1 /* 2 * Copyright (c) 2000, 2013, 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 26 package java.util.logging; 27 28 /** 29 * {@code Handler} that buffers requests in a circular buffer in memory. 30 * <p> 31 * Normally this {@code Handler} simply stores incoming {@code LogRecords} 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 {@code MemoryHandler} will push out its current buffer 35 * contents to a target {@code Handler}, 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 {@code LogRecord} has a type that is greater than 42 * a pre-defined level, the {@code pushLevel}. </li> 43 * <li> 44 * An external class calls the {@code push} method explicitly. </li> 45 * <li> 46 * A subclass overrides the {@code log} method and scans each incoming 47 * {@code LogRecord} and calls {@code push} if a record matches some 48 * desired criteria. </li> 49 * </ul> 50 * <p> 51 * <b>Configuration:</b> 52 * By default each {@code MemoryHandler} is initialized using the following 53 * {@code LogManager} configuration properties where {@code <handler-name>} 54 * refers to the fully-qualified class name of the handler. 55 * If properties are not defined 56 * (or have invalid values) then the specified default values are used. 57 * If no default value is defined then a RuntimeException is thrown. 58 * <ul> 59 * <li> <handler-name>.level 60 * specifies the level for the {@code Handler} 61 * (defaults to {@code Level.ALL}). </li> 62 * <li> <handler-name>.filter 63 * specifies the name of a {@code Filter} class to use 64 * (defaults to no {@code Filter}). </li> 65 * <li> <handler-name>.size 66 * defines the buffer size (defaults to 1000). </li> 67 * <li> <handler-name>.push 68 * defines the {@code pushLevel} (defaults to {@code level.SEVERE}). </li> 69 * <li> <handler-name>.target 70 * specifies the name of the target {@code Handler } class. 71 * (no default). </li> 72 * </ul> 73 * <p> 74 * For example, the properties for {@code MemoryHandler} would be: 75 * <ul> 76 * <li> java.util.logging.MemoryHandler.level=INFO </li> 77 * <li> java.util.logging.MemoryHandler.formatter=java.util.logging.SimpleFormatter </li> 78 * </ul> 79 * <p> 80 * For a custom handler, e.g. com.foo.MyHandler, the properties would be: 81 * <ul> 82 * <li> com.foo.MyHandler.level=INFO </li> 83 * <li> com.foo.MyHandler.formatter=java.util.logging.SimpleFormatter </li> 84 * </ul> 85 * 86 * @since 1.4 87 */ 88 89 public class MemoryHandler extends Handler { 90 private final static int DEFAULT_SIZE = 1000; 91 private volatile Level pushLevel; 92 private int size; 93 private Handler target; 94 private LogRecord buffer[]; 95 int start, count; 96 97 /** 98 * Create a {@code MemoryHandler} and configure it based on 99 * {@code LogManager} configuration properties. 100 */ 101 public MemoryHandler() { 102 // configure with specific defaults for MemoryHandler 103 super(Level.ALL, new SimpleFormatter(), null); 104 105 LogManager manager = LogManager.getLogManager(); 106 String cname = getClass().getName(); 107 pushLevel = manager.getLevelProperty(cname +".push", Level.SEVERE); 108 size = manager.getIntProperty(cname + ".size", DEFAULT_SIZE); 109 if (size <= 0) { 110 size = DEFAULT_SIZE; 111 } 112 String targetName = manager.getProperty(cname+".target"); 113 if (targetName == null) { 114 throw new RuntimeException("The handler " + cname 115 + " does not specify a target"); 116 } 117 Class<?> clz; 118 try { 119 clz = ClassLoader.getSystemClassLoader().loadClass(targetName); 120 target = (Handler) clz.newInstance(); 121 } catch (ClassNotFoundException | InstantiationException | IllegalAccessException e) { 122 throw new RuntimeException("MemoryHandler can't load handler target \"" + targetName + "\"" , e); 123 } 124 init(); 125 } 126 127 // Initialize. Size is a count of LogRecords. 128 private void init() { 129 buffer = new LogRecord[size]; 130 start = 0; 131 count = 0; 132 } 133 134 /** 135 * Create a {@code MemoryHandler}. 136 * <p> 137 * The {@code MemoryHandler} is configured based on {@code LogManager} 138 * properties (or their default values) except that the given {@code pushLevel} 139 * argument and buffer size argument are used. 140 * 141 * @param target the Handler to which to publish output. 142 * @param size the number of log records to buffer (must be greater than zero) 143 * @param pushLevel message level to push on 144 * 145 * @throws IllegalArgumentException if {@code size is <= 0} 146 */ 147 public MemoryHandler(Handler target, int size, Level pushLevel) { 148 // configure with specific defaults for MemoryHandler 149 super(Level.ALL, new SimpleFormatter(), null); 150 151 if (target == null || pushLevel == null) { 152 throw new NullPointerException(); 153 } 154 if (size <= 0) { 155 throw new IllegalArgumentException(); 156 } 157 this.target = target; 158 this.pushLevel = pushLevel; 159 this.size = size; 160 init(); 161 } 162 163 /** 164 * Store a {@code LogRecord} in an internal buffer. 165 * <p> 166 * If there is a {@code Filter}, its {@code isLoggable} 167 * method is called to check if the given log record is loggable. 168 * If not we return. Otherwise the given record is copied into 169 * an internal circular buffer. Then the record's level property is 170 * compared with the {@code pushLevel}. If the given level is 171 * greater than or equal to the {@code pushLevel} then {@code push} 172 * is called to write all buffered records to the target output 173 * {@code Handler}. 174 * 175 * @param record description of the log event. A null record is 176 * silently ignored and is not published 177 */ 178 @Override 179 public synchronized void publish(LogRecord record) { 180 if (!isLoggable(record)) { 181 return; 182 } 183 int ix = (start+count)%buffer.length; 184 buffer[ix] = record; 185 if (count < buffer.length) { 186 count++; 187 } else { 188 start++; 189 start %= buffer.length; 190 } 191 if (record.getLevel().intValue() >= pushLevel.intValue()) { 192 push(); 193 } 194 } 195 196 /** 197 * Push any buffered output to the target {@code Handler}. 198 * <p> 199 * The buffer is then cleared. 200 */ 201 public synchronized void push() { 202 for (int i = 0; i < count; i++) { 203 int ix = (start+i)%buffer.length; 204 LogRecord record = buffer[ix]; 205 target.publish(record); 206 } 207 // Empty the buffer. 208 start = 0; 209 count = 0; 210 } 211 212 /** 213 * Causes a flush on the target {@code Handler}. 214 * <p> 215 * Note that the current contents of the {@code MemoryHandler} 216 * buffer are <b>not</b> written out. That requires a "push". 217 */ 218 @Override 219 public void flush() { 220 target.flush(); 221 } 222 223 /** 224 * Close the {@code Handler} and free all associated resources. 225 * This will also close the target {@code Handler}. 226 * 227 * @exception SecurityException if a security manager exists and if 228 * the caller does not have {@code LoggingPermission("control")}. 229 */ 230 @Override 231 public void close() throws SecurityException { 232 target.close(); 233 setLevel(Level.OFF); 234 } 235 236 /** 237 * Set the {@code pushLevel}. After a {@code LogRecord} is copied 238 * into our internal buffer, if its level is greater than or equal to 239 * the {@code pushLevel}, then {@code push} will be called. 240 * 241 * @param newLevel the new value of the {@code pushLevel} 242 * @exception SecurityException if a security manager exists and if 243 * the caller does not have {@code LoggingPermission("control")}. 244 */ 245 public synchronized void setPushLevel(Level newLevel) throws SecurityException { 246 if (newLevel == null) { 247 throw new NullPointerException(); 248 } 249 checkPermission(); 250 pushLevel = newLevel; 251 } 252 253 /** 254 * Get the {@code pushLevel}. 255 * 256 * @return the value of the {@code pushLevel} 257 */ 258 public Level getPushLevel() { 259 return pushLevel; 260 } 261 262 /** 263 * Check if this {@code Handler} would actually log a given 264 * {@code LogRecord} into its internal buffer. 265 * <p> 266 * This method checks if the {@code LogRecord} has an appropriate level and 267 * whether it satisfies any {@code Filter}. However it does <b>not</b> 268 * check whether the {@code LogRecord} would result in a "push" of the 269 * buffer contents. It will return false if the {@code LogRecord} is null. 270 * 271 * @param record a {@code LogRecord} 272 * @return true if the {@code LogRecord} would be logged. 273 * 274 */ 275 @Override 276 public boolean isLoggable(LogRecord record) { 277 return super.isLoggable(record); 278 } 279 }