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
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 * <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 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 sealed = false;
120 configure();
121 sealed = true;
122
123 LogManager manager = LogManager.getLogManager();
124 String handlerName = getClass().getName();
125 String targetName = manager.getProperty(handlerName+".target");
126 if (targetName == null) {
127 throw new RuntimeException("The handler " + handlerName
128 + " does not specify a target");
129 }
130 Class<?> clz;
131 try {
132 clz = ClassLoader.getSystemClassLoader().loadClass(targetName);
133 target = (Handler) clz.newInstance();
134 } catch (ClassNotFoundException | InstantiationException | IllegalAccessException e) {
135 throw new RuntimeException("MemoryHandler can't load handler target \"" + targetName + "\"" , e);
136 }
137 init();
138 }
139
140 // Initialize. Size is a count of LogRecords.
141 private void init() {
142 buffer = new LogRecord[size];
143 start = 0;
144 count = 0;
145 }
146
147 /**
148 * Create a <tt>MemoryHandler</tt>.
149 * <p>
150 * The <tt>MemoryHandler</tt> is configured based on <tt>LogManager</tt>
151 * properties (or their default values) except that the given <tt>pushLevel</tt>
152 * argument and buffer size argument are used.
153 *
154 * @param target the Handler to which to publish output.
155 * @param size the number of log records to buffer (must be greater than zero)
156 * @param pushLevel message level to push on
157 *
158 * @throws IllegalArgumentException if size is <= 0
159 */
160 public MemoryHandler(Handler target, int size, Level pushLevel) {
161 if (target == null || pushLevel == null) {
162 throw new NullPointerException();
163 }
164 if (size <= 0) {
165 throw new IllegalArgumentException();
166 }
167 sealed = false;
168 configure();
169 sealed = true;
170 this.target = target;
171 this.pushLevel = pushLevel;
172 this.size = size;
173 init();
174 }
175
176 /**
177 * Store a <tt>LogRecord</tt> in an internal buffer.
178 * <p>
179 * If there is a <tt>Filter</tt>, its <tt>isLoggable</tt>
180 * method is called to check if the given log record is loggable.
181 * If not we return. Otherwise the given record is copied into
182 * an internal circular buffer. Then the record's level property is
183 * compared with the <tt>pushLevel</tt>. If the given level is
184 * greater than or equal to the <tt>pushLevel</tt> then <tt>push</tt>
185 * is called to write all buffered records to the target output
186 * <tt>Handler</tt>.
187 *
188 * @param record description of the log event. A null record is
189 * silently ignored and is not published
190 */
191 public synchronized void publish(LogRecord record) {
192 if (!isLoggable(record)) {
193 return;
194 }
195 int ix = (start+count)%buffer.length;
196 buffer[ix] = record;
197 if (count < buffer.length) {
198 count++;
199 } else {
200 start++;
201 start %= buffer.length;
202 }
203 if (record.getLevel().intValue() >= pushLevel.intValue()) {
204 push();
205 }
206 }
207
208 /**
209 * Push any buffered output to the target <tt>Handler</tt>.
210 * <p>
211 * The buffer is then cleared.
212 */
213 public synchronized void push() {
214 for (int i = 0; i < count; i++) {
215 int ix = (start+i)%buffer.length;
216 LogRecord record = buffer[ix];
217 target.publish(record);
218 }
219 // Empty the buffer.
220 start = 0;
221 count = 0;
222 }
223
224 /**
225 * Causes a flush on the target <tt>Handler</tt>.
226 * <p>
227 * Note that the current contents of the <tt>MemoryHandler</tt>
228 * buffer are <b>not</b> written out. That requires a "push".
229 */
230 public void flush() {
231 target.flush();
232 }
233
234 /**
235 * Close the <tt>Handler</tt> and free all associated resources.
236 * This will also close the target <tt>Handler</tt>.
237 *
238 * @exception SecurityException if a security manager exists and if
239 * the caller does not have <tt>LoggingPermission("control")</tt>.
240 */
241 public void close() throws SecurityException {
242 target.close();
243 setLevel(Level.OFF);
244 }
245
246 /**
247 * Set the <tt>pushLevel</tt>. After a <tt>LogRecord</tt> is copied
248 * into our internal buffer, if its level is greater than or equal to
249 * the <tt>pushLevel</tt>, then <tt>push</tt> will be called.
250 *
251 * @param newLevel the new value of the <tt>pushLevel</tt>
252 * @exception SecurityException if a security manager exists and if
253 * the caller does not have <tt>LoggingPermission("control")</tt>.
254 */
255 public void setPushLevel(Level newLevel) throws SecurityException {
256 if (newLevel == null) {
257 throw new NullPointerException();
258 }
259 LogManager manager = LogManager.getLogManager();
260 checkPermission();
261 pushLevel = newLevel;
262 }
263
264 /**
265 * Get the <tt>pushLevel</tt>.
266 *
267 * @return the value of the <tt>pushLevel</tt>
268 */
269 public synchronized Level getPushLevel() {
270 return pushLevel;
271 }
272
273 /**
274 * Check if this <tt>Handler</tt> would actually log a given
275 * <tt>LogRecord</tt> into its internal buffer.
276 * <p>
277 * This method checks if the <tt>LogRecord</tt> has an appropriate level and
278 * whether it satisfies any <tt>Filter</tt>. However it does <b>not</b>
279 * check whether the <tt>LogRecord</tt> would result in a "push" of the
280 * buffer contents. It will return false if the <tt>LogRecord</tt> is null.
281 * <p>
282 * @param record a <tt>LogRecord</tt>
283 * @return true if the <tt>LogRecord</tt> would be logged.
284 *
285 */
286 public boolean isLoggable(LogRecord record) {
287 return super.isLoggable(record);
288 }
289 }