Introduce a verbose mode for the Java agent

[deliverable/lttng-ust.git] / liblttng-ust-java-agent / java / lttng-ust-agent-common / org / lttng / ust / agent / utils / LttngUstAgentLogger.java

diff --git a/liblttng-ust-java-agent/java/lttng-ust-agent-common/org/lttng/ust/agent/utils/LttngUstAgentLogger.java b/liblttng-ust-java-agent/java/lttng-ust-agent-common/org/lttng/ust/agent/utils/LttngUstAgentLogger.java
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+++ b/liblttng-ust-java-agent/java/lttng-ust-agent-common/org/lttng/ust/agent/utils/LttngUstAgentLogger.java
@@ -0,0 +1,46 @@
+/*
+ * Copyright (C) 2016 - EfficiOS Inc., Alexandre Montplaisir <alexmonthy@efficios.com>
+ *
+ * This library is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License, version 2.1 only,
+ * as published by the Free Software Foundation.
+ *
+ * This library is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
+ * for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+package org.lttng.ust.agent.utils;
+
+/**
+ * Logging infrastructure for the lttng-ust Java agent. It prints log messages
+ * to stderr but only when the environment variable LTTNG_UST_DEBUG is defined.
+ *
+ * @author Alexandre Montplaisir
+ */
+public class LttngUstAgentLogger {
+
+       private static final String ENV_VAR_NAME = "LTTNG_UST_DEBUG";
+       private static final boolean LOGGING_ENABLED = (System.getenv(ENV_VAR_NAME) == null ? false : true);
+
+       /**
+        * Log event. Will be printed to stderr if the environment variable
+        * "LTTNG_UST_DEBUG" is defined.
+        *
+        * @param c
+        *            The class logging the message (should normally be called with
+        *            {@link #getClass()}).
+        * @param message
+        *            The message to print
+        */
+       public static void log(Class<?> c, String message) {
+               if (LOGGING_ENABLED) {
+                       System.err.println(c.getSimpleName() + ": " + message);
+               }
+       }
+}