doc/examples/java-jul/Hello.java

   1 /*
   2  * SPDX-License-Identifier: MIT
   3  *
   4  * Copyright (C) 2015 EfficiOS Inc., Alexandre Montplaisir <alexmonthy@efficios.com>
   5  * Copyright (C) 2013 David Goulet <dgoulet@efficios.com>
   6  */
   7
   8 import java.io.IOException;
   9 import java.util.logging.Handler;
  10 import java.util.logging.Logger;
  11
  12 import org.lttng.ust.agent.jul.LttngLogHandler;
  13
  14 /**
  15  * Example application using the LTTng-UST Java JUL agent.
  16  *
  17  * <p>
  18  * Basically all that is required is to instantiate a {@link LttngLogHandler}
  19  * and to attach it to a JUL {@link Logger}. Then use the Logger normally to log
  20  * messages, which will be sent to UST as trace events.
  21  * <p>
  22  * </p>
  23  * {@link Logger} names are used as event names on the UST side. This means that
  24  * by enabling/disabling certain events in the tracing session, you are
  25  * effectively enabling and disabling Loggers on the Java side. Note that this
  26  * applies only to {@link LttngLogHandler}'s. If other handlers are attached to
  27  * the Logger, those will continue logging events normally.
  28  * </p>
  29  *
  30  * <p>
  31  * To obtain LTTng trace events, you should run the following sequence of
  32  * commands:
  33  * </p>
  34  *
  35  * <ul>
  36  * <li>$ lttng create</li>
  37  * <li>$ lttng enable-event -j -a</li>
  38  * <li>$ lttng start</li>
  39  * <li>(run this program)</li>
  40  * <li>$ lttng stop</li>
  41  * <li>$ lttng view</li>
  42  * <li>$ lttng destroy</li>
  43  * </ul>
  44  *
  45  * @author Alexandre Montplaisir
  46  * @author David Goulet
  47  */
  48 public class Hello {
  49
  50         /** Class-wide JUL logger object */
  51         private static final Logger LOGGER = Logger.getLogger(Hello.class.getName());
  52
  53         /**
  54          * Application start
  55          *
  56          * @param args
  57          *            Command-line arguments
  58          * @throws IOException
  59          *             If the required native libraries cannot be found. You may
  60          *             have to specify "-Djava.library.path=..." on the "java"
  61          *             command line.
  62          */
  63         public static void main(String args[]) throws IOException {
  64
  65                 /* Instantiate a LTTngLogHandler object, and attach it to our logger */
  66                 Handler lttngHandler = new LttngLogHandler();
  67                 LOGGER.addHandler(lttngHandler);
  68
  69                 /* Log events using the JUL Logger created before. */
  70                 LOGGER.info("Hello World, the answer is " + 42);
  71                 LOGGER.info("Another info event");
  72                 LOGGER.severe("A severe event");
  73
  74                 /* Cleanup */
  75                 LOGGER.removeHandler(lttngHandler);
  76                 lttngHandler.close();
  77         }
  78 }