Set TM as loaded only after a TM is located.

Previously the ServiceUtils component responsible for loading the
transaction manager would attempt to load a TM only once.  If it was not
found it would not try again.  This patch updates the ServiceUtils to
iterate over any TransactionManagerLocator implementations on the class
path and check each one util a TM is located.

activemq-service-extensions/src/main/java/org/apache/activemq/service/extensions/ActiveMQServiceExtensionLogger.java

@@ -0,0 +1,54 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.activemq.service.extensions;
+
+import org.jboss.logging.BasicLogger;
+import org.jboss.logging.Logger;
+import org.jboss.logging.annotations.LogMessage;
+import org.jboss.logging.annotations.Message;
+import org.jboss.logging.annotations.MessageLogger;
+
+/**
+ * @author mtaylor
+ *
+ * Logger Code 34
+ *
+ * each message id must be 6 digits long starting with 20, the 3rd digit donates the level so
+ *
+ * INF0  1
+ * WARN  2
+ * DEBUG 3
+ * ERROR 4
+ * TRACE 5
+ * FATAL 6
+ *
+ * so an INFO message would be 341000 to 341999
+ */
+
+@MessageLogger(projectCode = "AMQ")
+public interface ActiveMQServiceExtensionLogger extends BasicLogger
+{
+   /**
+    * The default logger.
+    */
+   ActiveMQServiceExtensionLogger LOGGER = Logger.getMessageLogger(ActiveMQServiceExtensionLogger.class, ActiveMQServiceExtensionLogger.class.getPackage().getName());
+
+   @LogMessage(level = Logger.Level.WARN)
+   @Message(id = 342000, value = "Attempted to locate a Transaction Manager but none found.", format = Message.Format.MESSAGE_FORMAT)
+   void transactionManagerNotFound();
+}

activemq-service-extensions/src/main/java/org/apache/activemq/service/extensions/ServiceUtils.java

@@ -58,12 +58,20 @@ public class ServiceUtils
       if (!transactionManagerLoaded)
       {
          Iterator<TransactionManagerLocator> it = ServiceLoader.load(TransactionManagerLocator.class).iterator();
-         if (it.hasNext())
+         while (it.hasNext() && transactionManager == null)
          {
             transactionManager = it.next().getTransactionManager();
          }
+
+         if (transactionManager != null)
+         {
             transactionManagerLoaded = true;
          }
+         else
+         {
+            ActiveMQServiceExtensionLogger.LOGGER.transactionManagerNotFound();
+         }
+      }
       return transactionManager;
    }