Add missing file

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

@@ -0,0 +1,72 @@
+/*
+ * 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 org.springframework.statemachine.StateMachine;
+import org.springframework.statemachine.StateMachineContext;
+
+/**
+ * {@code EnsembleListener} for various ensemble events.
+ *
+ * @author Janne Valkealahti
+ *
+ * @param <S> the type of state
+ * @param <E> the type of event
+ */
+public interface EnsembleListener<S, E> {
+
+	/**
+	 * Called when state machine joined an ensemble. This callback
+	 * is guaranteed to be called for a {@link StateMachine} who
+	 * requested a join. User of this listener should check that a
+	 * {@link StateMachine} is the one interested of. Implementation
+	 * may choose to notify other {@link StateMachine} joins if it is
+	 * able to do so. This may be called multiple time in case ensemble
+	 * has made a choice to leave machine due to ensemble errors.
+	 *
+	 * @param stateMachine the state machine
+	 * @param context the state machine context
+	 */
+	void stateMachineJoined(StateMachine<S, E> stateMachine, StateMachineContext<S, E> context);
+
+	/**
+	 * Called when state machine left an ensemble. This callback
+	 * is guaranteed to be called for a {@link StateMachine} who
+	 * requested a leave. User of this listener should check that a
+	 * {@link StateMachine} is the one interested of. Implementation
+	 * may choose to notify other {@link StateMachine} leaves if it is
+	 * able to do so.
+	 *
+	 * @param stateMachine the state machine
+	 * @param context the state machine context
+	 */
+	void stateMachineLeft(StateMachine<S, E> stateMachine, StateMachineContext<S, E> context);
+
+	/**
+	 * Called when ensemble is discovering a state change.
+	 *
+	 * @param context the state machine context
+	 */
+	void stateChanged(StateMachineContext<S, E> context);
+
+	/**
+	 * Called when {@link StateMachineEnsemble} resulted an error.
+	 *
+	 * @param exception the exception
+	 */
+	void ensembleError(StateMachineEnsembleException exception);
+
+}