Merge pull request #519 from kotslon/spring_config

fix creating processEngine with instance of ProcessEngineConfigurationIm...

modules/activiti-spring/src/main/java/org/activiti/spring/ProcessEngineFactoryBean.java

@@ -69,9 +69,11 @@ public class ProcessEngineFactoryBean implements FactoryBean<ProcessEngine>, Dis
     }
 
     protected void configureExternallyManagedTransactions() {
-        SpringProcessEngineConfiguration engineConfiguration = (SpringProcessEngineConfiguration) processEngineConfiguration;
-        if (engineConfiguration.getTransactionManager() != null) {
-            processEngineConfiguration.setTransactionsExternallyManaged(true);
+        if (processEngineConfiguration instanceof SpringProcessEngineConfiguration) { // remark: any config can be injected, so we cannot have SpringConfiguration as member
+            SpringProcessEngineConfiguration engineConfiguration = (SpringProcessEngineConfiguration) processEngineConfiguration;
+            if (engineConfiguration.getTransactionManager() != null) {
+                processEngineConfiguration.setTransactionsExternallyManaged(true);
+            }
         }
     }