Remove SimpleResultHandler

There is really no need for a result handler dedicated to a void
return value and it's actually problematic to have it.

Each result handler treats void as necessary. For an @responsebody
method it means an empty body. For view resolution it means no specific
value was returned and we should procede with selecting a default view
name. Having a dedicated void result handler can interfere with this
especially since view resolution needs to be last in order.

At the same time there are cases when no result handling is needed
and the response is fully handled within the HandlerAdapter. This is
the case with WebHandler and the SimpleHandlerAdapter. For that case
we simply return mono.then(aVoid -> Mono.empty()) which effectively
returns an empty Mono and no result handling follows. The
HandlerAdapter already says you can return no values at all if the
response is fully handled.

Author: rstoyanchev

spring-web-reactive/src/main/java/org/springframework/web/reactive/config/WebReactiveConfiguration.java

@@ -55,7 +55,6 @@
 import org.springframework.web.reactive.accept.RequestedContentTypeResolver;
 import org.springframework.web.reactive.accept.RequestedContentTypeResolverBuilder;
 import org.springframework.web.reactive.result.SimpleHandlerAdapter;
-import org.springframework.web.reactive.result.SimpleResultHandler;
 import org.springframework.web.reactive.result.method.HandlerMethodArgumentResolver;
 import org.springframework.web.reactive.result.method.annotation.RequestMappingHandlerAdapter;
 import org.springframework.web.reactive.result.method.annotation.RequestMappingHandlerMapping;
@@ -321,11 +320,6 @@ public SimpleHandlerAdapter simpleHandlerAdapter() {
 		return new SimpleHandlerAdapter();
 	}
 
-	@Bean
-	public SimpleResultHandler simpleResultHandler() {
-		return new SimpleResultHandler();
-	}
-
 	@Bean
 	public ResponseEntityResultHandler responseEntityResultHandler() {
 		return new ResponseEntityResultHandler(getMessageWriters(), mvcContentTypeResolver());

spring-web-reactive/src/main/java/org/springframework/web/reactive/result/SimpleHandlerAdapter.java

@@ -60,7 +60,7 @@ public boolean supports(Object handler) {
 	public Mono<HandlerResult> handle(ServerWebExchange exchange, Object handler) {
 		WebHandler webHandler = (WebHandler) handler;
 		Mono<Void> mono = webHandler.handle(exchange);
-		return Mono.just(new HandlerResult(webHandler, mono, RETURN_TYPE));
+		return mono.then(aVoid -> Mono.empty());
 	}
 
 }

spring-web-reactive/src/main/java/org/springframework/web/reactive/result/SimpleResultHandler.java

@@ -143,11 +143,6 @@ public SimpleUrlHandlerMapping handlerMapping() {
 		public SimpleHandlerAdapter handlerAdapter() {
 			return new SimpleHandlerAdapter();
 		}
-
-		@Bean
-		public SimpleResultHandler resultHandler() {
-			return new SimpleResultHandler();
-		}
 	}
 
 }