Add way to remove listener

- Change Region interface and underlying listener
  classes so that we can unregister registered
  listeners.

spring-statemachine-core/src/main/java/org/springframework/statemachine/listener/AbstractCompositeListener.java

@@ -55,6 +55,15 @@ public class AbstractCompositeListener<T> {
 		listeners.add(listener);
 	}
 
+	/**
+	 * Unregister a listener.
+	 *
+	 * @param listener the listener
+	 */
+	public void unregister(T listener) {
+		listeners.remove(listener);
+	}
+
 	/**
 	 * Gets the listeners.
 	 *

spring-statemachine-core/src/main/java/org/springframework/statemachine/listener/OrderedComposite.java

@@ -82,6 +82,20 @@ public class OrderedComposite<S> {
 		list.addAll(unordered);
 	}
 
+	/**
+	 * Unregister item.
+	 *
+	 * @param item item
+	 */
+	public void remove(S item) {
+		ordered.remove(item);
+		unordered.remove(item);
+		Collections.sort(ordered, comparator);
+		list.clear();
+		list.addAll(ordered);
+		list.addAll(unordered);
+	}
+
 	/**
 	 * Public getter for the list of items. The {@link Ordered} items come
 	 * first, followed by any unordered ones.

spring-statemachine-core/src/main/java/org/springframework/statemachine/region/Region.java

@@ -96,4 +96,11 @@ public interface Region<S, E> {
 	 */
 	void addStateListener(StateMachineListener<S, E> listener);
 
+	/**
+	 * Removes the state listener.
+	 *
+	 * @param listener the listener
+	 */
+	void removeStateListener(StateMachineListener<S, E> listener);
+
 }

spring-statemachine-core/src/main/java/org/springframework/statemachine/support/AbstractStateMachine.java

@@ -255,6 +255,11 @@ public abstract class AbstractStateMachine<S, E> extends StateMachineObjectSuppo
 		getStateListener().register(listener);
 	}
 
+	@Override
+	public void removeStateListener(StateMachineListener<S, E> listener) {
+		getStateListener().unregister(listener);
+	}
+
 	@Override
 	public boolean isComplete() {
 		if (currentState == null) {

spring-statemachine-core/src/test/java/org/springframework/statemachine/listener/CompositeStateMachineListenerTests.java

@@ -0,0 +1,49 @@
+/*
+ * 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.listener;
+
+import static org.hamcrest.Matchers.is;
+import static org.junit.Assert.assertThat;
+
+import java.util.List;
+
+import org.junit.Test;
+import org.springframework.statemachine.TestUtils;
+
+public class CompositeStateMachineListenerTests {
+
+	@Test
+	public void testRegister() throws Exception {
+		CompositeStateMachineListener<String, String> listener = new CompositeStateMachineListener<String, String>();
+		StateMachineListenerAdapter<String, String> adapter1 = new StateMachineListenerAdapter<String, String>();
+		listener.register(adapter1);
+		OrderedComposite<StateMachineListener<String, String>> listeners = listener.getListeners();
+		List<Object> list = TestUtils.readField("list", listeners);
+		assertThat(list.size(), is(1));
+	}
+
+	@Test
+	public void testUnregister() throws Exception {
+		CompositeStateMachineListener<String, String> listener = new CompositeStateMachineListener<String, String>();
+		StateMachineListenerAdapter<String, String> adapter1 = new StateMachineListenerAdapter<String, String>();
+		listener.register(adapter1);
+		listener.unregister(adapter1);
+		OrderedComposite<StateMachineListener<String, String>> listeners = listener.getListeners();
+		List<Object> list = TestUtils.readField("list", listeners);
+		assertThat(list.size(), is(0));
+	}
+
+}