Allow MVC handler methods to return any CharSequence type as view name

Issue: SPR-13165

Author: jhoeller

spring-test/src/test/java/org/springframework/test/web/servlet/samples/standalone/RedirectTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2015 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -39,16 +39,19 @@
  * Redirect scenarios including saving and retrieving flash attributes.
  *
  * @author Rossen Stoyanchev
+ * @author Juergen Hoeller
  */
 public class RedirectTests {
 
 	private MockMvc mockMvc;
 
+
 	@Before
 	public void setup() {
 		this.mockMvc = standaloneSetup(new PersonController()).build();
 	}
 
+
 	@Test
 	public void save() throws Exception {
 		this.mockMvc.perform(post("/persons").param("name", "Andy"))
@@ -60,6 +63,17 @@ public void save() throws Exception {
 			.andExpect(flash().attribute("message", "success!"));
 	}
 
+	@Test
+	public void saveSpecial() throws Exception {
+		this.mockMvc.perform(post("/people").param("name", "Andy"))
+				.andExpect(status().isFound())
+				.andExpect(redirectedUrl("/persons/Joe"))
+				.andExpect(model().size(1))
+				.andExpect(model().attributeExists("name"))
+				.andExpect(flash().attributeCount(1))
+				.andExpect(flash().attribute("message", "success!"));
+	}
+
 	@Test
 	public void saveWithErrors() throws Exception {
 		this.mockMvc.perform(post("/persons"))
@@ -70,6 +84,16 @@ public void saveWithErrors() throws Exception {
 			.andExpect(flash().attributeCount(0));
 	}
 
+	@Test
+	public void saveSpecialWithErrors() throws Exception {
+		this.mockMvc.perform(post("/people"))
+				.andExpect(status().isOk())
+				.andExpect(forwardedUrl("persons/add"))
+				.andExpect(model().size(1))
+				.andExpect(model().attributeExists("person"))
+				.andExpect(flash().attributeCount(0));
+	}
+
 	@Test
 	public void getPerson() throws Exception {
 		this.mockMvc.perform(get("/persons/Joe").flashAttr("message", "success!"))
@@ -100,5 +124,16 @@ public String save(@Valid Person person, Errors errors, RedirectAttributes redir
 			redirectAttrs.addFlashAttribute("message", "success!");
 			return "redirect:/persons/{name}";
 		}
+
+		@RequestMapping(value="/people", method=RequestMethod.POST)
+		public Object saveSpecial(@Valid Person person, Errors errors, RedirectAttributes redirectAttrs) {
+			if (errors.hasErrors()) {
+				return "persons/add";
+			}
+			redirectAttrs.addAttribute("name", "Joe");
+			redirectAttrs.addFlashAttribute("message", "success!");
+			return new StringBuilder("redirect:").append("/persons").append("/{name}");
+		}
 	}
+
 }

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/ViewNameMethodReturnValueHandler.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2015 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -24,8 +24,9 @@
 import org.springframework.web.servlet.RequestToViewNameTranslator;
 
 /**
- * Handles return values of types {@code void} and {@code String} interpreting
- * them as view name reference.
+ * Handles return values of types {@code void} and {@code String} interpreting them
+ * as view name reference. As of 4.2, it also handles general {@code CharSequence}
+ * types, e.g. {@code StringBuilder} or Groovy's {@code GString}, as view names.
  *
  * <p>A {@code null} return value, either due to a {@code void} return type or
  * as the actual return value is left as-is allowing the configured
@@ -37,6 +38,7 @@
  * the handlers that support these annotations.
  *
  * @author Rossen Stoyanchev
+ * @author Juergen Hoeller
  * @since 3.1
  */
 public class ViewNameMethodReturnValueHandler implements HandlerMethodReturnValueHandler {
@@ -68,24 +70,21 @@ public String[] getRedirectPatterns() {
 	@Override
 	public boolean supportsReturnType(MethodParameter returnType) {
 		Class<?> paramType = returnType.getParameterType();
-		return (void.class == paramType || String.class == paramType);
+		return (void.class == paramType || CharSequence.class.isAssignableFrom(paramType));
 	}
 
 	@Override
 	public void handleReturnValue(Object returnValue, MethodParameter returnType,
 			ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws Exception {
 
-		if (returnValue == null) {
-			return;
-		}
-		else if (returnValue instanceof String) {
-			String viewName = (String) returnValue;
+		if (returnValue instanceof CharSequence) {
+			String viewName = returnValue.toString();
 			mavContainer.setViewName(viewName);
 			if (isRedirectViewName(viewName)) {
 				mavContainer.setRedirectModelScenario(true);
 			}
 		}
-		else {
+		else if (returnValue != null){
 			// should not happen
 			throw new UnsupportedOperationException("Unexpected return type: " +
 					returnType.getParameterType().getName() + " in method: " + returnType.getMethod());
@@ -101,10 +100,7 @@ else if (returnValue instanceof String) {
 	 * reference; "false" otherwise.
 	 */
 	protected boolean isRedirectViewName(String viewName) {
-		if (PatternMatchUtils.simpleMatch(this.redirectPatterns, viewName)) {
-			return true;
-		}
-		return viewName.startsWith("redirect:");
+		return (PatternMatchUtils.simpleMatch(this.redirectPatterns, viewName) || viewName.startsWith("redirect:"));
 	}
 
 }