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
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7 * published by the Free Software Foundation. Oracle designates this
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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 *
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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 @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 }