Support Model as method argument and in HandlerResult

A model is created and passed to argument resolvers including a new
ModelArgumentResolver. The model is then exposed for result handling
as a field in HandlerResult.

spring-web-reactive/src/main/java/org/springframework/web/reactive/HandlerResult.java

@@ -22,6 +22,8 @@ import java.util.function.Function;
 import reactor.core.publisher.Mono;
 
 import org.springframework.core.ResolvableType;
+import org.springframework.ui.ExtendedModelMap;
+import org.springframework.ui.ModelMap;
 import org.springframework.util.Assert;
 
 /**
@@ -37,6 +39,8 @@ public class HandlerResult {
 
 	private final ResolvableType returnValueType;
 
+	private final ModelMap model;
+
 	private Function<Throwable, Mono<HandlerResult>> exceptionHandler;
 
 
@@ -45,13 +49,16 @@ public class HandlerResult {
 	 * @param handler the handler that handled the request
 	 * @param returnValue the return value from the handler possibly {@code null}
 	 * @param returnValueType the return value type
+	 * @param model the model used for request handling
 	 */
-	public HandlerResult(Object handler, Object returnValue, ResolvableType returnValueType) {
+	public HandlerResult(Object handler, Object returnValue, ResolvableType returnValueType, ModelMap model) {
 		Assert.notNull(handler, "'handler' is required");
 		Assert.notNull(returnValueType, "'returnValueType' is required");
+		Assert.notNull(model, "'model' is required");
 		this.handler = handler;
 		this.returnValue = Optional.ofNullable(returnValue);
 		this.returnValueType = returnValueType;
+		this.model = new ExtendedModelMap();
 	}
 
 
@@ -76,6 +83,14 @@ public class HandlerResult {
 		return this.returnValueType;
 	}
 
+	/**
+	 * Return the model used during request handling with attributes that may be
+	 * used to render HTML templates with.
+	 */
+	public ModelMap getModel() {
+		return this.model;
+	}
+
 	/**
 	 * Configure an exception handler that may be used to produce an alternative
 	 * result when result handling fails. Especially for an async return value

spring-web-reactive/src/main/java/org/springframework/web/reactive/handler/HttpHandlerHandlerAdapter.java

@@ -20,6 +20,8 @@ import org.reactivestreams.Publisher;
 import reactor.core.publisher.Mono;
 
 import org.springframework.core.ResolvableType;
+import org.springframework.ui.ExtendedModelMap;
+import org.springframework.ui.ModelMap;
 import org.springframework.web.reactive.DispatcherHandler;
 import org.springframework.web.reactive.HandlerAdapter;
 import org.springframework.web.reactive.HandlerResult;
@@ -48,7 +50,8 @@ public class HttpHandlerHandlerAdapter implements HandlerAdapter {
 	public Mono<HandlerResult> handle(ServerWebExchange exchange, Object handler) {
 		WebHandler webHandler = (WebHandler) handler;
 		Mono<Void> completion = webHandler.handle(exchange);
-		return Mono.just(new HandlerResult(webHandler, completion, PUBLISHER_VOID));
+		ModelMap model = new ExtendedModelMap();
+		return Mono.just(new HandlerResult(webHandler, completion, PUBLISHER_VOID, model));
 	}
 
 }

spring-web-reactive/src/main/java/org/springframework/web/reactive/method/HandlerMethodArgumentResolver.java

@@ -19,6 +19,7 @@ package org.springframework.web.reactive.method;
 import reactor.core.publisher.Mono;
 
 import org.springframework.core.MethodParameter;
+import org.springframework.ui.ModelMap;
 import org.springframework.web.server.ServerWebExchange;
 
 
@@ -34,7 +35,10 @@ public interface HandlerMethodArgumentResolver {
 	 * The returned {@link Mono} may produce one or zero values if the argument
 	 * does not resolve to any value, which will result in {@code null} passed
 	 * as the argument value.
+	 * @param parameter the method parameter
+	 * @param model the implicit model for request handling
+	 * @param exchange the current exchange
 	 */
-	Mono<Object> resolveArgument(MethodParameter parameter, ServerWebExchange exchange);
+	Mono<Object> resolveArgument(MethodParameter parameter, ModelMap model, ServerWebExchange exchange);
 
 }

spring-web-reactive/src/main/java/org/springframework/web/reactive/method/InvocableHandlerMethod.java

@@ -32,6 +32,7 @@ import org.springframework.core.GenericTypeResolver;
 import org.springframework.core.MethodParameter;
 import org.springframework.core.ParameterNameDiscoverer;
 import org.springframework.core.ResolvableType;
+import org.springframework.ui.ModelMap;
 import org.springframework.util.ObjectUtils;
 import org.springframework.util.ReflectionUtils;
 import org.springframework.web.method.HandlerMethod;
@@ -77,17 +78,20 @@ public class InvocableHandlerMethod extends HandlerMethod {
 	/**
 	 * Invoke the method and return a Publisher for the return value.
 	 * @param exchange the current exchange
+	 * @param model the model for request handling
 	 * @param providedArgs optional list of argument values to check by type
 	 * (via {@code instanceof}) for resolving method arguments.
 	 * @return Publisher that produces a single HandlerResult or an error signal;
 	 * never throws an exception
 	 */
-	public Mono<HandlerResult> invokeForRequest(ServerWebExchange exchange, Object... providedArgs) {
-		return resolveArguments(exchange, providedArgs).then(args -> {
+	public Mono<HandlerResult> invokeForRequest(ServerWebExchange exchange, ModelMap model,
+			Object... providedArgs) {
+
+		return resolveArguments(exchange, model, providedArgs).then(args -> {
 			try {
 				Object value = doInvoke(args);
 				ResolvableType type =  ResolvableType.forMethodParameter(getReturnType());
-				HandlerResult handlerResult = new HandlerResult(this, value, type);
+				HandlerResult handlerResult = new HandlerResult(this, value, type, model);
 				return Mono.just(handlerResult);
 			}
 			catch (InvocationTargetException ex) {
@@ -100,7 +104,7 @@ public class InvocableHandlerMethod extends HandlerMethod {
 		});
 	}
 
-	private Mono<Object[]> resolveArguments(ServerWebExchange exchange, Object... providedArgs) {
+	private Mono<Object[]> resolveArguments(ServerWebExchange exchange, ModelMap model, Object... providedArgs) {
 		if (ObjectUtils.isEmpty(getMethodParameters())) {
 			return NO_ARGS;
 		}
@@ -121,7 +125,7 @@ public class InvocableHandlerMethod extends HandlerMethod {
 								.findFirst()
 								.orElseThrow(() -> getArgError("No resolver for ", param, null));
 						try {
-							return resolver.resolveArgument(param, exchange)
+							return resolver.resolveArgument(param, model, exchange)
 									.defaultIfEmpty(NO_VALUE)
 									.otherwise(ex -> Mono.error(getArgError("Error resolving ", param, ex)))
 									.log("reactor.unresolved");

spring-web-reactive/src/main/java/org/springframework/web/reactive/method/annotation/ModelArgumentResolver.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2002-2016 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.web.reactive.method.annotation;
+
+import reactor.core.publisher.Mono;
+
+import org.springframework.core.MethodParameter;
+import org.springframework.ui.Model;
+import org.springframework.ui.ModelMap;
+import org.springframework.web.reactive.method.HandlerMethodArgumentResolver;
+import org.springframework.web.server.ServerWebExchange;
+
+/**
+ * Resolver for the {@link Model} controller method argument.
+ *
+ * @author Rossen Stoyanchev
+ */
+public class ModelArgumentResolver implements HandlerMethodArgumentResolver {
+
+
+	@Override
+	public boolean supportsParameter(MethodParameter parameter) {
+		return Model.class.isAssignableFrom(parameter.getParameterType());
+	}
+
+	@Override
+	public Mono<Object> resolveArgument(MethodParameter parameter, ModelMap model, ServerWebExchange exchange) {
+		return Mono.just(model);
+	}
+
+}

spring-web-reactive/src/main/java/org/springframework/web/reactive/method/annotation/RequestBodyArgumentResolver.java

@@ -28,6 +28,7 @@ import org.springframework.core.codec.Decoder;
 import org.springframework.core.convert.ConversionService;
 import org.springframework.core.io.buffer.DataBuffer;
 import org.springframework.http.MediaType;
+import org.springframework.ui.ModelMap;
 import org.springframework.util.Assert;
 import org.springframework.web.bind.annotation.RequestBody;
 import org.springframework.web.reactive.method.HandlerMethodArgumentResolver;
@@ -58,7 +59,9 @@ public class RequestBodyArgumentResolver implements HandlerMethodArgumentResolve
 	}
 
 	@Override
-	public Mono<Object> resolveArgument(MethodParameter parameter, ServerWebExchange exchange) {
+	public Mono<Object> resolveArgument(MethodParameter parameter, ModelMap model,
+			ServerWebExchange exchange) {
+
 		MediaType mediaType = exchange.getRequest().getHeaders().getContentType();
 		if (mediaType == null) {
 			mediaType = MediaType.APPLICATION_OCTET_STREAM;

spring-web-reactive/src/main/java/org/springframework/web/reactive/method/annotation/RequestMappingHandlerAdapter.java

@@ -38,6 +38,8 @@ import org.springframework.core.convert.ConversionService;
 import org.springframework.core.convert.support.DefaultConversionService;
 import org.springframework.core.io.buffer.DataBufferAllocator;
 import org.springframework.core.io.buffer.NettyDataBufferAllocator;
+import org.springframework.ui.ExtendedModelMap;
+import org.springframework.ui.ModelMap;
 import org.springframework.util.ObjectUtils;
 import org.springframework.web.method.HandlerMethod;
 import org.springframework.web.method.annotation.ExceptionHandlerMethodResolver;
@@ -64,7 +66,7 @@ public class RequestMappingHandlerAdapter implements HandlerAdapter, Initializin
 			new NettyDataBufferAllocator(new UnpooledByteBufAllocator(false));
 
 	private final Map<Class<?>, ExceptionHandlerMethodResolver> exceptionHandlerCache =
-			new ConcurrentHashMap<Class<?>, ExceptionHandlerMethodResolver>(64);
+			new ConcurrentHashMap<>(64);
 
 
 	/**
@@ -105,6 +107,7 @@ public class RequestMappingHandlerAdapter implements HandlerAdapter, Initializin
 
 			this.argumentResolvers.add(new RequestParamArgumentResolver());
 			this.argumentResolvers.add(new RequestBodyArgumentResolver(decoders, this.conversionService));
+			this.argumentResolvers.add(new ModelArgumentResolver());
 		}
 	}
 
@@ -118,8 +121,8 @@ public class RequestMappingHandlerAdapter implements HandlerAdapter, Initializin
 		HandlerMethod handlerMethod = (HandlerMethod) handler;
 		InvocableHandlerMethod invocable = new InvocableHandlerMethod(handlerMethod);
 		invocable.setHandlerMethodArgumentResolvers(this.argumentResolvers);
-
-		return invocable.invokeForRequest(exchange)
+		ModelMap model = new ExtendedModelMap();
+		return invocable.invokeForRequest(exchange, model)
 				.map(result -> result.setExceptionHandler(ex -> handleException(ex, handlerMethod, exchange)))
 				.otherwise(ex -> handleException(ex, handlerMethod, exchange));
 	}
@@ -135,7 +138,8 @@ public class RequestMappingHandlerAdapter implements HandlerAdapter, Initializin
 						logger.debug("Invoking @ExceptionHandler method: " + invocable);
 					}
 					invocable.setHandlerMethodArgumentResolvers(getArgumentResolvers());
-					return invocable.invokeForRequest(exchange, ex);
+					ExtendedModelMap errorModel = new ExtendedModelMap();
+					return invocable.invokeForRequest(exchange, errorModel, ex);
 				}
 				catch (Exception invocationEx) {
 					if (logger.isErrorEnabled()) {

spring-web-reactive/src/main/java/org/springframework/web/reactive/method/annotation/RequestParamArgumentResolver.java

@@ -19,6 +19,7 @@ package org.springframework.web.reactive.method.annotation;
 import reactor.core.publisher.Mono;
 
 import org.springframework.core.MethodParameter;
+import org.springframework.ui.ModelMap;
 import org.springframework.web.bind.annotation.RequestParam;
 import org.springframework.web.reactive.method.HandlerMethodArgumentResolver;
 import org.springframework.web.server.ServerWebExchange;
@@ -41,7 +42,7 @@ public class RequestParamArgumentResolver implements HandlerMethodArgumentResolv
 
 
 	@Override
-	public Mono<Object> resolveArgument(MethodParameter param, ServerWebExchange exchange) {
+	public Mono<Object> resolveArgument(MethodParameter param, ModelMap model, ServerWebExchange exchange) {
 		RequestParam annotation = param.getParameterAnnotation(RequestParam.class);
 		String name = (annotation.value().length() != 0 ? annotation.value() : param.getParameterName());
 		UriComponents uriComponents = UriComponentsBuilder.fromUri(exchange.getRequest().getURI()).build();