12 any later version.
  13
  14 GNU Classpath is distributed in the hope that it will be useful, but
  15 WITHOUT ANY WARRANTY; without even the implied warranty of
  16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  17 General Public License for more details.
  18
  19 You should have received a copy of the GNU General Public License
  20 along with GNU Classpath; see the file COPYING.  If not, write to the
  21 Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  22 02111-1307 USA.
  23
  24 Linking this library statically or dynamically with other modules is
  25 making a combined work based on this library.  Thus, the terms and
  26 conditions of the GNU General Public License cover the whole
  27 combination.
  28
  29 As a special exception, the copyright holders of this library give you
  30 permission to link this library with independent modules to produce an
  31 executable, regardless of the license terms of these independent
  32 modules, and to copy and distribute the resulting executable under
  33 terms of your choice, provided that you also meet, for each linked
  34 independent module, the terms and conditions of the license of that
  35 module.  An independent module is a module which is not derived from
  36 or based on this library.  If you modify this library, you may extend
  37 this exception to your version of the library, but you are not
  38 obligated to do so.  If you do not wish to do so, delete this
  39 exception statement from your version.
  40
  41 */
  42
  43
  44 package java.util.logging;
  45
  46 import java.util.ResourceBundle;
  47 import java.text.MessageFormat;
  48
  49 /**
  50  * A <code>Formatter</code> supports handlers by localizing
  51  * message texts and by subsituting parameter values for their
  52  * placeholders.
  53  *
  54  * @author Sascha Brawer (brawer@acm.org)
  55  */
  56 public abstract class Formatter
  57 {
  58   /**
  59    * Constructs a new Formatter.
  60    */
  61   protected Formatter()
  62   {
  63   }
  64
  65
  66   /**
  67    * Formats a LogRecord into a string.  Usually called by handlers
  68    * which need a string for a log record, for example to append
  69    * a record to a log file or to transmit a record over the network.
  70    *
  71    * @param record the log record for which a string form is requested.
  72    */
  73   public abstract String format(LogRecord record);
  74
  75
  76   /**
  77    * Returns a string that handlers are supposed to emit before
  78    * the first log record.  The base implementation returns an
  79    * empty string, but subclasses such as {@link XMLFormatter}
  80    * override this method in order to provide a suitable header.
  81    *
  82    * @return a string for the header.
  83    *
  84    * @param handler the handler which will prepend the returned
  85    *     string in front of the first log record.  This method
  86    *     may inspect certain properties of the handler, for
  87    *     example its encoding, in order to construct the header.
  88    */
  89   public String getHead(Handler handler)
  90   {
  91     return "";
  92   }
  93
  94
  95   /**
  96    * Returns a string that handlers are supposed to emit after
  97    * the last log record.  The base implementation returns an
  98    * empty string, but subclasses such as {@link XMLFormatter}
  99    * override this method in order to provide a suitable tail.
 100    *
 101    * @return a string for the header.
 102    *
 103    * @param handler the handler which will append the returned
 104    *     string after the last log record.  This method
 105    *     may inspect certain properties of the handler
 106    *     in order to construct the tail.
 107    */
 108   public String getTail(Handler handler)
 109   {
 110     return "";
 111   }
 112
 113
 114   /**
 115    * Formats the message part of a log record.
 116    *
 117    * <p>First, the Formatter localizes the record message to the
 118    * default locale by looking up the message in the record's
 119    * localization resource bundle.  If this step fails because there
 120    * is no resource bundle associated with the record, or because the
 121    * record message is not a key in the bundle, the raw message is
 122    * used instead.
 123    *
 124    * <p>Second, the Formatter substitutes appropriate strings for
 125    * the message parameters. If the record returns a non-empty
 126    * array for <code>getParameters()</code> and the localized
 127    * message string contains the character sequence "{0", the
 128    * formatter uses <code>java.text.MessageFormat</code> to format
 129    * the message.  Otherwise, no parameter substitution is performed.
 130    *
 131    * @param record the log record to be localized and formatted.
 132    *
 133    * @return the localized message text where parameters have been
 134    *         substituted by suitable strings.
 135    *
 136    * @throws NullPointerException if <code>record</code>
 137    *         is <code>null</code>.
 138    */
 139   public String formatMessage(LogRecord record)
 140   {
 141     String          msg;
 142     ResourceBundle  bundle;
 143     Object[]        params;
 144
 145     /* This will throw a NullPointerExceptionif record is null. */
 146     msg = record.getMessage();
 147     if (msg == null)
 148       msg = "";
 149
 150     /* Try to localize the message. */
 151     bundle = record.getResourceBundle();
 152     if (bundle != null)
 153     {
 154       try
 155       {
 156         msg = bundle.getString(msg);
 157       }
 158       catch (java.util.MissingResourceException _)
 159       {
 160       }
 161     }
 162
 163     /* Format the message if there are parameters. */
 164     params = record.getParameters();
 165     if ((params != null)
 166         && (params.length > 0)
 167         && (msg.indexOf("{0") >= 0))
 168     {
 169       msg = MessageFormat.format(msg, params);
 170     }
 171
 172     return msg;
 173   }
 174 }