MemoryHandler.java revision 14360:03453120a011
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 26package 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 89public 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 @SuppressWarnings("deprecation") 121 Object o = clz.newInstance(); 122 target = (Handler) o; 123 } catch (ClassNotFoundException | InstantiationException | IllegalAccessException e) { 124 throw new RuntimeException("MemoryHandler can't load handler target \"" + targetName + "\"" , e); 125 } 126 init(); 127 } 128 129 // Initialize. Size is a count of LogRecords. 130 private void init() { 131 buffer = new LogRecord[size]; 132 start = 0; 133 count = 0; 134 } 135 136 /** 137 * Create a {@code MemoryHandler}. 138 * <p> 139 * The {@code MemoryHandler} is configured based on {@code LogManager} 140 * properties (or their default values) except that the given {@code pushLevel} 141 * argument and buffer size argument are used. 142 * 143 * @param target the Handler to which to publish output. 144 * @param size the number of log records to buffer (must be greater than zero) 145 * @param pushLevel message level to push on 146 * 147 * @throws IllegalArgumentException if {@code size is <= 0} 148 */ 149 public MemoryHandler(Handler target, int size, Level pushLevel) { 150 // configure with specific defaults for MemoryHandler 151 super(Level.ALL, new SimpleFormatter(), null); 152 153 if (target == null || pushLevel == null) { 154 throw new NullPointerException(); 155 } 156 if (size <= 0) { 157 throw new IllegalArgumentException(); 158 } 159 this.target = target; 160 this.pushLevel = pushLevel; 161 this.size = size; 162 init(); 163 } 164 165 /** 166 * Store a {@code LogRecord} in an internal buffer. 167 * <p> 168 * If there is a {@code Filter}, its {@code isLoggable} 169 * method is called to check if the given log record is loggable. 170 * If not we return. Otherwise the given record is copied into 171 * an internal circular buffer. Then the record's level property is 172 * compared with the {@code pushLevel}. If the given level is 173 * greater than or equal to the {@code pushLevel} then {@code push} 174 * is called to write all buffered records to the target output 175 * {@code Handler}. 176 * 177 * @param record description of the log event. A null record is 178 * silently ignored and is not published 179 */ 180 @Override 181 public synchronized void publish(LogRecord record) { 182 if (!isLoggable(record)) { 183 return; 184 } 185 int ix = (start+count)%buffer.length; 186 buffer[ix] = record; 187 if (count < buffer.length) { 188 count++; 189 } else { 190 start++; 191 start %= buffer.length; 192 } 193 if (record.getLevel().intValue() >= pushLevel.intValue()) { 194 push(); 195 } 196 } 197 198 /** 199 * Push any buffered output to the target {@code Handler}. 200 * <p> 201 * The buffer is then cleared. 202 */ 203 public synchronized void push() { 204 for (int i = 0; i < count; i++) { 205 int ix = (start+i)%buffer.length; 206 LogRecord record = buffer[ix]; 207 target.publish(record); 208 } 209 // Empty the buffer. 210 start = 0; 211 count = 0; 212 } 213 214 /** 215 * Causes a flush on the target {@code Handler}. 216 * <p> 217 * Note that the current contents of the {@code MemoryHandler} 218 * buffer are <b>not</b> written out. That requires a "push". 219 */ 220 @Override 221 public void flush() { 222 target.flush(); 223 } 224 225 /** 226 * Close the {@code Handler} and free all associated resources. 227 * This will also close the target {@code Handler}. 228 * 229 * @exception SecurityException if a security manager exists and if 230 * the caller does not have {@code LoggingPermission("control")}. 231 */ 232 @Override 233 public void close() throws SecurityException { 234 target.close(); 235 setLevel(Level.OFF); 236 } 237 238 /** 239 * Set the {@code pushLevel}. After a {@code LogRecord} is copied 240 * into our internal buffer, if its level is greater than or equal to 241 * the {@code pushLevel}, then {@code push} will be called. 242 * 243 * @param newLevel the new value of the {@code pushLevel} 244 * @exception SecurityException if a security manager exists and if 245 * the caller does not have {@code LoggingPermission("control")}. 246 */ 247 public synchronized void setPushLevel(Level newLevel) throws SecurityException { 248 if (newLevel == null) { 249 throw new NullPointerException(); 250 } 251 checkPermission(); 252 pushLevel = newLevel; 253 } 254 255 /** 256 * Get the {@code pushLevel}. 257 * 258 * @return the value of the {@code pushLevel} 259 */ 260 public Level getPushLevel() { 261 return pushLevel; 262 } 263 264 /** 265 * Check if this {@code Handler} would actually log a given 266 * {@code LogRecord} into its internal buffer. 267 * <p> 268 * This method checks if the {@code LogRecord} has an appropriate level and 269 * whether it satisfies any {@code Filter}. However it does <b>not</b> 270 * check whether the {@code LogRecord} would result in a "push" of the 271 * buffer contents. It will return false if the {@code LogRecord} is null. 272 * 273 * @param record a {@code LogRecord} 274 * @return true if the {@code LogRecord} would be logged. 275 * 276 */ 277 @Override 278 public boolean isLoggable(LogRecord record) { 279 return super.isLoggable(record); 280 } 281} 282