Fix issue with "redirect:" when a media type is present

Issue: SPR-15291

spring-webflux/src/main/java/org/springframework/web/reactive/result/view/RedirectView.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -169,6 +169,11 @@ public class RedirectView extends AbstractUrlBasedView {
 	}
 
 
+	@Override
+	public boolean isRedirectView() {
+		return true;
+	}
+
 	@Override
 	public boolean checkResourceExists(Locale locale) throws Exception {
 		return true;

spring-webflux/src/main/java/org/springframework/web/reactive/result/view/View.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -47,6 +47,13 @@ public interface View {
 	 */
 	List<MediaType> getSupportedMediaTypes();
 
+	/**
+	 * Whether this View does rendering by performing a redirect.
+	 */
+	default boolean isRedirectView() {
+		return false;
+	}
+
 	/**
 	 * Render the view based on the given {@link HandlerResult}. Implementations
 	 * can access and use the model or only a specific attribute in it.

spring-webflux/src/main/java/org/springframework/web/reactive/result/view/ViewResolutionResultHandler.java

@@ -310,6 +310,12 @@ public class ViewResolutionResultHandler extends HandlerResultHandlerSupport
 	private Mono<? extends Void> render(List<View> views, Map<String, Object> model,
 			ServerWebExchange exchange) {
 
+		for (View view : views) {
+			if (view.isRedirectView()) {
+				return view.render(model, null, exchange);
+			}
+		}
+
 		List<MediaType> mediaTypes = getMediaTypes(views);
 		MediaType bestMediaType = selectMediaType(exchange, () -> mediaTypes);
 		if (bestMediaType != null) {

spring-webflux/src/test/java/org/springframework/web/reactive/result/view/ViewResolutionResultHandlerTests.java

@@ -33,6 +33,7 @@ import reactor.core.publisher.Mono;
 import reactor.test.StepVerifier;
 import rx.Completable;
 
+import org.springframework.context.support.StaticApplicationContext;
 import org.springframework.core.MethodParameter;
 import org.springframework.core.Ordered;
 import org.springframework.core.ResolvableType;
@@ -42,6 +43,7 @@ import org.springframework.core.io.buffer.support.DataBufferTestUtils;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.MediaType;
 import org.springframework.http.server.reactive.ServerHttpResponse;
+import org.springframework.mock.http.server.reactive.test.MockServerHttpResponse;
 import org.springframework.mock.http.server.reactive.test.MockServerWebExchange;
 import org.springframework.ui.ConcurrentModel;
 import org.springframework.ui.Model;
@@ -194,11 +196,10 @@ public class ViewResolutionResultHandlerTests {
 
 	@Test
 	public void handleWithMultipleResolvers() throws Exception {
-		Object returnValue = "profile";
-		MethodParameter returnType = on(Handler.class).annotNotPresent(ModelAttribute.class).resolveReturnType(String.class);
-		ViewResolver[] resolvers = {new TestViewResolver("account"), new TestViewResolver("profile")};
-
-		testHandle("/account", returnType, returnValue, "profile: {id=123}", resolvers);
+		testHandle("/account",
+				on(Handler.class).annotNotPresent(ModelAttribute.class).resolveReturnType(String.class),
+				"profile", "profile: {id=123}",
+				new TestViewResolver("account"), new TestViewResolver("profile"));
 	}
 
 	@Test
@@ -280,6 +281,25 @@ public class ViewResolutionResultHandlerTests {
 				.verify();
 	}
 
+	@Test // SPR-15291
+	public void contentNegotiationWithRedirect() throws Exception {
+
+		HandlerResult handlerResult = new HandlerResult(new Object(), "redirect:/",
+				on(Handler.class).annotNotPresent(ModelAttribute.class).resolveReturnType(String.class),
+				this.bindingContext);
+
+		UrlBasedViewResolver viewResolver = new UrlBasedViewResolver();
+		viewResolver.setApplicationContext(new StaticApplicationContext());
+		ViewResolutionResultHandler resultHandler = resultHandler(viewResolver);
+
+		MockServerWebExchange exchange = get("/account").accept(APPLICATION_JSON).toExchange();
+		resultHandler.handleResult(exchange, handlerResult).block(Duration.ZERO);
+
+		MockServerHttpResponse response = exchange.getResponse();
+		assertEquals(303, response.getStatusCode().value());
+		assertEquals("/", response.getHeaders().getLocation().toString());
+	}
+
 
 	private ViewResolutionResultHandler resultHandler(ViewResolver... resolvers) {
 		return resultHandler(Collections.emptyList(), resolvers);