handled case where active session can be null and that is allowed

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

@@ -242,7 +242,8 @@ public class FlowExecutionImpl implements FlowExecution, Externalizable {
 	}
 
 	public void resume(ExternalContext externalContext) throws FlowExecutionException, IllegalStateException {
-		Assert.state(status == FlowExecutionStatus.STARTED, "This flow execution cannot be resumed; it is not active");
+		Assert.state(status == FlowExecutionStatus.STARTED,
+				"This flow execution cannot be resumed; it is not started or has ended");
 		if (logger.isDebugEnabled()) {
 			logger.debug("Resuming in " + externalContext);
 		}
@@ -376,6 +377,9 @@ public class FlowExecutionImpl implements FlowExecution, Externalizable {
 
 	void endActiveFlowSession(String outcome, MutableAttributeMap output, RequestControlContext context) {
 		FlowSessionImpl session = getActiveSessionInternal();
+		if (session == null) {
+			throw new IllegalArgumentException("Cannot end the active FlowSession when one has not been activated");
+		}
 		if (session.isRoot()) {
 			status = FlowExecutionStatus.ENDING;
 		}
@@ -548,18 +552,16 @@ public class FlowExecutionImpl implements FlowExecution, Externalizable {
 	 * @return the new flow session
 	 */
 	private FlowSessionImpl activateSession(Flow flow) {
-		FlowSessionImpl session;
-		if (!flowSessions.isEmpty()) {
-			FlowSessionImpl parent = getActiveSessionInternal();
-			session = createFlowSession(flow, parent);
-		} else {
-			session = createFlowSession(flow, null);
-		}
+		FlowSessionImpl parent = getActiveSessionInternal();
+		FlowSessionImpl session = createFlowSession(flow, parent);
 		flowSessions.add(session);
 		return session;
 	}
 
 	private FlowSessionImpl getActiveSessionInternal() {
+		if (flowSessions.isEmpty()) {
+			return null;
+		}
 		return (FlowSessionImpl) flowSessions.getLast();
 	}
 
@@ -645,8 +647,9 @@ public class FlowExecutionImpl implements FlowExecution, Externalizable {
 	 * Returns the current flow which may or may not yet be active.
 	 */
 	private Flow getCurrentFlow() {
-		if (isActive()) {
-			return getActiveSessionInternal().getFlow();
+		FlowSessionImpl session = getActiveSessionInternal();
+		if (session != null) {
+			return session.getFlow();
 		} else {
 			return flow;
 		}
@@ -654,8 +657,11 @@ public class FlowExecutionImpl implements FlowExecution, Externalizable {
 
 	private State getCurrentState() {
 		FlowSessionImpl session = getActiveSessionInternal();
-		State currentState = (State) session.getState();
-		return currentState;
+		if (session != null) {
+			return (State) session.getState();
+		} else {
+			return null;
+		}
 	}
 
 }

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

@@ -32,6 +32,7 @@ import org.springframework.webflow.execution.Event;
 import org.springframework.webflow.execution.FlowExecutionContext;
 import org.springframework.webflow.execution.FlowExecutionException;
 import org.springframework.webflow.execution.FlowExecutionKey;
+import org.springframework.webflow.execution.FlowSession;
 import org.springframework.webflow.execution.View;
 
 /**
@@ -98,11 +99,13 @@ class RequestControlContextImpl implements RequestControlContext {
 	// implementing RequestContext
 
 	public FlowDefinition getActiveFlow() {
-		return flowExecution.getActiveSession().getDefinition();
+		FlowSession session = flowExecution.getActiveSession();
+		return session != null ? session.getDefinition() : null;
 	}
 
 	public StateDefinition getCurrentState() {
-		return flowExecution.getActiveSession().getState();
+		FlowSession session = flowExecution.getActiveSession();
+		return session != null ? session.getState() : null;
 	}
 
 	public TransitionDefinition getMatchingTransition(String eventId) throws IllegalStateException {
@@ -122,11 +125,13 @@ class RequestControlContextImpl implements RequestControlContext {
 	}
 
 	public MutableAttributeMap getViewScope() throws IllegalStateException {
-		return flowExecution.getActiveSession().getViewScope();
+		FlowSession session = flowExecution.getActiveSession();
+		return session != null ? session.getViewScope() : null;
 	}
 
 	public MutableAttributeMap getFlowScope() {
-		return flowExecution.getActiveSession().getScope();
+		FlowSession session = flowExecution.getActiveSession();
+		return session != null ? session.getScope() : null;
 	}
 
 	public MutableAttributeMap getConversationScope() {

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

@@ -90,9 +90,9 @@ public interface FlowExecutionContext {
 	/**
 	 * Returns the active flow session of this flow execution. The active flow session is the currently executing
 	 * session. It may be the "root flow" session, or it may be a subflow session if this flow execution has spawned a
-	 * subflow. Returns null of this flow execution is in the process of starting or has ended.
+	 * subflow. Returns null of this flow execution is in the process of starting.
 	 * @return the active flow session
-	 * @throws IllegalStateException if this flow execution has not been started at all
+	 * @throws IllegalStateException if this flow execution has not been started at all or has ended
 	 */
 	public FlowSession getActiveSession() throws IllegalStateException;
 

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

@@ -106,17 +106,21 @@ public interface RequestContext {
 	/**
 	 * Returns a mutable map for accessing and/or setting attributes in view scope. <b>View scoped attributes exist for
 	 * the life of the current view state.</b>
-	 * @return the view scope
+	 * @return the view scope, or null if the flow execution is in the process of starting but has not yet completed
+	 * startup
 	 * @see #inViewState()
-	 * @throws IllegalStateException this flow is not in a view-state
+	 * @throws IllegalStateException if this flow is not in a view-state, or the flow execution has not been started at
+	 * all or has ended
 	 */
 	public MutableAttributeMap getViewScope() throws IllegalStateException;
 
 	/**
 	 * Returns a mutable map for accessing and/or setting attributes in flow scope. <b>Flow scoped attributes exist for
 	 * the life of the active flow session.</b>
-	 * @return the flow scope
+	 * @return the flow scope, or null if the the flow execution is in the process of starting but has not yet completed
+	 * startup
 	 * @see FlowSession
+	 * @throws IllegalStateException if the flow execution has not been started at all or has ended
 	 */
 	public MutableAttributeMap getFlowScope();
 

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

@@ -148,6 +148,8 @@ public class FlowExecutionImplTests extends TestCase {
 		} catch (FlowExecutionException e) {
 			assertEquals(flow.getId(), e.getFlowId());
 			assertNull(e.getStateId());
+			assertTrue(e.getCause() instanceof IllegalStateException);
+			assertTrue(e.getCause().getMessage().equals("Oops"));
 		}
 	}