Prevent NPE in Mojarra when creating initial view

Refactor JsfViewFactory to only attempt a restoreView when state is
available. This prevents a NullPointerException from being thrown
when using Mojarra with partial state saving disabled. This change
also makes Web Flow behave in a similar way to the standard
FacesServlet.

Issue: SWF-1571

spring-faces/src/main/java/org/springframework/faces/webflow/FlowResponseStateManager.java

@@ -142,4 +142,13 @@ public class FlowResponseStateManager extends ResponseStateManagerWrapper {
 			writer.endElement("input");
 		}
 	}
+
+	/**
+	 * Determine if the request context has existing state.
+	 * @param context the request context
+	 * @return {@code true} if the context has state
+	 */
+	static boolean hasState(RequestContext context) {
+		return (context != null) && (context.getViewScope().contains(FACES_VIEW_STATE));
+	}
 }

spring-faces/src/main/java/org/springframework/faces/webflow/JsfViewFactory.java

@@ -132,7 +132,12 @@ public class JsfViewFactory implements ViewFactory {
 
 	private UIViewRoot getViewStateViewRoot(RequestContext context, FacesContext facesContext, ViewHandler viewHandler,
 			String viewName) {
-		UIViewRoot viewRoot = viewHandler.restoreView(facesContext, viewName);
+		UIViewRoot viewRoot = null;
+		if (FlowResponseStateManager.hasState(context)) {
+			// Only try an initial restore if we have state (see SWF-1571)
+			viewRoot = viewHandler.restoreView(facesContext, viewName);
+		}
+
 		if (viewRoot != null) {
 			if (logger.isDebugEnabled()) {
 				logger.debug("UIViewRoot restored for '" + viewName + "'");
@@ -144,6 +149,7 @@ public class JsfViewFactory implements ViewFactory {
 			}
 			viewRoot = viewHandler.createView(facesContext, viewName);
 		}
+
 		return viewRoot;
 	}
 

spring-faces/src/test/java/org/springframework/faces/webflow/JsfViewFactoryTests.java

@@ -72,12 +72,15 @@ public class JsfViewFactoryTests extends TestCase {
 
 	private final MockHttpServletResponse response = new MockHttpServletResponse();
 
+	private LocalAttributeMap<Object> viewScope = new LocalAttributeMap<Object>();
+
 	protected void setUp() throws Exception {
 		configureJsf();
 		this.extContext.setNativeContext(this.servletContext);
 		this.extContext.setNativeRequest(this.request);
 		this.extContext.setNativeResponse(this.response);
 		RequestContextHolder.setRequestContext(this.context);
+		EasyMock.expect(this.context.getViewScope()).andStubReturn(this.viewScope);
 		EasyMock.expect(this.context.getFlashScope()).andStubReturn(this.flashMap);
 		EasyMock.expect(this.context.getExternalContext()).andStubReturn(this.extContext);
 		EasyMock.expect(this.context.getRequestParameters()).andStubReturn(
@@ -148,6 +151,7 @@ public class JsfViewFactoryTests extends TestCase {
 		EasyMock.expectLastCall().andReturn(true);
 
 		EasyMock.replay(new Object[] { this.context });
+		setupViewState();
 
 		View restoredView = this.factory.getView(this.context);
 
@@ -194,6 +198,7 @@ public class JsfViewFactoryTests extends TestCase {
 		EasyMock.expectLastCall().andReturn(true);
 
 		EasyMock.replay(new Object[] { this.context });
+		setupViewState();
 
 		View restoredView = this.factory.getView(this.context);
 
@@ -229,6 +234,7 @@ public class JsfViewFactoryTests extends TestCase {
 		EasyMock.expectLastCall().andReturn(true);
 
 		EasyMock.replay(new Object[] { this.context });
+		setupViewState();
 
 		View restoredView = this.factory.getView(this.context);
 
@@ -279,6 +285,7 @@ public class JsfViewFactoryTests extends TestCase {
 
 		this.context.inViewState();
 		EasyMock.expectLastCall().andReturn(true);
+		setupViewState();
 
 		EasyMock.replay(new Object[] { this.context });
 		this.factory.getView(this.context);
@@ -289,6 +296,10 @@ public class JsfViewFactoryTests extends TestCase {
 				.getExceptionQueuedEventContext().getException());
 	}
 
+	private void setupViewState() {
+		this.viewScope.put(FlowResponseStateManager.FACES_VIEW_STATE, "X");
+	}
+
 	private class NoExecutionLifecycle extends FlowLifecycle {
 
 		public NoExecutionLifecycle(Lifecycle delegate) {