polish

spring-webflow/src/main/java/org/springframework/webflow/engine/Transition.java

@@ -75,6 +75,16 @@ public class Transition extends AnnotatedObject implements TransitionDefinition
 	 */
 	private TargetStateResolver targetStateResolver;
 
+	/**
+	 * Create a new transition that always matches and always executes, but its execution does nothing by default.
+	 * @see #setMatchingCriteria(TransitionCriteria)
+	 * @see #setExecutionCriteria(TransitionCriteria)
+	 * @see #setTargetStateResolver(TargetStateResolver)
+	 */
+	public Transition() {
+		this(WildcardTransitionCriteria.INSTANCE, null);
+	}
+
 	/**
 	 * Create a new transition that always matches and always executes, transitioning to the target state calculated by
 	 * the provided targetStateResolver.

spring-webflow/src/main/java/org/springframework/webflow/engine/builder/support/TextToTargetStateResolver.java

@@ -71,6 +71,9 @@ class TextToTargetStateResolver extends AbstractConverter {
 
 	protected Object doConvert(Object source, Class targetClass, ConversionContext context) throws Exception {
 		String targetStateId = (String) source;
+		if (targetStateId == null) {
+			return null;
+		}
 		ExpressionParser parser = flowBuilderContext.getExpressionParser();
 		if (targetStateId.startsWith(BEAN_PREFIX)) {
 			return flowBuilderContext.getBeanFactory().getBean(targetStateId.substring(BEAN_PREFIX.length()));

spring-webflow/src/test/java/org/springframework/webflow/engine/TransitionTests.java

@@ -98,6 +98,25 @@ public class TransitionTests extends TestCase {
 		assertSame(source, context.getCurrentState());
 	}
 
+	public void testExecuteTransitionNullTargetStateResolver() {
+		Flow flow = new Flow("flow");
+		final TransitionableState source = new TransitionableState(flow, "state 1") {
+			public void exit(RequestControlContext context) {
+				exitCalled = true;
+			}
+
+			protected void doEnter(RequestControlContext context) throws FlowExecutionException {
+			}
+		};
+		MockRequestControlContext context = new MockRequestControlContext(flow);
+		context.setCurrentState(source);
+		Transition t = new Transition();
+		boolean stateExited = t.execute(source, context);
+		assertFalse(stateExited);
+		assertFalse(exitCalled);
+		assertSame(source, context.getCurrentState());
+	}
+
 	public void testTransitionExecutionRefused() {
 		Flow flow = new Flow("flow");
 		final TransitionableState source = new TransitionableState(flow, "state 1") {