SPR-6785 - Improve message error when the MarshallingView modelKey attribute is not valid

org.springframework.web.servlet/src/main/java/org/springframework/web/servlet/view/xml/MarshallingView.java

@@ -122,6 +122,9 @@ public class MarshallingView extends AbstractView {
 	protected Object locateToBeMarshalled(Map model) throws ServletException {
 		if (this.modelKey != null) {
 			Object o = model.get(this.modelKey);
+			if (o == null) {
+				throw new ServletException("Model contains no object with key [" + modelKey + "]");
+			}
 			if (!this.marshaller.supports(o.getClass())) {
 				throw new ServletException("Model object [" + o + "] retrieved via key [" + modelKey +
 						"] is not supported by the Marshaller");

org.springframework.web.servlet/src/test/java/org/springframework/web/servlet/view/xml/MarshallingViewTests.java

@@ -71,6 +71,29 @@ public class MarshallingViewTests {
 		verify(marshallerMock);
 	}
 
+	@Test
+	public void renderInvalidModelKey() throws Exception {
+		Object toBeMarshalled = new Object();
+		String modelKey = "key";
+		view.setModelKey("invalidKey");
+		Map model = new HashMap();
+		model.put(modelKey, toBeMarshalled);
+
+		MockHttpServletRequest request = new MockHttpServletRequest();
+		MockHttpServletResponse response = new MockHttpServletResponse();
+
+		replay(marshallerMock);
+		try {
+			view.render(model, request, response);
+			fail("ServletException expected");
+		}
+		catch (ServletException ex) {
+			// expected
+		}
+		assertEquals("Invalid content length", 0, response.getContentLength());
+		verify(marshallerMock);
+	}
+
 	@Test
 	public void renderModelKeyUnsupported() throws Exception {
 		Object toBeMarshalled = new Object();