doc/examples/java-log4j/Hello.java

   1 /*
   2  * SPDX-License-Identifier: MIT
   3  *
   4  * Copyright (C) 2015 EfficiOS Inc.
   5  * Copyright (C) 2015 Alexandre Montplaisir <alexmonthy@efficios.com>
   6  * Copyright (C) 2014 Christian Babeux <christian.babeux@efficios.com>
   7  */
   8
   9 import java.io.IOException;
  10
  11 import org.apache.log4j.Appender;
  12 import org.apache.log4j.BasicConfigurator;
  13 import org.apache.log4j.Logger;
  14 import org.apache.log4j.Level;
  15 import org.lttng.ust.agent.log4j.LttngLogAppender;
  16
  17 /**
  18  * Example application using the LTTng-UST Java log4j agent.
  19  *
  20  * <p>
  21  * To obtain LTTng trace events, you should run the following sequence of
  22  * commands:
  23  * </p>
  24  *
  25  * <ul>
  26  * <li>$ lttng create</li>
  27  * <li>$ lttng enable-event -l -a</li>
  28  * <li>$ lttng start</li>
  29  * <li>(run this program)</li>
  30  * <li>$ lttng stop</li>
  31  * <li>$ lttng view</li>
  32  * <li>$ lttng destroy</li>
  33  * </ul>
  34  *
  35  * @author Alexandre Montplaisir
  36  * @author Christian Babeux
  37  */
  38 public class Hello {
  39
  40         private static final Logger HELLO_LOG = Logger.getLogger(Hello.class);
  41
  42         /**
  43          * Application start
  44          *
  45          * @param args
  46          *            Command-line arguments
  47          * @throws IOException
  48          *             If the required native libraries cannot be found. You may
  49          *             have to specify "-Djava.library.path=..." on the "java"
  50          *             command line.
  51          */
  52         public static void main(String args[]) throws IOException {
  53
  54                 /*
  55                  * Set lowest level to make sure all event levels are logged.
  56                  * Any jar can override the default log4j rootLogger level
  57                  * and a logger with no explicit level defaults to the non-null
  58                  * parent level. Events could be ignored if the inherited value
  59                  * is to low.
  60                  * e.g BSF  -> https://issues.apache.org/jira/browse/BSF-24
  61                  */
  62                 HELLO_LOG.setLevel(Level.ALL);
  63
  64                 /* Start with the default Log4j configuration, which logs to console */
  65                 BasicConfigurator.configure();
  66
  67                 /*
  68                  * Instantiate a LTTng log appender and attach it to the logger, which
  69                  * will now send the logged events to UST.
  70                  */
  71                 Appender lttngAppender = new LttngLogAppender();
  72                 HELLO_LOG.addAppender(lttngAppender);
  73
  74                 /*
  75                  * Here we've set up the appender programmatically, but it could also be
  76                  * defined at runtime, by reading a configuration file for example:
  77                  */
  78                 // PropertyConfigurator.configure(fileName);
  79
  80                 /* Trigger some tracing events using the Log4j Logger created before. */
  81                 HELLO_LOG.info("Hello World, the answer is " + 42);
  82                 HELLO_LOG.info("Another info event");
  83                 HELLO_LOG.error("An error event");
  84
  85                 /* Cleanup */
  86                 HELLO_LOG.removeAppender(lttngAppender);
  87                 lttngAppender.close();
  88         }
  89 }