INT-1040, added ResrWriteLock usage to the toString() and hashCode() methods, added Test

org.springframework.integration/src/main/java/org/springframework/integration/history/MessageHistory.java

@@ -30,8 +30,10 @@ import org.springframework.integration.support.ComponentMetadata;
  * Iterable list of {@link MessageHistoryEvent} instances.
  * 
  * @author Mark Fisher
+ * @author Oleg Zhurakousky
  * @since 2.0
  */
+@SuppressWarnings("serial")
 public class MessageHistory implements Iterable<MessageHistoryEvent>, Serializable {
 
 	private final List<MessageHistoryEvent> events = new ArrayList<MessageHistoryEvent>();
@@ -76,14 +78,26 @@ public class MessageHistory implements Iterable<MessageHistoryEvent>, Serializab
 	}
 
 	public int hashCode() {
-		return 17 * this.events.hashCode();
+		
+		try {
+			this.lock.readLock().lock();
+			return 17 * this.events.hashCode();
+		}
+		finally {
+			this.lock.readLock().unlock();
+		}
 	}
 
 	/**
 	 * Returns a String representation of the history event list.
 	 */
 	public String toString() {
-		return this.events.toString();
+		try {
+			this.lock.readLock().lock();
+			return this.events.toString();
+		}
+		finally {
+			this.lock.readLock().unlock();
+		}
 	}
-
 }

org.springframework.integration/src/test/java/org/springframework/integration/history/MessageHistoryTests.java

@@ -0,0 +1,72 @@
+/*
+ * Copyright 2002-2008 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.integration.history;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+
+import org.junit.Test;
+import org.springframework.integration.support.ComponentMetadata;
+
+/**
+ * @author Oleg Zhurakousky
+ * @since 2.0
+ */
+public class MessageHistoryTests {
+	private long times = 1000;
+	private ExecutorService executor = Executors.newCachedThreadPool();
+	@Test
+	public void testConcurrentModificationsOnObjectMethods() throws Exception{
+		final MessageHistory history = new MessageHistory();
+		
+		executor.execute(new Runnable() {
+			public void run() {
+				for (int i = 0; i < times; i++) {
+					ComponentMetadata event = new ComponentMetadata();
+					event.setAttribute("foo", "foo");
+					event.setAttribute("bar", "bar");
+					event.setComponentName("MessageHistoryTests");
+					history.addEvent(event);
+				}
+			}
+		});
+		
+		executor.execute(new Runnable() {
+			public void run() {
+				for (int i = 0; i < times; i++) {
+					history.toString();
+				}	
+			}
+		});
+		executor.execute(new Runnable() {
+			public void run() {
+				for (int i = 0; i < times; i++) {
+					history.hashCode();
+				}	
+			}
+		});
+		executor.execute(new Runnable() {
+			public void run() {
+				for (int i = 0; i < times; i++) {
+					history.equals(new Object());
+				}	
+			}
+		});
+		executor.shutdown();
+		executor.awaitTermination(3, TimeUnit.SECONDS);
+	}
+}