MemoryHandler.java revision 51b1b6997fd3f980076b8081f7f1165ccc2a4008
1/* 2 * Copyright (c) 2000, 2004, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26package java.util.logging; 27 28/** 29 * <tt>Handler</tt> that buffers requests in a circular buffer in memory. 30 * <p> 31 * Normally this <tt>Handler</tt> simply stores incoming <tt>LogRecords</tt> 32 * into its memory buffer and discards earlier records. This buffering 33 * is very cheap and avoids formatting costs. On certain trigger 34 * conditions, the <tt>MemoryHandler</tt> will push out its current buffer 35 * contents to a target <tt>Handler</tt>, which will typically publish 36 * them to the outside world. 37 * <p> 38 * There are three main models for triggering a push of the buffer: 39 * <ul> 40 * <li> 41 * An incoming <tt>LogRecord</tt> has a type that is greater than 42 * a pre-defined level, the <tt>pushLevel</tt>. 43 * <li> 44 * An external class calls the <tt>push</tt> method explicitly. 45 * <li> 46 * A subclass overrides the <tt>log</tt> method and scans each incoming 47 * <tt>LogRecord</tt> and calls <tt>push</tt> if a record matches some 48 * desired criteria. 49 * </ul> 50 * <p> 51 * <b>Configuration:</b> 52 * By default each <tt>MemoryHandler</tt> is initialized using the following 53 * LogManager configuration properties. If properties are not defined 54 * (or have invalid values) then the specified default values are used. 55 * If no default value is defined then a RuntimeException is thrown. 56 * <ul> 57 * <li> java.util.logging.MemoryHandler.level 58 * specifies the level for the <tt>Handler</tt> 59 * (defaults to <tt>Level.ALL</tt>). 60 * <li> java.util.logging.MemoryHandler.filter 61 * specifies the name of a <tt>Filter</tt> class to use 62 * (defaults to no <tt>Filter</tt>). 63 * <li> java.util.logging.MemoryHandler.size 64 * defines the buffer size (defaults to 1000). 65 * <li> java.util.logging.MemoryHandler.push 66 * defines the <tt>pushLevel</tt> (defaults to <tt>level.SEVERE</tt>). 67 * <li> java.util.logging.MemoryHandler.target 68 * specifies the name of the target <tt>Handler </tt> class. 69 * (no default). 70 * </ul> 71 * 72 * @since 1.4 73 */ 74 75public class MemoryHandler extends Handler { 76 private final static int DEFAULT_SIZE = 1000; 77 private Level pushLevel; 78 private int size; 79 private Handler target; 80 private LogRecord buffer[]; 81 int start, count; 82 83 // Private method to configure a ConsoleHandler from LogManager 84 // properties and/or default values as specified in the class 85 // javadoc. 86 private void configure() { 87 LogManager manager = LogManager.getLogManager(); 88 String cname = getClass().getName(); 89 90 pushLevel = manager.getLevelProperty(cname +".push", Level.SEVERE); 91 size = manager.getIntProperty(cname + ".size", DEFAULT_SIZE); 92 if (size <= 0) { 93 size = DEFAULT_SIZE; 94 } 95 setLevel(manager.getLevelProperty(cname +".level", Level.ALL)); 96 setFilter(manager.getFilterProperty(cname +".filter", null)); 97 setFormatter(manager.getFormatterProperty(cname +".formatter", new SimpleFormatter())); 98 } 99 100 /** 101 * Create a <tt>MemoryHandler</tt> and configure it based on 102 * <tt>LogManager</tt> configuration properties. 103 */ 104 public MemoryHandler() { 105 sealed = false; 106 configure(); 107 sealed = true; 108 109 String name = "???"; 110 try { 111 LogManager manager = LogManager.getLogManager(); 112 name = manager.getProperty("java.util.logging.MemoryHandler.target"); 113 Class clz = ClassLoader.getSystemClassLoader().loadClass(name); 114 target = (Handler) clz.newInstance(); 115 } catch (Exception ex) { 116 throw new RuntimeException("MemoryHandler can't load handler \"" + name + "\"" , ex); 117 } 118 init(); 119 } 120 121 // Initialize. Size is a count of LogRecords. 122 private void init() { 123 buffer = new LogRecord[size]; 124 start = 0; 125 count = 0; 126 } 127 128 /** 129 * Create a <tt>MemoryHandler</tt>. 130 * <p> 131 * The <tt>MemoryHandler</tt> is configured based on <tt>LogManager</tt> 132 * properties (or their default values) except that the given <tt>pushLevel</tt> 133 * argument and buffer size argument are used. 134 * 135 * @param target the Handler to which to publish output. 136 * @param size the number of log records to buffer (must be greater than zero) 137 * @param pushLevel message level to push on 138 * 139 * @throws IllegalArgumentException if size is <= 0 140 */ 141 public MemoryHandler(Handler target, int size, Level pushLevel) { 142 if (target == null || pushLevel == null) { 143 throw new NullPointerException(); 144 } 145 if (size <= 0) { 146 throw new IllegalArgumentException(); 147 } 148 sealed = false; 149 configure(); 150 sealed = true; 151 this.target = target; 152 this.pushLevel = pushLevel; 153 this.size = size; 154 init(); 155 } 156 157 /** 158 * Store a <tt>LogRecord</tt> in an internal buffer. 159 * <p> 160 * If there is a <tt>Filter</tt>, its <tt>isLoggable</tt> 161 * method is called to check if the given log record is loggable. 162 * If not we return. Otherwise the given record is copied into 163 * an internal circular buffer. Then the record's level property is 164 * compared with the <tt>pushLevel</tt>. If the given level is 165 * greater than or equal to the <tt>pushLevel</tt> then <tt>push</tt> 166 * is called to write all buffered records to the target output 167 * <tt>Handler</tt>. 168 * 169 * @param record description of the log event. A null record is 170 * silently ignored and is not published 171 */ 172 public synchronized void publish(LogRecord record) { 173 if (!isLoggable(record)) { 174 return; 175 } 176 int ix = (start+count)%buffer.length; 177 buffer[ix] = record; 178 if (count < buffer.length) { 179 count++; 180 } else { 181 start++; 182 start %= buffer.length; 183 } 184 if (record.getLevel().intValue() >= pushLevel.intValue()) { 185 push(); 186 } 187 } 188 189 /** 190 * Push any buffered output to the target <tt>Handler</tt>. 191 * <p> 192 * The buffer is then cleared. 193 */ 194 public synchronized void push() { 195 for (int i = 0; i < count; i++) { 196 int ix = (start+i)%buffer.length; 197 LogRecord record = buffer[ix]; 198 target.publish(record); 199 } 200 // Empty the buffer. 201 start = 0; 202 count = 0; 203 } 204 205 /** 206 * Causes a flush on the target <tt>Handler</tt>. 207 * <p> 208 * Note that the current contents of the <tt>MemoryHandler</tt> 209 * buffer are <b>not</b> written out. That requires a "push". 210 */ 211 public void flush() { 212 target.flush(); 213 } 214 215 /** 216 * Close the <tt>Handler</tt> and free all associated resources. 217 * This will also close the target <tt>Handler</tt>. 218 * 219 * @exception SecurityException if a security manager exists and if 220 * the caller does not have <tt>LoggingPermission("control")</tt>. 221 */ 222 public void close() throws SecurityException { 223 target.close(); 224 setLevel(Level.OFF); 225 } 226 227 /** 228 * Set the <tt>pushLevel</tt>. After a <tt>LogRecord</tt> is copied 229 * into our internal buffer, if its level is greater than or equal to 230 * the <tt>pushLevel</tt>, then <tt>push</tt> will be called. 231 * 232 * @param newLevel the new value of the <tt>pushLevel</tt> 233 * @exception SecurityException if a security manager exists and if 234 * the caller does not have <tt>LoggingPermission("control")</tt>. 235 */ 236 public void setPushLevel(Level newLevel) throws SecurityException { 237 if (newLevel == null) { 238 throw new NullPointerException(); 239 } 240 LogManager manager = LogManager.getLogManager(); 241 checkPermission(); 242 pushLevel = newLevel; 243 } 244 245 /** 246 * Get the <tt>pushLevel</tt>. 247 * 248 * @return the value of the <tt>pushLevel</tt> 249 */ 250 public synchronized Level getPushLevel() { 251 return pushLevel; 252 } 253 254 /** 255 * Check if this <tt>Handler</tt> would actually log a given 256 * <tt>LogRecord</tt> into its internal buffer. 257 * <p> 258 * This method checks if the <tt>LogRecord</tt> has an appropriate level and 259 * whether it satisfies any <tt>Filter</tt>. However it does <b>not</b> 260 * check whether the <tt>LogRecord</tt> would result in a "push" of the 261 * buffer contents. It will return false if the <tt>LogRecord</tt> is null. 262 * <p> 263 * @param record a <tt>LogRecord</tt> 264 * @return true if the <tt>LogRecord</tt> would be logged. 265 * 266 */ 267 public boolean isLoggable(LogRecord record) { 268 return super.isLoggable(record); 269 } 270} 271