added better exception message if a dataSource is not provided

git-svn-id: https://svn.apache.org/repos/asf/incubator/activemq/trunk@412076 13f79535-47bb-0310-9956-ffa450edef68

activemq-core/src/main/java/org/apache/activemq/store/jdbc/JDBCPersistenceAdapter.java

@@ -290,6 +290,9 @@ public class JDBCPersistenceAdapter implements PersistenceAdapter {
     }
 
     public TransactionContext getTransactionContext() {
+        if (dataSource == null) { 
+            throw new IllegalArgumentException("No dataSource property has been configured");
+        }
         return new TransactionContext(dataSource);
     }