Add updateModel to BindingContext

The method includes logic that is currently in
ViewResolutionResultHandler but fits well in BindingContext and also
includes the call to saveModel method from the InitBinderBindingContext
subclass, which was called too early until now from
RequestMappingHandlerAdapter before the model has been fully updated.

This mirrors a similar method in ModelFactory on the Spring MVC side
which also combines those two tasks.

Closes gh-30821

Author: rstoyanchev

spring-webflux/src/main/java/org/springframework/web/reactive/BindingContext.java

@@ -17,16 +17,19 @@
 package org.springframework.web.reactive;
 
 import java.lang.annotation.Annotation;
+import java.util.Collection;
 import java.util.Collections;
 import java.util.Map;
 
 import reactor.core.publisher.Mono;
 
+import org.springframework.beans.BeanUtils;
 import org.springframework.core.MethodParameter;
 import org.springframework.core.ReactiveAdapterRegistry;
 import org.springframework.core.ResolvableType;
 import org.springframework.lang.Nullable;
 import org.springframework.ui.Model;
+import org.springframework.validation.BindingResult;
 import org.springframework.validation.DataBinder;
 import org.springframework.validation.support.BindingAwareConcurrentModel;
 import org.springframework.web.bind.support.WebBindingInitializer;
@@ -57,20 +60,30 @@ public class BindingContext {
 
 	private boolean methodValidationApplicable;
 
+	private final ReactiveAdapterRegistry reactiveAdapterRegistry;
+
 
 	/**
-	 * Create a new {@code BindingContext}.
+	 * Create an instance without an initializer.
 	 */
 	public BindingContext() {
 		this(null);
 	}
 
 	/**
-	 * Create a new {@code BindingContext} with the given initializer.
-	 * @param initializer the binding initializer to apply (may be {@code null})
+	 * Create an instance with the given initializer, which may be {@code null}.
 	 */
 	public BindingContext(@Nullable WebBindingInitializer initializer) {
+		this(initializer, ReactiveAdapterRegistry.getSharedInstance());
+	}
+
+	/**
+	 * Create an instance with the given initializer and {@code ReactiveAdapterRegistry}.
+	 * @since 6.1
+	 */
+	public BindingContext(@Nullable WebBindingInitializer initializer, ReactiveAdapterRegistry registry) {
 		this.initializer = initializer;
+		this.reactiveAdapterRegistry = new ReactiveAdapterRegistry();
 	}
 
 
@@ -151,6 +164,34 @@ protected WebExchangeDataBinder initDataBinder(WebExchangeDataBinder binder, Ser
 		return binder;
 	}
 
+	/**
+	 * Invoked before rendering to add {@link BindingResult} attributes where
+	 * necessary, and also to promote model attributes listed as
+	 * {@code @SessionAttributes} to the session.
+	 * @param exchange the current exchange
+	 * @since 6.1
+	 */
+	public void updateModel(ServerWebExchange exchange) {
+		Map<String, Object> model = getModel().asMap();
+		for (Map.Entry<String, Object> entry : model.entrySet()) {
+			String name = entry.getKey();
+			Object value = entry.getValue();
+			if (isBindingCandidate(name, value)) {
+				if (!model.containsKey(BindingResult.MODEL_KEY_PREFIX + name)) {
+					WebExchangeDataBinder binder = createDataBinder(exchange, value, name);
+					model.put(BindingResult.MODEL_KEY_PREFIX + name, binder.getBindingResult());
+				}
+			}
+		}
+	}
+
+	private boolean isBindingCandidate(String name, @Nullable Object value) {
+		return (!name.startsWith(BindingResult.MODEL_KEY_PREFIX) && value != null &&
+				!value.getClass().isArray() && !(value instanceof Collection) && !(value instanceof Map) &&
+				this.reactiveAdapterRegistry.getAdapter(null, value) == null &&
+				!BeanUtils.isSimpleValueType(value.getClass()));
+	}
+
 
 	/**
 	 * Extended variant of {@link WebExchangeDataBinder}, adding path variables.

spring-webflux/src/main/java/org/springframework/web/reactive/result/method/annotation/InitBinderBindingContext.java

@@ -18,6 +18,7 @@
 
 import java.util.List;
 
+import org.springframework.core.ReactiveAdapterRegistry;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
@@ -52,11 +53,11 @@ class InitBinderBindingContext extends BindingContext {
 
 	InitBinderBindingContext(
 			@Nullable WebBindingInitializer initializer, List<SyncInvocableHandlerMethod> binderMethods,
-			boolean methodValidationApplicable) {
+			boolean methodValidationApplicable, ReactiveAdapterRegistry registry) {
 
-		super(initializer);
+		super(initializer, registry);
 		this.binderMethods = binderMethods;
-		this.binderMethodContext = new BindingContext(initializer);
+		this.binderMethodContext = new BindingContext(initializer, registry);
 		setMethodValidationApplicable(methodValidationApplicable);
 	}
 
@@ -101,8 +102,8 @@ private void invokeBinderMethod(
 	}
 
 	/**
-	 * Provide the context required to apply {@link #saveModel()} after the
-	 * controller method has been invoked.
+	 * Provide the context required to promote model attributes listed as
+	 * {@code @SessionAttributes} to the session during {@link #updateModel}.
 	 */
 	public void setSessionContext(SessionAttributesHandler attributesHandler, WebSession session) {
 		this.saveModelOperation = () -> {
@@ -115,14 +116,12 @@ public void setSessionContext(SessionAttributesHandler attributesHandler, WebSes
 		};
 	}
 
-	/**
-	 * Save model attributes in the session based on a type-level declarations
-	 * in an {@code @SessionAttributes} annotation.
-	 */
-	public void saveModel() {
+	@Override
+	public void updateModel(ServerWebExchange exchange) {
 		if (this.saveModelOperation != null) {
 			this.saveModelOperation.run();
 		}
+		super.updateModel(exchange);
 	}
 
 }

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

@@ -186,12 +186,16 @@ public boolean supports(Object handler) {
 
 	@Override
 	public Mono<HandlerResult> handle(ServerWebExchange exchange, Object handler) {
+
+		Assert.state(this.methodResolver != null &&
+				this.modelInitializer != null && this.reactiveAdapterRegistry != null, "Not initialized");
+
 		HandlerMethod handlerMethod = (HandlerMethod) handler;
-		Assert.state(this.methodResolver != null && this.modelInitializer != null, "Not initialized");
 
 		InitBinderBindingContext bindingContext = new InitBinderBindingContext(
 				this.webBindingInitializer, this.methodResolver.getInitBinderMethods(handlerMethod),
-				this.methodResolver.hasMethodValidator() && handlerMethod.shouldValidateArguments());
+				this.methodResolver.hasMethodValidator() && handlerMethod.shouldValidateArguments(),
+				this.reactiveAdapterRegistry);
 
 		InvocableHandlerMethod invocableMethod = this.methodResolver.getRequestMappingMethod(handlerMethod);
 
@@ -202,7 +206,6 @@ public Mono<HandlerResult> handle(ServerWebExchange exchange, Object handler) {
 				.initModel(handlerMethod, bindingContext, exchange)
 				.then(Mono.defer(() -> invocableMethod.invoke(exchange, bindingContext)))
 				.doOnNext(result -> result.setExceptionHandler(exceptionHandler))
-				.doOnNext(result -> bindingContext.saveModel())
 				.onErrorResume(ex -> exceptionHandler.handleError(exchange, ex));
 	}
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -17,7 +17,6 @@
 package org.springframework.web.reactive.result.view;
 
 import java.util.ArrayList;
-import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
 import java.util.Locale;
@@ -41,9 +40,7 @@
 import org.springframework.lang.Nullable;
 import org.springframework.ui.Model;
 import org.springframework.util.StringUtils;
-import org.springframework.validation.BindingResult;
 import org.springframework.web.bind.annotation.ModelAttribute;
-import org.springframework.web.bind.support.WebExchangeDataBinder;
 import org.springframework.web.reactive.BindingContext;
 import org.springframework.web.reactive.HandlerResult;
 import org.springframework.web.reactive.HandlerResultHandler;
@@ -243,7 +240,7 @@ else if (View.class.isAssignableFrom(clazz)) {
 						viewsMono = resolveViews(getDefaultViewName(exchange), locale);
 					}
 					BindingContext bindingContext = result.getBindingContext();
-					updateBindingResult(bindingContext, exchange);
+					bindingContext.updateModel(exchange);
 					return viewsMono.flatMap(views -> render(views, model.asMap(), bindingContext, exchange));
 				});
 	}
@@ -289,27 +286,6 @@ private String getNameForReturnValue(MethodParameter returnType) {
 				.orElseGet(() -> Conventions.getVariableNameForParameter(returnType));
 	}
 
-	private void updateBindingResult(BindingContext context, ServerWebExchange exchange) {
-		Map<String, Object> model = context.getModel().asMap();
-		for (Map.Entry<String, Object> entry : model.entrySet()) {
-			String name = entry.getKey();
-			Object value = entry.getValue();
-			if (isBindingCandidate(name, value)) {
-				if (!model.containsKey(BindingResult.MODEL_KEY_PREFIX + name)) {
-					WebExchangeDataBinder binder = context.createDataBinder(exchange, value, name);
-					model.put(BindingResult.MODEL_KEY_PREFIX + name, binder.getBindingResult());
-				}
-			}
-		}
-	}
-
-	private boolean isBindingCandidate(String name, @Nullable Object value) {
-		return (!name.startsWith(BindingResult.MODEL_KEY_PREFIX) && value != null &&
-				!value.getClass().isArray() && !(value instanceof Collection) && !(value instanceof Map) &&
-				getAdapterRegistry().getAdapter(null, value) == null &&
-				!BeanUtils.isSimpleValueType(value.getClass()));
-	}
-
 	private Mono<? extends Void> render(List<View> views, Map<String, Object> model,
 			BindingContext bindingContext, ServerWebExchange exchange) {
 

spring-webflux/src/test/java/org/springframework/web/reactive/result/method/annotation/InitBinderBindingContextTests.java

@@ -133,7 +133,8 @@ private BindingContext createBindingContext(String methodName, Class<?>... param
 		handlerMethod.setParameterNameDiscoverer(new DefaultParameterNameDiscoverer());
 
 		return new InitBinderBindingContext(
-				this.bindingInitializer, Collections.singletonList(handlerMethod), false);
+				this.bindingInitializer, Collections.singletonList(handlerMethod), false,
+				ReactiveAdapterRegistry.getSharedInstance());
 	}
 
 

spring-webflux/src/test/java/org/springframework/web/reactive/result/method/annotation/ModelInitializerTests.java

@@ -144,7 +144,7 @@ public void saveModelAttributeToSession() {
 		assertThat(session).isNotNull();
 		assertThat(session.getAttributes()).isEmpty();
 
-		context.saveModel();
+		context.updateModel(this.exchange);
 		assertThat(session.getAttributes()).hasSize(1);
 		assertThat(((TestBean) session.getRequiredAttribute("bean")).getName()).isEqualTo("Bean");
 	}
@@ -164,7 +164,7 @@ public void retrieveModelAttributeFromSession() {
 		HandlerMethod handlerMethod = new HandlerMethod(controller, method);
 		this.modelInitializer.initModel(handlerMethod, context, this.exchange).block(TIMEOUT);
 
-		context.saveModel();
+		context.updateModel(this.exchange);
 		assertThat(session.getAttributes()).hasSize(1);
 		assertThat(((TestBean) session.getRequiredAttribute("bean")).getName()).isEqualTo("Session Bean");
 	}
@@ -197,7 +197,7 @@ public void clearModelAttributeFromSession() {
 		this.modelInitializer.initModel(handlerMethod, context, this.exchange).block(TIMEOUT);
 
 		context.getSessionStatus().setComplete();
-		context.saveModel();
+		context.updateModel(this.exchange);
 
 		assertThat(session.getAttributes()).isEmpty();
 	}
@@ -211,7 +211,8 @@ private InitBinderBindingContext getBindingContext(Object controller) {
 						.toList();
 
 		WebBindingInitializer bindingInitializer = new ConfigurableWebBindingInitializer();
-		return new InitBinderBindingContext(bindingInitializer, binderMethods, false);
+		return new InitBinderBindingContext(
+				bindingInitializer, binderMethods, false, ReactiveAdapterRegistry.getSharedInstance());
 	}