Add a Log4j 2.x Java agent

[lttng-ust.git] / doc / examples / java-log4j / HelloLog4j.java

diff --git a/doc/examples/java-log4j/HelloLog4j.java b/doc/examples/java-log4j/HelloLog4j.java
new file mode 100644 (file)
index 0000000..11c96ab
--- /dev/null
+++ b/doc/examples/java-log4j/HelloLog4j.java
@@ -0,0 +1,89 @@
+/*
+ * SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2015 EfficiOS Inc.
+ * Copyright (C) 2015 Alexandre Montplaisir <alexmonthy@efficios.com>
+ * Copyright (C) 2014 Christian Babeux <christian.babeux@efficios.com>
+ */
+
+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 HelloLog4j {
+
+       private static final Logger HELLO_LOG = Logger.getLogger(HelloLog4j.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();
+       }
+}