Add a Log4j 2.x Java agent

[lttng-ust.git] / doc / examples / java-log4j2-ctx / HelloLog4j2Ctx.java

diff --git a/doc/examples/java-log4j2-ctx/HelloLog4j2Ctx.java b/doc/examples/java-log4j2-ctx/HelloLog4j2Ctx.java
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+/*
+ * SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2022 EfficiOS Inc.
+ */
+
+import java.net.URI;
+import java.util.ArrayList;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.apache.logging.log4j.core.LoggerContext;
+
+/**
+ * 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>
+ *
+ */
+public class HelloLog4j2Ctx {
+
+       /**
+        * Application start
+        *
+        * @param args Command-line arguments
+        */
+       public static void main(String args[]) {
+
+               URI configFileUri1 = URI.create("./log4j2.ctx1.xml");
+               URI configFileUri2 = URI.create("./log4j2.ctx2.xml");
+
+               LoggerContext loggerContext1 = (LoggerContext) LogManager.getContext(ClassLoader.getSystemClassLoader(), false,
+                               configFileUri1);
+               LoggerContext loggerContext2 = (LoggerContext) LogManager.getContext(ClassLoader.getSystemClassLoader(), false,
+                               configFileUri2);
+
+               /* Loggers in different contexts with the same name. */
+               Logger logger1ctx1 = loggerContext1.getLogger(HelloLog4j2Ctx.class);
+               Logger logger1ctx2 = loggerContext2.getLogger(HelloLog4j2Ctx.class);
+
+               Logger logger2ctx1 = loggerContext1.getLogger("Logger2");
+               Logger logger3ctx2 = loggerContext2.getLogger("Logger3");
+
+               ArrayList<Logger> loggers = new ArrayList<Logger>();
+
+               loggers.add(logger1ctx1);
+               loggers.add(logger1ctx2);
+               loggers.add(logger2ctx1);
+               loggers.add(logger3ctx2);
+
+               for (Logger logger : loggers) {
+                       /* Trigger some tracing events using the Log4j Logger created before. */
+                       logger.info("Context config: Hello World, the answer is " + 42);
+                       logger.info("Context config: Another info event");
+                       logger.error("Context config: An error event");
+               }
+       }
+}