https://issues.apache.org/jira/browse/AMQ-3219 - adding missing MDCHelper class

git-svn-id: https://svn.apache.org/repos/asf/activemq/trunk@1082530 13f79535-47bb-0310-9956-ffa450edef68

activemq-core/src/main/java/org/apache/activemq/util/MDCHelper.java

@@ -0,0 +1,28 @@
+package org.apache.activemq.util;
+
+import org.slf4j.MDC;
+
+import java.util.Hashtable;
+import java.util.Map;
+
+/**
+ *  Helper class as MDC Log4J adapter doesn't behave well with null values
+ */
+public class MDCHelper {
+
+    public static Map getCopyOfContextMap() {
+        Map map = MDC.getCopyOfContextMap();
+        if (map == null) {
+            map = new Hashtable();
+        }
+        return map;
+    }
+
+    public static void setContextMap(Map map) {
+        if (map == null) {
+            map = new Hashtable();
+        }
+        MDC.setContextMap(map);
+    }
+
+}