001/* Formatter.java --
002   A class for formatting log messages by localizing message texts
003   and performing substitution of parameters
004   Copyright (C) 2002, 2004 Free Software Foundation, Inc.
005
006This file is part of GNU Classpath.
007
008GNU Classpath is free software; you can redistribute it and/or modify
009it under the terms of the GNU General Public License as published by
010the Free Software Foundation; either version 2, or (at your option)
011any later version.
012
013GNU Classpath is distributed in the hope that it will be useful, but
014WITHOUT ANY WARRANTY; without even the implied warranty of
015MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
016General Public License for more details.
017
018You should have received a copy of the GNU General Public License
019along with GNU Classpath; see the file COPYING.  If not, write to the
020Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02102110-1301 USA.
022
023Linking this library statically or dynamically with other modules is
024making a combined work based on this library.  Thus, the terms and
025conditions of the GNU General Public License cover the whole
026combination.
027
028As a special exception, the copyright holders of this library give you
029permission to link this library with independent modules to produce an
030executable, regardless of the license terms of these independent
031modules, and to copy and distribute the resulting executable under
032terms of your choice, provided that you also meet, for each linked
033independent module, the terms and conditions of the license of that
034module.  An independent module is a module which is not derived from
035or based on this library.  If you modify this library, you may extend
036this exception to your version of the library, but you are not
037obligated to do so.  If you do not wish to do so, delete this
038exception statement from your version. */
039
040
041package java.util.logging;
042
043import java.text.MessageFormat;
044import java.util.ResourceBundle;
045
046/**
047 * A <code>Formatter</code> supports handlers by localizing
048 * message texts and by subsituting parameter values for their
049 * placeholders.
050 *
051 * @author Sascha Brawer (brawer@acm.org)
052 */
053public abstract class Formatter
054{
055  /**
056   * Constructs a new Formatter.
057   */
058  protected Formatter()
059  {
060  }
061
062
063  /**
064   * Formats a LogRecord into a string.  Usually called by handlers
065   * which need a string for a log record, for example to append
066   * a record to a log file or to transmit a record over the network.
067   *
068   * @param record the log record for which a string form is requested.
069   */
070  public abstract String format(LogRecord record);
071
072
073  /**
074   * Returns a string that handlers are supposed to emit before
075   * the first log record.  The base implementation returns an
076   * empty string, but subclasses such as {@link XMLFormatter}
077   * override this method in order to provide a suitable header.
078   *
079   * @return a string for the header.
080   *
081   * @param handler the handler which will prepend the returned
082   *     string in front of the first log record.  This method
083   *     may inspect certain properties of the handler, for
084   *     example its encoding, in order to construct the header.
085   */
086  public String getHead(Handler handler)
087  {
088    return "";
089  }
090
091
092  /**
093   * Returns a string that handlers are supposed to emit after
094   * the last log record.  The base implementation returns an
095   * empty string, but subclasses such as {@link XMLFormatter}
096   * override this method in order to provide a suitable tail.
097   *
098   * @return a string for the header.
099   *
100   * @param handler the handler which will append the returned
101   *     string after the last log record.  This method
102   *     may inspect certain properties of the handler
103   *     in order to construct the tail.
104   */
105  public String getTail(Handler handler)
106  {
107    return "";
108  }
109
110
111  /**
112   * Formats the message part of a log record.
113   *
114   * <p>First, the Formatter localizes the record message to the
115   * default locale by looking up the message in the record's
116   * localization resource bundle.  If this step fails because there
117   * is no resource bundle associated with the record, or because the
118   * record message is not a key in the bundle, the raw message is
119   * used instead.
120   *
121   * <p>Second, the Formatter substitutes appropriate strings for
122   * the message parameters. If the record returns a non-empty
123   * array for <code>getParameters()</code> and the localized
124   * message string contains the character sequence "{0", the
125   * formatter uses <code>java.text.MessageFormat</code> to format
126   * the message.  Otherwise, no parameter substitution is performed.
127   *
128   * @param record the log record to be localized and formatted.
129   *
130   * @return the localized message text where parameters have been
131   *         substituted by suitable strings.
132   *
133   * @throws NullPointerException if <code>record</code>
134   *         is <code>null</code>.
135   */
136  public String formatMessage(LogRecord record)
137  {
138    String          msg;
139    ResourceBundle  bundle;
140    Object[]        params;
141
142    /* This will throw a NullPointerExceptionif record is null. */
143    msg = record.getMessage();
144    if (msg == null)
145      msg = "";
146
147    /* Try to localize the message. */
148    bundle = record.getResourceBundle();
149    if (bundle != null)
150    {
151      try
152      {
153        msg = bundle.getString(msg);
154      }
155      catch (java.util.MissingResourceException _)
156      {
157      }
158    }
159
160    /* Format the message if there are parameters. */
161    params = record.getParameters();
162    if ((params != null)
163        && (params.length > 0)
164        && (msg.indexOf("{0") >= 0))
165    {
166      msg = MessageFormat.format(msg, params);
167    }
168
169    return msg;
170  }
171}