1 /*
2 * Copyright (c) 2000, 2012, 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
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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 * <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>. </li>
43 * <li>
44 * An external class calls the <tt>push</tt> method explicitly. </li>
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. </li>
49 * </ul>
50 * <p>
51 * <b>Configuration:</b>
52 * By default each <tt>MemoryHandler</tt> is initialized using the following
53 * <tt>LogManager</tt> configuration properties where <tt><handler-name></tt>
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 <tt>Handler</tt>
61 * (defaults to <tt>Level.ALL</tt>). </li>
62 * <li> <handler-name>.filter
63 * specifies the name of a <tt>Filter</tt> class to use
64 * (defaults to no <tt>Filter</tt>). </li>
65 * <li> <handler-name>.size
66 * defines the buffer size (defaults to 1000). </li>
67 * <li> <handler-name>.push
68 * defines the <tt>pushLevel</tt> (defaults to <tt>level.SEVERE</tt>). </li>
69 * <li> <handler-name>.target
70 * specifies the name of the target <tt>Handler </tt> 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 * <p>
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 // Private method to configure a MemoryHandler from LogManager
98 // properties and/or default values as specified in the class
99 // javadoc.
100 private void configure() {
101 LogManager manager = LogManager.getLogManager();
102 String cname = getClass().getName();
103
104 pushLevel = manager.getLevelProperty(cname +".push", Level.SEVERE);
105 size = manager.getIntProperty(cname + ".size", DEFAULT_SIZE);
106 if (size <= 0) {
107 size = DEFAULT_SIZE;
108 }
109 setLevel(manager.getLevelProperty(cname +".level", Level.ALL));
110 setFilter(manager.getFilterProperty(cname +".filter", null));
111 setFormatter(manager.getFormatterProperty(cname +".formatter", new SimpleFormatter()));
112 }
113
114 /**
115 * Create a <tt>MemoryHandler</tt> and configure it based on
116 * <tt>LogManager</tt> configuration properties.
117 */
118 public MemoryHandler() {
119 doWithControlPermission(this::configure);
120
121 LogManager manager = LogManager.getLogManager();
122 String handlerName = getClass().getName();
123 String targetName = manager.getProperty(handlerName+".target");
124 if (targetName == null) {
125 throw new RuntimeException("The handler " + handlerName
126 + " does not specify a target");
127 }
128 Class<?> clz;
129 try {
130 clz = ClassLoader.getSystemClassLoader().loadClass(targetName);
131 target = (Handler) clz.newInstance();
132 } catch (ClassNotFoundException | InstantiationException | IllegalAccessException e) {
133 throw new RuntimeException("MemoryHandler can't load handler target \"" + targetName + "\"" , e);
134 }
135 init();
136 }
137
138 // Initialize. Size is a count of LogRecords.
139 private void init() {
140 buffer = new LogRecord[size];
141 start = 0;
142 count = 0;
143 }
144
145 /**
146 * Create a <tt>MemoryHandler</tt>.
147 * <p>
148 * The <tt>MemoryHandler</tt> is configured based on <tt>LogManager</tt>
149 * properties (or their default values) except that the given <tt>pushLevel</tt>
150 * argument and buffer size argument are used.
151 *
152 * @param target the Handler to which to publish output.
153 * @param size the number of log records to buffer (must be greater than zero)
154 * @param pushLevel message level to push on
155 *
156 * @throws IllegalArgumentException if {@code size is <= 0}
157 */
158 public MemoryHandler(Handler target, int size, Level pushLevel) {
159 if (target == null || pushLevel == null) {
160 throw new NullPointerException();
161 }
162 if (size <= 0) {
163 throw new IllegalArgumentException();
164 }
165 doWithControlPermission(this::configure);
166 this.target = target;
167 this.pushLevel = pushLevel;
168 this.size = size;
169 init();
170 }
171
172 /**
173 * Store a <tt>LogRecord</tt> in an internal buffer.
174 * <p>
175 * If there is a <tt>Filter</tt>, its <tt>isLoggable</tt>
176 * method is called to check if the given log record is loggable.
177 * If not we return. Otherwise the given record is copied into
178 * an internal circular buffer. Then the record's level property is
179 * compared with the <tt>pushLevel</tt>. If the given level is
180 * greater than or equal to the <tt>pushLevel</tt> then <tt>push</tt>
181 * is called to write all buffered records to the target output
182 * <tt>Handler</tt>.
183 *
184 * @param record description of the log event. A null record is
185 * silently ignored and is not published
186 */
187 @Override
188 public synchronized void publish(LogRecord record) {
189 if (!isLoggable(record)) {
190 return;
191 }
192 int ix = (start+count)%buffer.length;
193 buffer[ix] = record;
194 if (count < buffer.length) {
195 count++;
196 } else {
197 start++;
198 start %= buffer.length;
199 }
200 if (record.getLevel().intValue() >= pushLevel.intValue()) {
201 push();
202 }
203 }
204
205 /**
206 * Push any buffered output to the target <tt>Handler</tt>.
207 * <p>
208 * The buffer is then cleared.
209 */
210 public synchronized void push() {
211 for (int i = 0; i < count; i++) {
212 int ix = (start+i)%buffer.length;
213 LogRecord record = buffer[ix];
214 target.publish(record);
215 }
216 // Empty the buffer.
217 start = 0;
218 count = 0;
219 }
220
221 /**
222 * Causes a flush on the target <tt>Handler</tt>.
223 * <p>
224 * Note that the current contents of the <tt>MemoryHandler</tt>
225 * buffer are <b>not</b> written out. That requires a "push".
226 */
227 @Override
228 public void flush() {
229 target.flush();
230 }
231
232 /**
233 * Close the <tt>Handler</tt> and free all associated resources.
234 * This will also close the target <tt>Handler</tt>.
235 *
236 * @exception SecurityException if a security manager exists and if
237 * the caller does not have <tt>LoggingPermission("control")</tt>.
238 */
239 @Override
240 public void close() throws SecurityException {
241 target.close();
242 setLevel(Level.OFF);
243 }
244
245 /**
246 * Set the <tt>pushLevel</tt>. After a <tt>LogRecord</tt> is copied
247 * into our internal buffer, if its level is greater than or equal to
248 * the <tt>pushLevel</tt>, then <tt>push</tt> will be called.
249 *
250 * @param newLevel the new value of the <tt>pushLevel</tt>
251 * @exception SecurityException if a security manager exists and if
252 * the caller does not have <tt>LoggingPermission("control")</tt>.
253 */
254 public synchronized void setPushLevel(Level newLevel) throws SecurityException {
255 if (newLevel == null) {
256 throw new NullPointerException();
257 }
258 checkPermission();
259 pushLevel = newLevel;
260 }
261
262 /**
263 * Get the <tt>pushLevel</tt>.
264 *
265 * @return the value of the <tt>pushLevel</tt>
266 */
267 public Level getPushLevel() {
268 return pushLevel;
269 }
270
271 /**
272 * Check if this <tt>Handler</tt> would actually log a given
273 * <tt>LogRecord</tt> into its internal buffer.
274 * <p>
275 * This method checks if the <tt>LogRecord</tt> has an appropriate level and
276 * whether it satisfies any <tt>Filter</tt>. However it does <b>not</b>
277 * check whether the <tt>LogRecord</tt> would result in a "push" of the
278 * buffer contents. It will return false if the <tt>LogRecord</tt> is null.
279 * <p>
280 * @param record a <tt>LogRecord</tt>
281 * @return true if the <tt>LogRecord</tt> would be logged.
282 *
283 */
284 @Override
285 public boolean isLoggable(LogRecord record) {
286 return super.isLoggable(record);
287 }
288 }