Add global Validator bean to WebReactiveConfiguration

spring-web-reactive/build.gradle

@@ -111,6 +111,7 @@ dependencies {
 	optional "org.eclipse.jetty:jetty-servlet:${jettyVersion}"
 	optional("org.freemarker:freemarker:2.3.23")
 	optional("com.fasterxml:aalto-xml:1.0.0")
+	optional("javax.validation:validation-api:1.0.0.GA")
 
 	provided "javax.servlet:javax.servlet-api:3.1.0"
 

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

@@ -22,6 +22,8 @@ import java.util.Map;
 
 import reactor.core.converter.DependencyUtils;
 
+import org.springframework.beans.BeanUtils;
+import org.springframework.beans.factory.BeanInitializationException;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.ApplicationContextAware;
 import org.springframework.context.annotation.Bean;
@@ -48,6 +50,8 @@ import org.springframework.http.converter.reactive.CodecHttpMessageConverter;
 import org.springframework.http.converter.reactive.HttpMessageConverter;
 import org.springframework.http.converter.reactive.ResourceHttpMessageConverter;
 import org.springframework.util.ClassUtils;
+import org.springframework.validation.Errors;
+import org.springframework.validation.Validator;
 import org.springframework.web.reactive.accept.RequestedContentTypeResolver;
 import org.springframework.web.reactive.accept.RequestedContentTypeResolverBuilder;
 import org.springframework.web.reactive.result.SimpleHandlerAdapter;
@@ -185,6 +189,7 @@ public class WebReactiveConfiguration implements ApplicationContextAware {
 
 		adapter.setMessageConverters(getMessageConverters());
 		adapter.setConversionService(mvcConversionService());
+		adapter.setValidator(mvcValidator());
 
 		return adapter;
 	}
@@ -284,6 +289,46 @@ public class WebReactiveConfiguration implements ApplicationContextAware {
 		}
 	}
 
+	/**
+	 * Return a global {@link Validator} instance for example for validating
+	 * {@code @RequestBody} method arguments.
+	 * <p>Delegates to {@link #getValidator()} first. If that returns {@code null}
+	 * checks the classpath for the presence of a JSR-303 implementations
+	 * before creating a {@code OptionalValidatorFactoryBean}. If a JSR-303
+	 * implementation is not available, a "no-op" {@link Validator} is returned.
+	 */
+	@Bean
+	public Validator mvcValidator() {
+		Validator validator = getValidator();
+		if (validator == null) {
+			if (ClassUtils.isPresent("javax.validation.Validator", getClass().getClassLoader())) {
+				Class<?> clazz;
+				try {
+					String name = "org.springframework.validation.beanvalidation.OptionalValidatorFactoryBean";
+					clazz = ClassUtils.forName(name, classLoader);
+				}
+				catch (ClassNotFoundException ex) {
+					throw new BeanInitializationException("Could not find default validator class", ex);
+				}
+				catch (LinkageError ex) {
+					throw new BeanInitializationException("Could not load default validator class", ex);
+				}
+				validator = (Validator) BeanUtils.instantiate(clazz);
+			}
+			else {
+				validator = new NoOpValidator();
+			}
+		}
+		return validator;
+	}
+
+	/**
+	 * Override this method to provide a custom {@link Validator}.
+	 */
+	protected Validator getValidator() {
+		return null;
+	}
+
 	@Bean
 	public SimpleHandlerAdapter simpleHandlerAdapter() {
 		return new SimpleHandlerAdapter();
@@ -317,4 +362,17 @@ public class WebReactiveConfiguration implements ApplicationContextAware {
 	protected void configureViewResolvers(ViewResolverRegistry registry) {
 	}
 
+
+	private static final class NoOpValidator implements Validator {
+
+		@Override
+		public boolean supports(Class<?> clazz) {
+			return false;
+		}
+
+		@Override
+		public void validate(Object target, Errors errors) {
+		}
+	}
+
 }

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

@@ -39,7 +39,7 @@ import org.springframework.http.converter.reactive.CodecHttpMessageConverter;
 import org.springframework.http.converter.reactive.HttpMessageConverter;
 import org.springframework.ui.ExtendedModelMap;
 import org.springframework.ui.ModelMap;
-import org.springframework.util.ObjectUtils;
+import org.springframework.validation.Validator;
 import org.springframework.web.method.HandlerMethod;
 import org.springframework.web.method.annotation.ExceptionHandlerMethodResolver;
 import org.springframework.web.reactive.HandlerAdapter;
@@ -67,6 +67,8 @@ public class RequestMappingHandlerAdapter implements HandlerAdapter, BeanFactory
 
 	private ConversionService conversionService = new DefaultFormattingConversionService();
 
+	private Validator validator;
+
 	private ConfigurableBeanFactory beanFactory;
 
 	private final Map<Class<?>, ExceptionHandlerMethodResolver> exceptionHandlerCache = new ConcurrentHashMap<>(64);
@@ -141,6 +143,23 @@ public class RequestMappingHandlerAdapter implements HandlerAdapter, BeanFactory
 		return this.conversionService;
 	}
 
+	/**
+	 * Configure a Validator for validation of controller method arguments such
+	 * as {@code @RequestBody}.
+	 *
+	 * TODO: this may be replaced by DataBinder
+	 */
+	public void setValidator(Validator validator) {
+		this.validator = validator;
+	}
+
+	/**
+	 * Return the configured Validator.
+	 */
+	public Validator getValidator() {
+		return this.validator;
+	}
+
 	/**
 	 * A {@link ConfigurableBeanFactory} is expected for resolving expressions
 	 * in method argument default values.
@@ -173,7 +192,7 @@ public class RequestMappingHandlerAdapter implements HandlerAdapter, BeanFactory
 		resolvers.add(new RequestParamMapMethodArgumentResolver());
 		resolvers.add(new PathVariableMethodArgumentResolver(cs, getBeanFactory()));
 		resolvers.add(new PathVariableMapMethodArgumentResolver());
-		resolvers.add(new RequestBodyArgumentResolver(getMessageConverters(), cs));
+		resolvers.add(new RequestBodyArgumentResolver(getMessageConverters(), cs, getValidator()));
 		resolvers.add(new RequestHeaderMethodArgumentResolver(cs, getBeanFactory()));
 		resolvers.add(new RequestHeaderMapMethodArgumentResolver());
 		resolvers.add(new CookieValueMethodArgumentResolver(cs, getBeanFactory()));

spring-web-reactive/src/test/java/org/springframework/web/reactive/config/WebReactiveConfigurationTests.java

@@ -20,7 +20,6 @@ import java.nio.ByteBuffer;
 import java.util.Collections;
 import java.util.List;
 import java.util.concurrent.CompletableFuture;
-
 import javax.xml.bind.annotation.XmlRootElement;
 
 import org.junit.Before;
@@ -50,6 +49,8 @@ import org.springframework.http.server.reactive.MockServerHttpRequest;
 import org.springframework.http.server.reactive.MockServerHttpResponse;
 import org.springframework.util.MimeType;
 import org.springframework.util.MimeTypeUtils;
+import org.springframework.validation.Validator;
+import org.springframework.validation.beanvalidation.OptionalValidatorFactoryBean;
 import org.springframework.web.reactive.accept.RequestedContentTypeResolver;
 import org.springframework.web.reactive.result.method.annotation.RequestMappingHandlerAdapter;
 import org.springframework.web.reactive.result.method.annotation.RequestMappingHandlerMapping;
@@ -148,6 +149,11 @@ public class WebReactiveConfigurationTests {
 		name = "mvcConversionService";
 		ConversionService service = context.getBean(name, ConversionService.class);
 		assertSame(service, adapter.getConversionService());
+
+		name = "mvcValidator";
+		Validator validator = context.getBean(name, Validator.class);
+		assertSame(validator, adapter.getValidator());
+		assertEquals(OptionalValidatorFactoryBean.class, validator.getClass());
 	}
 
 	@Test