fix: unix socket peercred on FreeBSD

[lttng-ust.git] / doc / examples / java-log4j / Hello.java

/*
 * Copyright (C) 2015 - EfficiOS Inc., Alexandre Montplaisir <alexmonthy@efficios.com>
 * Copyright (C) 2014 - Christian Babeux <christian.babeux@efficios.com>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to
 * deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

import java.io.IOException;

import org.apache.log4j.Appender;
import org.apache.log4j.BasicConfigurator;
import org.apache.log4j.Logger;
import org.apache.log4j.Level;
import org.lttng.ust.agent.log4j.LttngLogAppender;

/**
 * Example application using the LTTng-UST Java log4j agent.
 *
 * <p>
 * To obtain LTTng trace events, you should run the following sequence of
 * commands:
 * </p>
 *
 * <ul>
 * <li>$ lttng create</li>
 * <li>$ lttng enable-event -l -a</li>
 * <li>$ lttng start</li>
 * <li>(run this program)</li>
 * <li>$ lttng stop</li>
 * <li>$ lttng view</li>
 * <li>$ lttng destroy</li>
 * </ul>
 *
 * @author Alexandre Montplaisir
 * @author Christian Babeux
 */
public class Hello {

	private static final Logger HELLO_LOG = Logger.getLogger(Hello.class);

	/**
	 * Application start
	 *
	 * @param args
	 *            Command-line arguments
	 * @throws IOException
	 *             If the required native libraries cannot be found. You may
	 *             have to specify "-Djava.library.path=..." on the "java"
	 *             command line.
	 */
	public static void main(String args[]) throws IOException {

		/*
		 * Set lowest level to make sure all event levels are logged.
		 * Any jar can override the default log4j rootLogger level
		 * and a logger with no explicit level defaults to the non-null
		 * parent level. Events could be ignored if the inherited value
		 * is to low.
		 * e.g BSF  -> https://issues.apache.org/jira/browse/BSF-24
		 */
		HELLO_LOG.setLevel(Level.ALL);

		/* Start with the default Log4j configuration, which logs to console */
		BasicConfigurator.configure();

		/*
		 * Instantiate a LTTng log appender and attach it to the logger, which
		 * will now send the logged events to UST.
		 */
		Appender lttngAppender = new LttngLogAppender();
		HELLO_LOG.addAppender(lttngAppender);

		/*
		 * Here we've set up the appender programmatically, but it could also be
		 * defined at runtime, by reading a configuration file for example:
		 */
		// PropertyConfigurator.configure(fileName);

		/* Trigger some tracing events using the Log4j Logger created before. */
		HELLO_LOG.info("Hello World, the answer is " + 42);
		HELLO_LOG.info("Another info event");
		HELLO_LOG.error("An error event");

		/* Cleanup */
		HELLO_LOG.removeAppender(lttngAppender);
		lttngAppender.close();
	}
}