2 * Copyright (C) 2013 - David Goulet <dgoulet@efficios.com>
4 * This library is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU Lesser General Public License, version 2.1 only,
6 * as published by the Free Software Foundation.
8 * This library is distributed in the hope that it will be useful, but WITHOUT
9 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
10 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
13 * You should have received a copy of the GNU Lesser General Public License
14 * along with this library; if not, write to the Free Software Foundation,
15 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
18 package org
.lttng
.ust
.agent
;
20 import java
.lang
.reflect
.Constructor
;
21 import java
.lang
.reflect
.Method
;
22 import java
.util
.logging
.Handler
;
23 import java
.util
.logging
.Logger
;
26 * The central agent managing the JUL and Log4j handlers.
28 * @author David Goulet
29 * @deprecated Applications are now expected to manage their Logger and Handler
33 public class LTTngAgent
{
35 private static LTTngAgent instance
= null;
38 * Public getter to acquire a reference to this singleton object.
40 * @return The agent instance
42 public static synchronized LTTngAgent
getLTTngAgent() {
43 if (instance
== null) {
44 instance
= new LTTngAgent();
50 * Dispose the agent. Applications should call this once they are done
53 public static synchronized void dispose() {
54 if (instance
!= null) {
55 instance
.disposeInstance();
61 private ILttngHandler julHandler
= null;
62 private ILttngHandler log4jAppender
= null;
65 * Private constructor. This is a singleton and a reference should be
66 * acquired using {@link #getLTTngAgent()}.
68 private LTTngAgent() {
74 * "Destructor" method.
76 private void disposeInstance() {
78 disposeLog4jAppender();
82 * Create a LTTng-JUL handler, and attach it to the JUL root logger.
84 private void initJulHandler() {
86 Class
<?
> julHandlerClass
= Class
.forName("org.lttng.ust.agent.jul.LttngLogHandler");
88 * It is safer to use Constructor.newInstance() rather than
89 * Class.newInstance(), because it will catch the exceptions thrown
90 * by the constructor below (which happens if the Java library is
91 * present, but the matching JNI one is not).
93 Constructor
<?
> julHandlerCtor
= julHandlerClass
.getConstructor();
94 julHandler
= (ILttngHandler
) julHandlerCtor
.newInstance();
96 /* Attach the handler to the root JUL logger */
97 Logger
.getLogger("").addHandler((Handler
) julHandler
);
98 } catch (ReflectiveOperationException e
) {
100 * LTTng JUL classes not found, no need to create the relevant
107 * Create a LTTng-logj4 appender, and attach it to the log4j root logger.
109 private void initLog4jAppender() {
111 * Since Log4j is a 3rd party library, we first need to check if we can
112 * load any of its classes.
114 if (!testLog4jClasses()) {
119 Class
<?
> log4jAppenderClass
= Class
.forName("org.lttng.ust.agent.log4j.LttngLogAppender");
120 Constructor
<?
> log4jAppendCtor
= log4jAppenderClass
.getConstructor();
121 log4jAppender
= (ILttngHandler
) log4jAppendCtor
.newInstance();
122 } catch (ReflectiveOperationException e
) {
124 * LTTng Log4j classes not found, no need to create the relevant
131 * Attach the appender to the root Log4j logger. Slightly more tricky
132 * here, as log4j.Logger is not in the base Java library, and we do not
133 * want the "common" package to depend on log4j. So we have to obtain it
134 * through reflection too.
137 Class
<?
> loggerClass
= Class
.forName("org.apache.log4j.Logger");
138 Class
<?
> appenderClass
= Class
.forName("org.apache.log4j.Appender");
140 Method getRootLoggerMethod
= loggerClass
.getMethod("getRootLogger", (Class
<?
>[]) null);
141 Method addAppenderMethod
= loggerClass
.getMethod("addAppender", appenderClass
);
143 Object rootLogger
= getRootLoggerMethod
.invoke(null, (Object
[]) null);
144 addAppenderMethod
.invoke(rootLogger
, log4jAppender
);
146 } catch (ReflectiveOperationException e
) {
148 * We have checked for the log4j library version previously, these
149 * classes should exist.
151 throw new IllegalStateException();
156 * Check if log4j >= 1.2.15 library is present.
158 private static boolean testLog4jClasses() {
159 Class
<?
> loggingEventClass
;
162 loggingEventClass
= Class
.forName("org.apache.log4j.spi.LoggingEvent");
163 } catch (ClassNotFoundException e
) {
165 * Log4j classes not found, no need to create the relevant objects
171 * Detect capabilities of the log4j library. We only support log4j >=
172 * 1.2.15. The getTimeStamp() method was introduced in log4j 1.2.15, so
173 * verify that it is available.
175 * We can't rely on the getPackage().getImplementationVersion() call
176 * that would retrieves information from the manifest file found in the
177 * JAR since the manifest file shipped from upstream is known to be
178 * broken in several versions of the library.
180 * More info: https://issues.apache.org/bugzilla/show_bug.cgi?id=44370
183 loggingEventClass
.getDeclaredMethod("getTimeStamp");
184 } catch (NoSuchMethodException e
) {
186 "Warning: The loaded log4j library is too old. Log4j tracing with LTTng will be disabled.");
188 } catch (SecurityException e
) {
196 * Detach the JUL handler from its logger and close it.
198 private void disposeJulHandler() {
199 if (julHandler
== null) {
200 /* The JUL handler was not activated, we have nothing to do */
203 Logger
.getLogger("").removeHandler((Handler
) julHandler
);
209 * Detach the log4j appender from its logger and close it.
211 private void disposeLog4jAppender() {
212 if (log4jAppender
== null) {
213 /* The log4j appender was not active, we have nothing to do */
218 * Detach the appender from the log4j root logger. Again, we have to do
219 * this via reflection.
222 Class
<?
> loggerClass
= Class
.forName("org.apache.log4j.Logger");
223 Class
<?
> appenderClass
= Class
.forName("org.apache.log4j.Appender");
225 Method getRootLoggerMethod
= loggerClass
.getMethod("getRootLogger", (Class
<?
>[]) null);
226 Method removeAppenderMethod
= loggerClass
.getMethod("removeAppender", appenderClass
);
228 Object rootLogger
= getRootLoggerMethod
.invoke(null, (Object
[]) null);
229 removeAppenderMethod
.invoke(rootLogger
, log4jAppender
);
231 } catch (ReflectiveOperationException e
) {
233 * We were able to attach the appender, we should not have problems
236 throw new IllegalStateException();
239 /* Close the appender */
240 log4jAppender
.close();
241 log4jAppender
= null;