improved conversation locking

spring-webflow/src/main/java/org/springframework/webflow/conversation/impl/ContainedConversation.java

@@ -101,7 +101,6 @@ class ContainedConversation implements Conversation, Serializable {
 			logger.debug("Unlocking conversation " + id);
 		}
 		lock.unlock();
-
 		// re-bind the conversation container in the session
 		// this is required to make session replication work correctly in
 		// a clustered environment

spring-webflow/src/main/java/org/springframework/webflow/conversation/impl/JdkConcurrentConversationLock.java

@@ -16,6 +16,7 @@
 package org.springframework.webflow.conversation.impl;
 
 import java.io.Serializable;
+import java.util.concurrent.TimeUnit;
 import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReentrantLock;
 
@@ -32,8 +33,21 @@ class JdkConcurrentConversationLock implements ConversationLock, Serializable {
 	 */
 	private Lock lock = new ReentrantLock();
 
+	private int timeoutSeconds = 30;
+
+	public void setTimeoutSeconds(int timeoutSeconds) {
+		this.timeoutSeconds = timeoutSeconds;
+	}
+
 	public void lock() {
-		lock.lock();
+		try {
+			boolean acquired = lock.tryLock(timeoutSeconds, TimeUnit.SECONDS);
+			if (!acquired) {
+				throw new LockException("Unable to acquire conversation lock after " + timeoutSeconds + " seconds");
+			}
+		} catch (InterruptedException e) {
+			throw new IllegalStateException("Unable to acquire conversation lock - thread interrupted", e);
+		}
 	}
 
 	public void unlock() {

spring-webflow/src/main/java/org/springframework/webflow/conversation/impl/LockException.java

@@ -0,0 +1,9 @@
+package org.springframework.webflow.conversation.impl;
+
+import org.springframework.webflow.conversation.ConversationException;
+
+public class LockException extends ConversationException {
+	public LockException(String message) {
+		super(message);
+	}
+}

spring-webflow/src/main/java/org/springframework/webflow/conversation/impl/UtilConcurrentConversationLock.java

@@ -34,15 +34,24 @@ class UtilConcurrentConversationLock implements ConversationLock {
 	 */
 	private final ReentrantLock lock = new ReentrantLock();
 
+	private int timeoutMills;
+
+	public void setTimeoutSeconds(int timeoutSeconds) {
+		this.timeoutMills = timeoutSeconds * 1000;
+	}
+
 	/**
 	 * Acquires the lock.
 	 * @throws SystemInterruptedException if the lock cannot be acquired due to interruption
 	 */
 	public void lock() {
 		try {
-			lock.acquire();
+			boolean acquired = lock.attempt(timeoutMills);
+			if (!acquired) {
+				throw new LockException("Unable to acquire conversation lock after " + timeoutMills / 1000 + " seconds");
+			}
 		} catch (InterruptedException e) {
-			throw new SystemInterruptedException("Unable to acquire lock.", e);
+			throw new SystemInterruptedException("Unable to acquire conversation lock - thread interrupted", e);
 		}
 	}