OPEN - issue SWF-487: Add transitionExecuting flow execution listener hook.

http://jira.springframework.org/browse/SWF-487

spring-webflow/src/main/java/org/springframework/webflow/engine/impl/FlowExecutionImpl.java

@@ -350,6 +350,7 @@ public class FlowExecutionImpl implements FlowExecution, Externalizable {
 	}
 
 	void execute(Transition transition, RequestControlContext context) {
+		listeners.fireTransitionExecuting(context, transition);
 		transition.execute(getCurrentState(), context);
 	}
 

spring-webflow/src/main/java/org/springframework/webflow/engine/impl/FlowExecutionListeners.java

@@ -19,6 +19,7 @@ import org.springframework.webflow.core.collection.AttributeMap;
 import org.springframework.webflow.core.collection.MutableAttributeMap;
 import org.springframework.webflow.definition.FlowDefinition;
 import org.springframework.webflow.definition.StateDefinition;
+import org.springframework.webflow.definition.TransitionDefinition;
 import org.springframework.webflow.execution.Event;
 import org.springframework.webflow.execution.FlowExecutionException;
 import org.springframework.webflow.execution.FlowExecutionListener;
@@ -32,6 +33,7 @@ import org.springframework.webflow.execution.RequestContext;
  * 
  * @author Keith Donald
  * @author Erwin Vervaet
+ * @author Scott Andrews
  */
 class FlowExecutionListeners {
 
@@ -151,6 +153,15 @@ class FlowExecutionListeners {
 		}
 	}
 
+	/**
+	 * Notify all interested listeners that a transition is being entered in the flow execution.
+	 */
+	public void fireTransitionExecuting(RequestContext context, TransitionDefinition transition) {
+		for (int i = 0; i < listeners.length; i++) {
+			listeners[i].transitionExecuting(context, transition);
+		}
+	}
+
 	/**
 	 * Notify all interested listeners that a flow session was paused in the flow execution.
 	 */

spring-webflow/src/main/java/org/springframework/webflow/execution/FlowExecutionListener.java

@@ -19,6 +19,7 @@ import org.springframework.webflow.core.collection.AttributeMap;
 import org.springframework.webflow.core.collection.MutableAttributeMap;
 import org.springframework.webflow.definition.FlowDefinition;
 import org.springframework.webflow.definition.StateDefinition;
+import org.springframework.webflow.definition.TransitionDefinition;
 import org.springframework.webflow.engine.FlowExecutionExceptionHandler;
 
 /**
@@ -46,6 +47,7 @@ import org.springframework.webflow.engine.FlowExecutionExceptionHandler;
  * 
  * @author Keith Donald
  * @author Erwin Vervaet
+ * @author Scott Andrews
  */
 public interface FlowExecutionListener {
 
@@ -92,10 +94,17 @@ public interface FlowExecutionListener {
 	/**
 	 * Called when an event is signaled in the current state, but prior to any state transition.
 	 * @param context the source of the event
-	 * @param event the event that occured
+	 * @param event the event that occurred
 	 */
 	public void eventSignaled(RequestContext context, Event event);
 
+	/**
+	 * Called when a transition is matched but before the transition occurs.
+	 * @param context the source of the event
+	 * @param transition the proposed transition
+	 */
+	public void transitionExecuting(RequestContext context, TransitionDefinition transition);
+
 	/**
 	 * Called when a state transitions, after the transition is matched but before the transition occurs.
 	 * @param context the source of the event
@@ -105,7 +114,7 @@ public interface FlowExecutionListener {
 	public void stateEntering(RequestContext context, StateDefinition state) throws EnterStateVetoException;
 
 	/**
-	 * Called when a state transitions, after the transition occured.
+	 * Called when a state transitions, after the transition occurred.
 	 * @param context the source of the event
 	 * @param previousState <i>from</i> state of the transition
 	 * @param state <i>to</i> state of the transition

spring-webflow/src/main/java/org/springframework/webflow/execution/FlowExecutionListenerAdapter.java

@@ -19,6 +19,7 @@ import org.springframework.webflow.core.collection.AttributeMap;
 import org.springframework.webflow.core.collection.MutableAttributeMap;
 import org.springframework.webflow.definition.FlowDefinition;
 import org.springframework.webflow.definition.StateDefinition;
+import org.springframework.webflow.definition.TransitionDefinition;
 
 /**
  * An abstract adapter class for listeners (observers) of flow execution lifecycle events. The methods in this class are
@@ -26,6 +27,7 @@ import org.springframework.webflow.definition.StateDefinition;
  * 
  * @author Erwin Vervaet
  * @author Keith Donald
+ * @author Scott Andrews
  */
 public abstract class FlowExecutionListenerAdapter implements FlowExecutionListener {
 
@@ -47,6 +49,9 @@ public abstract class FlowExecutionListenerAdapter implements FlowExecutionListe
 	public void eventSignaled(RequestContext context, Event event) {
 	}
 
+	public void transitionExecuting(RequestContext context, TransitionDefinition transition) {
+	}
+
 	public void stateEntering(RequestContext context, StateDefinition state) throws EnterStateVetoException {
 	}
 

spring-webflow/src/test/java/org/springframework/webflow/engine/impl/FlowExecutionImplTests.java

@@ -25,7 +25,9 @@ import org.springframework.webflow.engine.Flow;
 import org.springframework.webflow.engine.RequestControlContext;
 import org.springframework.webflow.engine.State;
 import org.springframework.webflow.engine.StubViewFactory;
+import org.springframework.webflow.engine.Transition;
 import org.springframework.webflow.engine.ViewState;
+import org.springframework.webflow.engine.support.DefaultTargetStateResolver;
 import org.springframework.webflow.execution.FlowExecution;
 import org.springframework.webflow.execution.FlowExecutionException;
 import org.springframework.webflow.execution.FlowExecutionKey;
@@ -72,6 +74,7 @@ public class FlowExecutionImplTests extends TestCase {
 		assertEquals(1, mockListener.getSessionEndingCount());
 		assertEquals(1, mockListener.getSessionEndedCount());
 		assertEquals(0, mockListener.getEventSignaledCount());
+		assertEquals(0, mockListener.getTransitionExecutingCount());
 		assertEquals(0, mockListener.getPausedCount());
 		assertEquals(0, mockListener.getResumingCount());
 		assertEquals(0, mockListener.getExceptionThrownCount());
@@ -282,6 +285,29 @@ public class FlowExecutionImplTests extends TestCase {
 		}
 	}
 
+	public void testExecuteTransition() {
+		Flow flow = new Flow("flow");
+		ViewState state = new ViewState(flow, "view", new StubViewFactory()) {
+			public void resume(RequestControlContext context) {
+				context.execute(getRequiredTransition(context));
+			}
+		};
+		state.getTransitionSet().add(new Transition(new DefaultTargetStateResolver("finish")));
+		EndState end = new EndState(flow, "finish");
+		MockFlowExecutionListener mockListener = new MockFlowExecutionListener();
+		FlowExecutionListener[] listeners = new FlowExecutionListener[] { mockListener };
+		FlowExecutionImpl execution = new FlowExecutionImpl(flow);
+		execution.setListeners(listeners);
+		execution.setMessageContextFactory(new DefaultMessageContextFactory(new StaticMessageSource()));
+		execution.setKeyFactory(new MockFlowExecutionKeyFactory());
+		MockExternalContext context = new MockExternalContext();
+		execution.start(null, context);
+		assertEquals(0, mockListener.getTransitionExecutingCount());
+		execution.resume(context);
+		assertTrue(execution.hasEnded());
+		assertEquals(1, mockListener.getTransitionExecutingCount());
+	}
+
 	public void testRequestContextManagedOnStartAndResume() {
 		Flow flow = new Flow("flow");
 		new ViewState(flow, "view", new StubViewFactory()) {

spring-webflow/src/test/java/org/springframework/webflow/execution/MockFlowExecutionListener.java

@@ -20,12 +20,14 @@ import org.springframework.webflow.core.collection.AttributeMap;
 import org.springframework.webflow.core.collection.MutableAttributeMap;
 import org.springframework.webflow.definition.FlowDefinition;
 import org.springframework.webflow.definition.StateDefinition;
+import org.springframework.webflow.definition.TransitionDefinition;
 
 /**
  * Mock implementation of the <code>FlowExecutionListener</code> interface for use in unit tests.
  * 
  * @author Keith Donald
  * @author Erwin Vervaet
+ * @author Scott Andrews
  */
 public class MockFlowExecutionListener extends FlowExecutionListenerAdapter {
 
@@ -45,6 +47,8 @@ public class MockFlowExecutionListener extends FlowExecutionListenerAdapter {
 
 	private int stateEnteredCount;
 
+	private int transitionExecutingCount;
+
 	private int resumingCount;
 
 	private boolean paused;
@@ -157,6 +161,13 @@ public class MockFlowExecutionListener extends FlowExecutionListenerAdapter {
 		return stateEnteredCount;
 	}
 
+	/**
+	 * Returns the number of transitions entered so far.
+	 */
+	public int getTransitionExecutingCount() {
+		return transitionExecutingCount;
+	}
+
 	/**
 	 * Returns the number of events signaled so far.
 	 */
@@ -246,6 +257,10 @@ public class MockFlowExecutionListener extends FlowExecutionListenerAdapter {
 		stateEnteredCount++;
 	}
 
+	public void transitionExecuting(RequestContext context, TransitionDefinition transition) {
+		transitionExecutingCount++;
+	}
+
 	public void paused(RequestContext context) {
 		executing = false;
 		paused = true;
@@ -302,6 +317,7 @@ public class MockFlowExecutionListener extends FlowExecutionListenerAdapter {
 		sessionStartedCount = 0;
 		stateEnteringCount = 0;
 		stateEnteredCount = 0;
+		transitionExecutingCount = 0;
 		eventSignaledCount = 0;
 		pausedCount = 0;
 		resumingCount = 0;