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 * <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 *
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 <tt>MemoryHandler</tt> and configure it based on
99 * <tt>LogManager</tt> 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 <tt>MemoryHandler</tt>.
136 * <p>
137 * The <tt>MemoryHandler</tt> is configured based on <tt>LogManager</tt>
138 * properties (or their default values) except that the given <tt>pushLevel</tt>
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 <tt>LogRecord</tt> in an internal buffer.
165 * <p>
166 * If there is a <tt>Filter</tt>, its <tt>isLoggable</tt>
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 <tt>pushLevel</tt>. If the given level is
171 * greater than or equal to the <tt>pushLevel</tt> then <tt>push</tt>
172 * is called to write all buffered records to the target output
173 * <tt>Handler</tt>.
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 <tt>Handler</tt>.
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 <tt>Handler</tt>.
214 * <p>
215 * Note that the current contents of the <tt>MemoryHandler</tt>
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 <tt>Handler</tt> and free all associated resources.
225 * This will also close the target <tt>Handler</tt>.
226 *
227 * @exception SecurityException if a security manager exists and if
228 * the caller does not have <tt>LoggingPermission("control")</tt>.
229 */
230 @Override
231 public void close() throws SecurityException {
232 target.close();
233 setLevel(Level.OFF);
234 }
235
236 /**
237 * Set the <tt>pushLevel</tt>. After a <tt>LogRecord</tt> is copied
238 * into our internal buffer, if its level is greater than or equal to
239 * the <tt>pushLevel</tt>, then <tt>push</tt> will be called.
240 *
241 * @param newLevel the new value of the <tt>pushLevel</tt>
242 * @exception SecurityException if a security manager exists and if
243 * the caller does not have <tt>LoggingPermission("control")</tt>.
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 <tt>pushLevel</tt>.
255 *
256 * @return the value of the <tt>pushLevel</tt>
257 */
258 public Level getPushLevel() {
259 return pushLevel;
260 }
261
262 /**
263 * Check if this <tt>Handler</tt> would actually log a given
264 * <tt>LogRecord</tt> into its internal buffer.
265 * <p>
266 * This method checks if the <tt>LogRecord</tt> has an appropriate level and
267 * whether it satisfies any <tt>Filter</tt>. However it does <b>not</b>
268 * check whether the <tt>LogRecord</tt> would result in a "push" of the
269 * buffer contents. It will return false if the <tt>LogRecord</tt> is null.
270 *
271 * @param record a <tt>LogRecord</tt>
272 * @return true if the <tt>LogRecord</tt> would be logged.
273 *
274 */
275 @Override
276 public boolean isLoggable(LogRecord record) {
277 return super.isLoggable(record);
278 }
279 }