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}