Fix event overflow

- Fixes #89
- Added new method into EnsembleListeger which can
  be used to listen ensemble errors.

spring-statemachine-core/src/main/java/org/springframework/statemachine/ensemble/CompositeEnsembleListener.java

@@ -56,4 +56,12 @@ public class CompositeEnsembleListener<S, E> extends AbstractCompositeListener<E
 		}
 	}
 
+	@Override
+	public void ensembleError(StateMachineEnsembleException exception) {
+		for (Iterator<EnsembleListeger<S, E>> iterator = getListeners().reverse(); iterator.hasNext();) {
+			EnsembleListeger<S, E> listener = iterator.next();
+			listener.ensembleError(exception);
+		}
+	}
+
 }

spring-statemachine-core/src/main/java/org/springframework/statemachine/ensemble/DistributedStateMachine.java

@@ -202,9 +202,9 @@ public class DistributedStateMachine<S, E> extends LifecycleObjectSupport implem
 					&& stateContext.getTransition().getKind() == TransitionKind.INTERNAL
 					&& ObjectUtils.nullSafeEquals(delegate.getId(),
 							stateContext.getMessageHeader(StateMachineSystemConstants.STATEMACHINE_IDENTIFIER))) {
-				StateMachineContext<S, E> xxx = ensemble.getState();
+				StateMachineContext<S, E> current = ensemble.getState();
 				ensemble.setState(new DefaultStateMachineContext<S, E>(
-						xxx.getState(), stateContext.getEvent(), stateContext
+						current.getState(), stateContext.getEvent(), stateContext
 								.getMessageHeaders(), stateContext.getStateMachine().getExtendedState()));
 			}
 			return stateContext;
@@ -262,6 +262,14 @@ public class DistributedStateMachine<S, E> extends LifecycleObjectSupport implem
 			}
 		}
 
+		@Override
+		public void ensembleError(StateMachineEnsembleException exception) {
+			// TODO: when we get support for sm error handling,
+			//       propagate this exception there
+			log.error("Ensemble error", exception);
+			throw exception;
+		}
+
 	}
 
 }

spring-statemachine-core/src/main/java/org/springframework/statemachine/ensemble/EnsembleListeger.java

@@ -51,4 +51,11 @@ public interface EnsembleListeger<S, E> {
 	 */
 	void stateChanged(StateMachineContext<S, E> context);
 
+	/**
+	 * Called when {@link StateMachineEnsemble} resulted an error.
+	 *
+	 * @param exception the exception
+	 */
+	void ensembleError(StateMachineEnsembleException exception);
+
 }

spring-statemachine-core/src/main/java/org/springframework/statemachine/ensemble/StateMachineEnsembleException.java

@@ -0,0 +1,70 @@
+/*
+ * Copyright 2015 the original author or authors.
+ *
+ * Licensed 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.springframework.statemachine.ensemble;
+
+import java.io.IOException;
+
+import org.springframework.statemachine.StateMachineException;
+
+/**
+ * General exception indicating a problem in ensemble.
+ *
+ * @author Janne Valkealahti
+ *
+ */
+public class StateMachineEnsembleException extends StateMachineException {
+
+	private static final long serialVersionUID = 960498044587123343L;
+
+	/**
+	 * Instantiates a new state machine ensemble exception.
+	 *
+	 * @param e the e
+	 */
+	public StateMachineEnsembleException(IOException e) {
+		super(e);
+	}
+
+	/**
+	 * Instantiates a new state machine ensemble exception.
+	 *
+	 * @param message the message
+	 * @param e the e
+	 */
+	public StateMachineEnsembleException(String message, Exception e) {
+		super(message, e);
+	}
+
+	/**
+	 * Instantiates a new state machine ensemble exception.
+	 *
+	 * @param message the message
+	 * @param cause the cause
+	 */
+	public StateMachineEnsembleException(String message, Throwable cause) {
+		super(message, cause);
+	}
+
+	/**
+	 * Instantiates a new state machine ensemble exception.
+	 *
+	 * @param message the message
+	 */
+	public StateMachineEnsembleException(String message) {
+		super(message);
+	}
+
+}

spring-statemachine-core/src/main/java/org/springframework/statemachine/ensemble/StateMachineEnsembleObjectSupport.java

@@ -59,6 +59,10 @@ public abstract class StateMachineEnsembleObjectSupport<S, E> extends LifecycleO
 		ensembleListener.stateMachineLeft(stateMachine, context);
 	}
 
+	protected void notifyError(StateMachineEnsembleException exception) {
+		ensembleListener.ensembleError(exception);
+	}
+
 	protected void notifyStateChanged(StateMachineContext<S, E> context) {
 		if (log.isTraceEnabled()) {
 			log.trace("Notify notifyStateChanged " + context);