Refine validator and MVC validator configuration

Update `ValidationAutoConfiguration` and `WebMvcAutoConfiguration` to
ensure as much as possible that only a single Validator bean of each
type is registered.

Validation auto-configuration now does the following:
- If no validator is found: Registers a `LocalValidatorFactoryBean`
  (providing both Spring and JSR validation)
- If the user defines a Spring & JSR validator: Backs off
- If the user defines only a JSR validator: Adapts it to a Spring
  validator (without exposing another JSR implementation)

WebMvcAutoConfiguration auto-configuration has been updated to make
MVC validation follow common Spring Boot patterns:
- If not validator beans are found (due to the user excluding
  ValidationAutoConfiguration) a new `mvcValidator` bean will be
  registered.
- If a single validator bean is found it will be used for MVC
  validation.
- If multiple validator beans are defined it will either use the one
  named `mvcValidator` or it will register a new `mvcValidator` bean

Any automatically registered `mvcValidator` bean will not implement
the JSR validator interface.

Finally, it is no longer possible to provide an MVC validator via a
`WebMvcConfigurer`.

Fixes gh-8495

spring-boot-actuator/src/test/java/org/springframework/boot/actuate/autoconfigure/EndpointMvcIntegrationTests.java

@@ -41,6 +41,7 @@ import org.springframework.boot.actuate.endpoint.mvc.EndpointHandlerMappingCusto
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.autoconfigure.context.PropertyPlaceholderAutoConfiguration;
 import org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration;
+import org.springframework.boot.autoconfigure.validation.ValidationAutoConfiguration;
 import org.springframework.boot.autoconfigure.web.DispatcherServletAutoConfiguration;
 import org.springframework.boot.autoconfigure.web.EmbeddedServletContainerAutoConfiguration;
 import org.springframework.boot.autoconfigure.web.ErrorMvcAutoConfiguration;
@@ -156,9 +157,9 @@ public class EndpointMvcIntegrationTests {
 	@Documented
 	@Import({ EmbeddedServletContainerAutoConfiguration.class,
 			ServerPropertiesAutoConfiguration.class,
-			DispatcherServletAutoConfiguration.class, WebMvcAutoConfiguration.class,
+			DispatcherServletAutoConfiguration.class, ValidationAutoConfiguration.class,
-			JacksonAutoConfiguration.class, ErrorMvcAutoConfiguration.class,
+			WebMvcAutoConfiguration.class, JacksonAutoConfiguration.class,
-			PropertyPlaceholderAutoConfiguration.class })
+			ErrorMvcAutoConfiguration.class, PropertyPlaceholderAutoConfiguration.class })
 	protected @interface MinimalWebConfiguration {
 
 	}

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/validation/DefaultValidatorConfiguration.java

@@ -0,0 +1,47 @@
+/*
+ * Copyright 2012-2017 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.
+ * 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.boot.autoconfigure.validation;
+
+import org.springframework.beans.factory.config.BeanDefinition;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
+import org.springframework.boot.validation.MessageInterpolatorFactory;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Role;
+import org.springframework.validation.beanvalidation.LocalValidatorFactoryBean;
+
+/**
+ * Default validator configuration imported by {@link ValidationAutoConfiguration}.
+ *
+ * @author Stephane Nicoll
+ * @author Phillip Webb
+ */
+@Configuration
+class DefaultValidatorConfiguration {
+
+	@Bean
+	@ConditionalOnMissingBean(type = { "javax.validation.Validator",
+			"org.springframework.validation.Validator" })
+	@Role(BeanDefinition.ROLE_INFRASTRUCTURE)
+	public static LocalValidatorFactoryBean defaultValidator() {
+		LocalValidatorFactoryBean factoryBean = new LocalValidatorFactoryBean();
+		MessageInterpolatorFactory interpolatorFactory = new MessageInterpolatorFactory();
+		factoryBean.setMessageInterpolator(interpolatorFactory.getObject());
+		return factoryBean;
+	}
+
+}

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/validation/DelegatingValidator.java

@@ -0,0 +1,78 @@
+/*
+ * Copyright 2012-2017 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.
+ * 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.boot.autoconfigure.validation;
+
+import org.springframework.util.Assert;
+import org.springframework.validation.Errors;
+import org.springframework.validation.SmartValidator;
+import org.springframework.validation.Validator;
+import org.springframework.validation.beanvalidation.SpringValidatorAdapter;
+
+/**
+ * {@link Validator} implementation that delegates calls to another {@link Validator}.
+ * This {@link Validator} implements Spring's {@link SmartValidator} interface but does
+ * not implement the JSR-303 {@code javax.validator.Validator} interface.
+ *
+ * @author Phillip Webb
+ * @since 1.5.3
+ */
+public class DelegatingValidator implements SmartValidator {
+
+	private final Validator delegate;
+
+	/**
+	 * Create a new {@link DelegatingValidator} instance.
+	 * @param targetValidator the target JSR validator
+	 */
+	public DelegatingValidator(javax.validation.Validator targetValidator) {
+		this.delegate = new SpringValidatorAdapter(targetValidator);
+	}
+
+	/**
+	 * Create a new {@link DelegatingValidator} instance.
+	 * @param targetValidator the target validator
+	 */
+	public DelegatingValidator(Validator targetValidator) {
+		Assert.notNull(targetValidator, "Target Validator must not be null");
+		this.delegate = targetValidator;
+	}
+
+	@Override
+	public boolean supports(Class<?> clazz) {
+		return this.delegate.supports(clazz);
+	}
+
+	@Override
+	public void validate(Object target, Errors errors) {
+		this.delegate.validate(target, errors);
+	}
+
+	@Override
+	public void validate(Object target, Errors errors, Object... validationHints) {
+		if (this.delegate instanceof SmartValidator) {
+			((SmartValidator) this.delegate).validate(target, errors, validationHints);
+		}
+		else {
+			this.delegate.validate(target, errors);
+		}
+	}
+
+	protected final Validator getDelegate() {
+		return this.delegate;
+	}
+
+}

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/validation/Jsr303ValidatorAdapterConfiguration.java

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2012-2017 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.
+ * 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.boot.autoconfigure.validation;
+
+import javax.validation.Validator;
+
+import org.springframework.beans.factory.config.BeanDefinition;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnSingleCandidate;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Role;
+import org.springframework.validation.SmartValidator;
+
+/**
+ * JSR 303 adapter configration imported by {@link ValidationAutoConfiguration}.
+ *
+ * @author Stephane Nicoll
+ * @author Phillip Webb
+ */
+@Configuration
+class Jsr303ValidatorAdapterConfiguration {
+
+	@Bean
+	@ConditionalOnSingleCandidate(Validator.class)
+	@ConditionalOnMissingBean(org.springframework.validation.Validator.class)
+	@Role(BeanDefinition.ROLE_INFRASTRUCTURE)
+	public SmartValidator jsr303ValidatorAdapter(Validator validator) {
+		return new DelegatingValidator(validator);
+	}
+
+}

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/validation/ValidationAutoConfiguration.java

@@ -19,18 +19,16 @@ package org.springframework.boot.autoconfigure.validation;
 import javax.validation.Validator;
 import javax.validation.executable.ExecutableValidator;
 
-import org.springframework.beans.factory.config.BeanDefinition;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnResource;
 import org.springframework.boot.bind.RelaxedPropertyResolver;
-import org.springframework.boot.validation.MessageInterpolatorFactory;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
-import org.springframework.context.annotation.Role;
+import org.springframework.context.annotation.Import;
 import org.springframework.core.env.Environment;
-import org.springframework.validation.beanvalidation.LocalValidatorFactoryBean;
 import org.springframework.validation.beanvalidation.MethodValidationPostProcessor;
 
 /**
@@ -43,19 +41,12 @@ import org.springframework.validation.beanvalidation.MethodValidationPostProcess
 @Configuration
 @ConditionalOnClass(ExecutableValidator.class)
 @ConditionalOnResource(resources = "classpath:META-INF/services/javax.validation.spi.ValidationProvider")
+@Import({ DefaultValidatorConfiguration.class,
+		Jsr303ValidatorAdapterConfiguration.class })
 public class ValidationAutoConfiguration {
 
 	@Bean
-	@Role(BeanDefinition.ROLE_INFRASTRUCTURE)
+	@ConditionalOnBean(Validator.class)
-	@ConditionalOnMissingBean
-	public static Validator jsr303Validator() {
-		LocalValidatorFactoryBean factoryBean = new LocalValidatorFactoryBean();
-		MessageInterpolatorFactory interpolatorFactory = new MessageInterpolatorFactory();
-		factoryBean.setMessageInterpolator(interpolatorFactory.getObject());
-		return factoryBean;
-	}
-
-	@Bean
 	@ConditionalOnMissingBean
 	public static MethodValidationPostProcessor methodValidationPostProcessor(
 			Environment environment, Validator validator) {

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/WebMvcAutoConfiguration.java

@@ -30,11 +30,21 @@ import javax.servlet.http.HttpServletRequest;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 
+import org.springframework.beans.BeansException;
 import org.springframework.beans.factory.BeanFactory;
+import org.springframework.beans.factory.BeanFactoryUtils;
+import org.springframework.beans.factory.DisposableBean;
+import org.springframework.beans.factory.InitializingBean;
 import org.springframework.beans.factory.ListableBeanFactory;
 import org.springframework.beans.factory.NoSuchBeanDefinitionException;
 import org.springframework.beans.factory.ObjectProvider;
 import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.beans.factory.config.BeanDefinition;
+import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
+import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
+import org.springframework.beans.factory.support.BeanDefinitionRegistry;
+import org.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor;
+import org.springframework.beans.factory.support.RootBeanDefinition;
 import org.springframework.boot.autoconfigure.AutoConfigureAfter;
 import org.springframework.boot.autoconfigure.AutoConfigureOrder;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
@@ -43,27 +53,38 @@ import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication;
+import org.springframework.boot.autoconfigure.validation.DelegatingValidator;
 import org.springframework.boot.autoconfigure.validation.ValidationAutoConfiguration;
 import org.springframework.boot.autoconfigure.web.ResourceProperties.Strategy;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.boot.web.filter.OrderedHiddenHttpMethodFilter;
 import org.springframework.boot.web.filter.OrderedHttpPutFormContentFilter;
 import org.springframework.boot.web.filter.OrderedRequestContextFilter;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.ApplicationContextAware;
 import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.ConditionContext;
+import org.springframework.context.annotation.Conditional;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.ConfigurationCondition;
 import org.springframework.context.annotation.Import;
 import org.springframework.context.annotation.Primary;
+import org.springframework.context.annotation.Role;
 import org.springframework.core.Ordered;
+import org.springframework.core.annotation.Order;
 import org.springframework.core.convert.converter.Converter;
 import org.springframework.core.convert.converter.GenericConverter;
 import org.springframework.core.io.Resource;
+import org.springframework.core.type.AnnotatedTypeMetadata;
 import org.springframework.format.Formatter;
 import org.springframework.format.FormatterRegistry;
 import org.springframework.format.datetime.DateFormatter;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.MediaType;
 import org.springframework.http.converter.HttpMessageConverter;
+import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
+import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
 import org.springframework.validation.DefaultMessageCodesResolver;
 import org.springframework.validation.MessageCodesResolver;
@@ -142,6 +163,12 @@ public class WebMvcAutoConfiguration {
 	public static final String SKIP_PATH_EXTENSION_CONTENT_NEGOTIATION_ATTRIBUTE = PathExtensionContentNegotiationStrategy.class
 			.getName() + ".SKIP";
 
+	@Bean
+	@Role(BeanDefinition.ROLE_INFRASTRUCTURE)
+	public static MvcValidatorPostProcessor mvcValidatorAliasPostProcessor() {
+		return new MvcValidatorPostProcessor();
+	}
+
 	@Bean
 	@ConditionalOnMissingBean(HiddenHttpMethodFilter.class)
 	public OrderedHiddenHttpMethodFilter hiddenHttpMethodFilter() {
@@ -367,21 +394,22 @@ public class WebMvcAutoConfiguration {
 	 * Configuration equivalent to {@code @EnableWebMvc}.
 	 */
 	@Configuration
-	public static class EnableWebMvcConfiguration extends DelegatingWebMvcConfiguration {
+	public static class EnableWebMvcConfiguration extends DelegatingWebMvcConfiguration
+			implements InitializingBean {
 
 		private final WebMvcProperties mvcProperties;
 
-		private final ListableBeanFactory beanFactory;
+		private final ApplicationContext context;
 
 		private final WebMvcRegistrations mvcRegistrations;
 
 		public EnableWebMvcConfiguration(
 				ObjectProvider<WebMvcProperties> mvcPropertiesProvider,
 				ObjectProvider<WebMvcRegistrations> mvcRegistrationsProvider,
-				ListableBeanFactory beanFactory) {
+				ApplicationContext context) {
 			this.mvcProperties = mvcPropertiesProvider.getIfAvailable();
 			this.mvcRegistrations = mvcRegistrationsProvider.getIfUnique();
-			this.beanFactory = beanFactory;
+			this.context = context;
 		}
 
 		@Bean
@@ -412,12 +440,9 @@ public class WebMvcAutoConfiguration {
 
 		@Bean
 		@Override
+		@Conditional(DisableMvcValidatorCondition.class)
 		public Validator mvcValidator() {
-			if (!ClassUtils.isPresent("javax.validation.Validator",
+			return this.context.getBean("mvcValidator", Validator.class);
-					getClass().getClassLoader())) {
-				return super.mvcValidator();
-			}
-			return WebMvcValidator.get(getApplicationContext(), getValidator());
 		}
 
 		@Override
@@ -432,7 +457,7 @@ public class WebMvcAutoConfiguration {
 		@Override
 		protected ConfigurableWebBindingInitializer getConfigurableWebBindingInitializer() {
 			try {
-				return this.beanFactory.getBean(ConfigurableWebBindingInitializer.class);
+				return this.context.getBean(ConfigurableWebBindingInitializer.class);
 			}
 			catch (NoSuchBeanDefinitionException ex) {
 				return super.getConfigurableWebBindingInitializer();
@@ -481,6 +506,15 @@ public class WebMvcAutoConfiguration {
 			return manager;
 		}
 
+		@Override
+		public void afterPropertiesSet() throws Exception {
+			Assert.state(getValidator() == null,
+					"Found unexpected validator configuration. A Spring Boot MVC "
+							+ "validator should be registered as bean named "
+							+ "'mvcValidator' and not returned from "
+							+ "WebMvcConfigurer.getValidator()");
+		}
+
 	}
 
 	@Configuration
@@ -606,4 +640,128 @@ public class WebMvcAutoConfiguration {
 
 	}
 
+	/**
+	 * Condition used to disable the default MVC validator registration. The
+	 * {@link MvcValidatorPostProcessor} is used to configure the {@code mvcValidator}
+	 * bean.
+	 */
+	static class DisableMvcValidatorCondition implements ConfigurationCondition {
+
+		@Override
+		public ConfigurationPhase getConfigurationPhase() {
+			return ConfigurationPhase.REGISTER_BEAN;
+		}
+
+		@Override
+		public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
+			return false;
+		}
+
+	}
+
+	/**
+	 * {@link BeanFactoryPostProcessor} to deal with the MVC validator bean registration.
+	 * Applies the following rules:
+	 * <ul>
+	 * <li>With no validators - Uses standard
+	 * {@link WebMvcConfigurationSupport#mvcValidator()} logic.</li>
+	 * <li>With a single validator - Uses an alias.</li>
+	 * <li>With multiple validators - Registers a mvcValidator bean if not already
+	 * defined.</li>
+	 * </ul>
+	 */
+	@Order(Ordered.LOWEST_PRECEDENCE)
+	static class MvcValidatorPostProcessor
+			implements BeanDefinitionRegistryPostProcessor {
+
+		private static final String JSR303_VALIDATOR_CLASS = "javax.validation.Validator";
+
+		@Override
+		public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry)
+				throws BeansException {
+			if (registry instanceof ListableBeanFactory) {
+				postProcess(registry, (ListableBeanFactory) registry);
+			}
+		}
+
+		@Override
+		public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory)
+				throws BeansException {
+		}
+
+		private void postProcess(BeanDefinitionRegistry registry,
+				ListableBeanFactory beanFactory) {
+			String[] validatorBeans = BeanFactoryUtils.beanNamesForTypeIncludingAncestors(
+					beanFactory, Validator.class, false, false);
+			if (validatorBeans.length == 0) {
+				registerMvcValidator(registry, beanFactory);
+			}
+			else if (validatorBeans.length == 1) {
+				registry.registerAlias(validatorBeans[0], "mvcValidator");
+			}
+			else {
+				if (!ObjectUtils.containsElement(validatorBeans, "mvcValidator")) {
+					registerMvcValidator(registry, beanFactory);
+				}
+			}
+		}
+
+		private void registerMvcValidator(BeanDefinitionRegistry registry,
+				ListableBeanFactory beanFactory) {
+			RootBeanDefinition definition = new RootBeanDefinition();
+			definition.setBeanClass(getClass());
+			definition.setFactoryMethodName("mvcValidator");
+			registry.registerBeanDefinition("mvcValidator", definition);
+		}
+
+		static Validator mvcValidator() {
+			Validator validator = new WebMvcConfigurationSupport().mvcValidator();
+			try {
+				if (ClassUtils.forName(JSR303_VALIDATOR_CLASS, null)
+						.isInstance(validator)) {
+					return new DelegatingWebMvcValidator(validator);
+				}
+			}
+			catch (Exception ex) {
+			}
+			return validator;
+		}
+
+	}
+
+	/**
+	 * {@link DelegatingValidator} for the MVC validator.
+	 */
+	static class DelegatingWebMvcValidator extends DelegatingValidator
+			implements ApplicationContextAware, InitializingBean, DisposableBean {
+
+		public DelegatingWebMvcValidator(Validator targetValidator) {
+			super(targetValidator);
+		}
+
+		@Override
+		public void setApplicationContext(ApplicationContext applicationContext)
+				throws BeansException {
+			if (getDelegate() instanceof ApplicationContextAware) {
+				((ApplicationContextAware) getDelegate())
+						.setApplicationContext(applicationContext);
+			}
+		}
+
+		@Override
+		public void afterPropertiesSet() throws Exception {
+			if (getDelegate() instanceof InitializingBean) {
+				((InitializingBean) getDelegate()).afterPropertiesSet();
+			}
+		}
+
+		@Override
+		public void destroy() throws Exception {
+			if (getDelegate() instanceof DisposableBean) {
+				((DisposableBean) getDelegate()).destroy();
+			}
+		}
+
+	}
+
 }

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/WebMvcValidator.java

@@ -1,144 +0,0 @@
-/*
- * Copyright 2012-2017 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.
- * 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.boot.autoconfigure.web;
-
-import org.springframework.beans.BeansException;
-import org.springframework.beans.factory.DisposableBean;
-import org.springframework.beans.factory.InitializingBean;
-import org.springframework.beans.factory.NoSuchBeanDefinitionException;
-import org.springframework.boot.validation.MessageInterpolatorFactory;
-import org.springframework.context.ApplicationContext;
-import org.springframework.context.ApplicationContextAware;
-import org.springframework.validation.Errors;
-import org.springframework.validation.SmartValidator;
-import org.springframework.validation.Validator;
-import org.springframework.validation.beanvalidation.OptionalValidatorFactoryBean;
-import org.springframework.validation.beanvalidation.SpringValidatorAdapter;
-
-/**
- * A {@link SmartValidator} exposed as a bean for WebMvc use. Wraps existing
- * {@link SpringValidatorAdapter} instances so that only the Spring's {@link Validator}
- * type is exposed. This prevents such a bean to expose both the Spring and JSR-303
- * validator contract at the same time.
- *
- * @author Stephane Nicoll
- * @author Phillip Webb
- */
-class WebMvcValidator implements SmartValidator, ApplicationContextAware,
-		InitializingBean, DisposableBean {
-
-	private final SpringValidatorAdapter target;
-
-	private final boolean existingBean;
-
-	WebMvcValidator(SpringValidatorAdapter target, boolean existingBean) {
-		this.target = target;
-		this.existingBean = existingBean;
-	}
-
-	SpringValidatorAdapter getTarget() {
-		return this.target;
-	}
-
-	@Override
-	public boolean supports(Class<?> clazz) {
-		return this.target.supports(clazz);
-	}
-
-	@Override
-	public void validate(Object target, Errors errors) {
-		this.target.validate(target, errors);
-	}
-
-	@Override
-	public void validate(Object target, Errors errors, Object... validationHints) {
-		this.target.validate(target, errors, validationHints);
-	}
-
-	@Override
-	public void setApplicationContext(ApplicationContext applicationContext)
-			throws BeansException {
-		if (!this.existingBean && this.target instanceof ApplicationContextAware) {
-			((ApplicationContextAware) this.target)
-					.setApplicationContext(applicationContext);
-		}
-	}
-
-	@Override
-	public void afterPropertiesSet() throws Exception {
-		if (!this.existingBean && this.target instanceof InitializingBean) {
-			((InitializingBean) this.target).afterPropertiesSet();
-		}
-	}
-
-	@Override
-	public void destroy() throws Exception {
-		if (!this.existingBean && this.target instanceof DisposableBean) {
-			((DisposableBean) this.target).destroy();
-		}
-	}
-
-	public static Validator get(ApplicationContext applicationContext,
-			Validator validator) {
-		if (validator != null) {
-			return wrap(validator, false);
-		}
-		return getExistingOrCreate(applicationContext);
-	}
-
-	private static Validator getExistingOrCreate(ApplicationContext applicationContext) {
-		Validator existing = getExisting(applicationContext);
-		if (existing != null) {
-			return wrap(existing, true);
-		}
-		return create();
-	}
-
-	private static Validator getExisting(ApplicationContext applicationContext) {
-		try {
-			javax.validation.Validator validator = applicationContext
-					.getBean(javax.validation.Validator.class);
-			if (validator instanceof Validator) {
-				return (Validator) validator;
-			}
-			return new SpringValidatorAdapter(validator);
-		}
-		catch (NoSuchBeanDefinitionException ex) {
-			return null;
-		}
-	}
-
-	private static Validator create() {
-		OptionalValidatorFactoryBean validator = new OptionalValidatorFactoryBean();
-		validator.setMessageInterpolator(new MessageInterpolatorFactory().getObject());
-		return wrap(validator, false);
-	}
-
-	private static Validator wrap(Validator validator, boolean existingBean) {
-		if (validator instanceof javax.validation.Validator) {
-			if (validator instanceof SpringValidatorAdapter) {
-				return new WebMvcValidator((SpringValidatorAdapter) validator,
-						existingBean);
-			}
-			return new WebMvcValidator(
-					new SpringValidatorAdapter((javax.validation.Validator) validator),
-					existingBean);
-		}
-		return validator;
-	}
-
-}

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/security/SpringBootWebSecurityConfigurationTests.java

@@ -31,6 +31,7 @@ import org.junit.Test;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.context.PropertyPlaceholderAutoConfiguration;
+import org.springframework.boot.autoconfigure.validation.ValidationAutoConfiguration;
 import org.springframework.boot.autoconfigure.web.DispatcherServletAutoConfiguration;
 import org.springframework.boot.autoconfigure.web.EmbeddedServletContainerAutoConfiguration;
 import org.springframework.boot.autoconfigure.web.ErrorMvcAutoConfiguration;
@@ -324,9 +325,9 @@ public class SpringBootWebSecurityConfigurationTests {
 	@Documented
 	@Import({ EmbeddedServletContainerAutoConfiguration.class,
 			ServerPropertiesAutoConfiguration.class,
-			DispatcherServletAutoConfiguration.class, WebMvcAutoConfiguration.class,
+			DispatcherServletAutoConfiguration.class, ValidationAutoConfiguration.class,
-			HttpMessageConvertersAutoConfiguration.class, ErrorMvcAutoConfiguration.class,
+			WebMvcAutoConfiguration.class, HttpMessageConvertersAutoConfiguration.class,
-			PropertyPlaceholderAutoConfiguration.class })
+			ErrorMvcAutoConfiguration.class, PropertyPlaceholderAutoConfiguration.class })
 	protected @interface MinimalWebConfiguration {
 
 	}

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/validation/DelegatingValidatorTests.java

@@ -0,0 +1,117 @@
+/*
+ * Copyright 2012-2017 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.
+ * 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.boot.autoconfigure.validation;
+
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+
+import org.springframework.validation.BeanPropertyBindingResult;
+import org.springframework.validation.Errors;
+import org.springframework.validation.SmartValidator;
+import org.springframework.validation.Validator;
+
+import static org.mockito.Matchers.any;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+
+/**
+ * Tests for {@link DelegatingValidator}.
+ *
+ * @author Phillip Webb
+ */
+public class DelegatingValidatorTests {
+
+	@Rule
+	public ExpectedException thrown = ExpectedException.none();
+
+	@Mock
+	private SmartValidator delegate;
+
+	private DelegatingValidator delegating;
+
+	@Before
+	public void setup() {
+		MockitoAnnotations.initMocks(this);
+		this.delegating = new DelegatingValidator(this.delegate);
+	}
+
+	@Test
+	public void createWhenJsrValidatorIsNullShouldThrowException() throws Exception {
+		this.thrown.expect(IllegalArgumentException.class);
+		this.thrown.expectMessage("Target Validator must not be null");
+		new DelegatingValidator((javax.validation.Validator) null);
+	}
+
+	@Test
+	public void createWithJsrValidatorShouldAdapt() throws Exception {
+		javax.validation.Validator delegate = mock(javax.validation.Validator.class);
+		Validator delegating = new DelegatingValidator(delegate);
+		Object target = new Object();
+		Errors errors = new BeanPropertyBindingResult(target, "foo");
+		delegating.validate(target, errors);
+		verify(delegate).validate(any());
+	}
+
+	@Test
+	public void createWithSpringValidatorWhenValidatorIsNullShouldThrowException()
+			throws Exception {
+		this.thrown.expect(IllegalArgumentException.class);
+		this.thrown.expectMessage("Target Validator must not be null");
+		new DelegatingValidator((Validator) null);
+	}
+
+	@Test
+	public void supportsShouldDelegateToValidator() throws Exception {
+		this.delegating.supports(Object.class);
+		verify(this.delegate).supports(Object.class);
+	}
+
+	@Test
+	public void validateShouldDelegateToValidator() throws Exception {
+		Object target = new Object();
+		Errors errors = new BeanPropertyBindingResult(target, "foo");
+		this.delegating.validate(target, errors);
+		verify(this.delegate).validate(target, errors);
+	}
+
+	@Test
+	public void validateWithHintsShouldDelegateToValidator() throws Exception {
+		Object target = new Object();
+		Errors errors = new BeanPropertyBindingResult(target, "foo");
+		Object[] hints = { "foo", "bar" };
+		this.delegating.validate(target, errors, hints);
+		verify(this.delegate).validate(target, errors, hints);
+		;
+	}
+
+	@Test
+	public void validateWithHintsWhenDelegateIsNotSmartShouldDelegateToSimpleValidator()
+			throws Exception {
+		Validator delegate = mock(Validator.class);
+		DelegatingValidator delegating = new DelegatingValidator(delegate);
+		Object target = new Object();
+		Errors errors = new BeanPropertyBindingResult(target, "foo");
+		Object[] hints = { "foo", "bar" };
+		delegating.validate(target, errors, hints);
+		verify(delegate).validate(target, errors);
+	}
+
+}

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/validation/ValidationAutoConfigurationTests.java

@@ -32,9 +32,12 @@ import org.springframework.context.annotation.AnnotationConfigApplicationContext
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.validation.annotation.Validated;
+import org.springframework.validation.beanvalidation.LocalValidatorFactoryBean;
 import org.springframework.validation.beanvalidation.MethodValidationPostProcessor;
+import org.springframework.validation.beanvalidation.OptionalValidatorFactoryBean;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.mock;
 
 /**
  * Tests for {@link ValidationAutoConfiguration}.
@@ -56,45 +59,94 @@ public class ValidationAutoConfigurationTests {
 	}
 
 	@Test
-	public void validationIsEnabled() {
+	public void validationAutoConfigurationShouldConfigureJsrAndSpringValidator()
-		load(SampleService.class);
+			throws Exception {
+		load(Config.class);
+		Validator jsrValidator = this.context.getBean(Validator.class);
+		String[] jsrValidatorNames = this.context.getBeanNamesForType(Validator.class);
+		org.springframework.validation.Validator springValidator = this.context
+				.getBean(org.springframework.validation.Validator.class);
+		String[] springValidatorNames = this.context
+				.getBeanNamesForType(org.springframework.validation.Validator.class);
+		assertThat(jsrValidator).isInstanceOf(LocalValidatorFactoryBean.class);
+		assertThat(jsrValidator).isEqualTo(springValidator);
+		assertThat(jsrValidatorNames).containsExactly("defaultValidator");
+		assertThat(springValidatorNames).containsExactly("defaultValidator");
+	}
+
+	@Test
+	public void validationAutoConfigurationWhenUserProvidesValidatorShouldBackOff()
+			throws Exception {
+		load(UserDefinedValidatorConfig.class);
+		Validator jsrValidator = this.context.getBean(Validator.class);
+		String[] jsrValidatorNames = this.context.getBeanNamesForType(Validator.class);
+		org.springframework.validation.Validator springValidator = this.context
+				.getBean(org.springframework.validation.Validator.class);
+		String[] springValidatorNames = this.context
+				.getBeanNamesForType(org.springframework.validation.Validator.class);
+		assertThat(jsrValidator).isInstanceOf(OptionalValidatorFactoryBean.class);
+		assertThat(jsrValidator).isEqualTo(springValidator);
+		assertThat(jsrValidatorNames).containsExactly("customValidator");
+		assertThat(springValidatorNames).containsExactly("customValidator");
+	}
+
+	@Test
+	public void validationAutoConfigurationWhenUserProvidesJsrOnlyShouldAdaptIt()
+			throws Exception {
+		load(UserDefinedJsrValidatorConfig.class);
+		Validator jsrValidator = this.context.getBean(Validator.class);
+		String[] jsrValidatorNames = this.context.getBeanNamesForType(Validator.class);
+		org.springframework.validation.Validator springValidator = this.context
+				.getBean(org.springframework.validation.Validator.class);
+		String[] springValidatorNames = this.context
+				.getBeanNamesForType(org.springframework.validation.Validator.class);
+		assertThat(jsrValidator).isNotEqualTo(springValidator);
+		assertThat(springValidator).isInstanceOf(DelegatingValidator.class);
+		assertThat(jsrValidatorNames).containsExactly("customValidator");
+		assertThat(springValidatorNames).containsExactly("jsr303ValidatorAdapter");
+	}
+
+	@Test
+	public void validationAutoConfigurationShouldBeEnabled() {
+		load(ClassWithConstraint.class);
 		assertThat(this.context.getBeansOfType(Validator.class)).hasSize(1);
-		SampleService service = this.context.getBean(SampleService.class);
+		ClassWithConstraint service = this.context.getBean(ClassWithConstraint.class);
-		service.doSomething("Valid");
+		service.call("Valid");
 		this.thrown.expect(ConstraintViolationException.class);
-		service.doSomething("KO");
+		service.call("KO");
 	}
 
 	@Test
-	public void validationUsesCglibProxy() {
+	public void validationAutoConfigurationShouldUseCglibProxy() {
-		load(DefaultAnotherSampleService.class);
+		load(ImplementationOfInterfaceWithConstraint.class);
 		assertThat(this.context.getBeansOfType(Validator.class)).hasSize(1);
-		DefaultAnotherSampleService service = this.context
+		ImplementationOfInterfaceWithConstraint service = this.context
-				.getBean(DefaultAnotherSampleService.class);
+				.getBean(ImplementationOfInterfaceWithConstraint.class);
-		service.doSomething(42);
+		service.call(42);
 		this.thrown.expect(ConstraintViolationException.class);
-		service.doSomething(2);
+		service.call(2);
 	}
 
 	@Test
-	public void validationCanBeConfiguredToUseJdkProxy() {
+	public void validationAutoConfigurationWhenProxyTargetClassIsFalseShouldUseJdkProxy() {
 		load(AnotherSampleServiceConfiguration.class,
 				"spring.aop.proxy-target-class=false");
 		assertThat(this.context.getBeansOfType(Validator.class)).hasSize(1);
-		assertThat(this.context.getBeansOfType(DefaultAnotherSampleService.class))
+		assertThat(this.context
-				.isEmpty();
+				.getBeansOfType(ImplementationOfInterfaceWithConstraint.class)).isEmpty();
-		AnotherSampleService service = this.context.getBean(AnotherSampleService.class);
+		InterfaceWithConstraint service = this.context
-		service.doSomething(42);
+				.getBean(InterfaceWithConstraint.class);
+		service.call(42);
 		this.thrown.expect(ConstraintViolationException.class);
-		service.doSomething(2);
+		service.call(2);
 	}
 
 	@Test
-	public void userDefinedMethodValidationPostProcessorTakesPrecedence() {
+	public void validationAutoConfigurationWhenUserDefinesMethodValidationPostProcessorShouldBackOff() {
-		load(SampleConfiguration.class);
+		load(UserDefinedMethodValidationConfig.class);
 		assertThat(this.context.getBeansOfType(Validator.class)).hasSize(1);
 		Object userMethodValidationPostProcessor = this.context
-				.getBean("testMethodValidationPostProcessor");
+				.getBean("customMethodValidationPostProcessor");
 		assertThat(this.context.getBean(MethodValidationPostProcessor.class))
 				.isSameAs(userMethodValidationPostProcessor);
 		assertThat(this.context.getBeansOfType(MethodValidationPostProcessor.class))
@@ -115,47 +167,73 @@ public class ValidationAutoConfigurationTests {
 		this.context = ctx;
 	}
 
-	@Validated
+	@Configuration
-	static class SampleService {
+	static class Config {
 
-		public void doSomething(@Size(min = 3, max = 10) String name) {
+	}
+
+	@Configuration
+	static class UserDefinedValidatorConfig {
 
+		@Bean
+		public OptionalValidatorFactoryBean customValidator() {
+			return new OptionalValidatorFactoryBean();
 		}
 
 	}
 
-	interface AnotherSampleService {
+	@Configuration
+	static class UserDefinedJsrValidatorConfig {
+
+		@Bean
+		public Validator customValidator() {
+			return mock(Validator.class);
+		}
 
-		void doSomething(@Min(42) Integer counter);
 	}
 
-	@Validated
+	@Configuration
-	static class DefaultAnotherSampleService implements AnotherSampleService {
+	static class UserDefinedMethodValidationConfig {
-
-		@Override
-		public void doSomething(Integer counter) {
 
+		@Bean
+		public MethodValidationPostProcessor customMethodValidationPostProcessor() {
+			return new MethodValidationPostProcessor();
 		}
+
 	}
 
 	@Configuration
 	static class AnotherSampleServiceConfiguration {
 
 		@Bean
-		public AnotherSampleService anotherSampleService() {
+		public InterfaceWithConstraint implementationOfInterfaceWithConstraint() {
-			return new DefaultAnotherSampleService();
+			return new ImplementationOfInterfaceWithConstraint();
 		}
 
 	}
 
-	@Configuration
+	@Validated
-	static class SampleConfiguration {
+	static class ClassWithConstraint {
+
+		public void call(@Size(min = 3, max = 10) String name) {
 
-		@Bean
-		public MethodValidationPostProcessor testMethodValidationPostProcessor() {
-			return new MethodValidationPostProcessor();
 		}
 
 	}
 
+	interface InterfaceWithConstraint {
+
+		void call(@Min(42) Integer counter);
+	}
+
+	@Validated
+	static class ImplementationOfInterfaceWithConstraint
+			implements InterfaceWithConstraint {
+
+		@Override
+		public void call(Integer counter) {
+
+		}
+	}
+
 }

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/BasicErrorControllerDirectMockMvcTests.java

@@ -35,6 +35,7 @@ import org.junit.rules.ExpectedException;
 
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.context.PropertyPlaceholderAutoConfiguration;
+import org.springframework.boot.autoconfigure.validation.ValidationAutoConfiguration;
 import org.springframework.boot.builder.SpringApplicationBuilder;
 import org.springframework.boot.test.util.ApplicationContextTestUtils;
 import org.springframework.context.annotation.Configuration;
@@ -126,9 +127,9 @@ public class BasicErrorControllerDirectMockMvcTests {
 	@Documented
 	@Import({ EmbeddedServletContainerAutoConfiguration.class,
 			ServerPropertiesAutoConfiguration.class,
-			DispatcherServletAutoConfiguration.class, WebMvcAutoConfiguration.class,
+			DispatcherServletAutoConfiguration.class, ValidationAutoConfiguration.class,
-			HttpMessageConvertersAutoConfiguration.class, ErrorMvcAutoConfiguration.class,
+			WebMvcAutoConfiguration.class, HttpMessageConvertersAutoConfiguration.class,
-			PropertyPlaceholderAutoConfiguration.class })
+			ErrorMvcAutoConfiguration.class, PropertyPlaceholderAutoConfiguration.class })
 	protected @interface MinimalWebConfiguration {
 
 	}

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/BasicErrorControllerMockMvcTests.java

@@ -35,6 +35,7 @@ import org.junit.runner.RunWith;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.context.PropertyPlaceholderAutoConfiguration;
+import org.springframework.boot.autoconfigure.validation.ValidationAutoConfiguration;
 import org.springframework.boot.test.context.SpringBootTest;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
@@ -128,9 +129,9 @@ public class BasicErrorControllerMockMvcTests {
 	@Import({ EmbeddedServletContainerAutoConfiguration.EmbeddedTomcat.class,
 			EmbeddedServletContainerAutoConfiguration.class,
 			ServerPropertiesAutoConfiguration.class,
-			DispatcherServletAutoConfiguration.class, WebMvcAutoConfiguration.class,
+			DispatcherServletAutoConfiguration.class, ValidationAutoConfiguration.class,
-			HttpMessageConvertersAutoConfiguration.class, ErrorMvcAutoConfiguration.class,
+			WebMvcAutoConfiguration.class, HttpMessageConvertersAutoConfiguration.class,
-			PropertyPlaceholderAutoConfiguration.class })
+			ErrorMvcAutoConfiguration.class, PropertyPlaceholderAutoConfiguration.class })
 	protected @interface MinimalWebConfiguration {
 
 	}

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/WebMvcAutoConfigurationTests.java

@@ -27,7 +27,6 @@ import java.util.Map;
 
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
-import javax.validation.ValidatorFactory;
 
 import org.assertj.core.api.Condition;
 import org.joda.time.DateTime;
@@ -37,8 +36,11 @@ import org.junit.Test;
 import org.junit.rules.ExpectedException;
 
 import org.springframework.beans.DirectFieldAccessor;
+import org.springframework.beans.factory.BeanCreationException;
 import org.springframework.beans.factory.NoSuchBeanDefinitionException;
 import org.springframework.boot.autoconfigure.context.PropertyPlaceholderAutoConfiguration;
+import org.springframework.boot.autoconfigure.validation.DelegatingValidator;
+import org.springframework.boot.autoconfigure.validation.ValidationAutoConfiguration;
 import org.springframework.boot.autoconfigure.web.WebMvcAutoConfiguration.WebMvcAutoConfigurationAdapter;
 import org.springframework.boot.autoconfigure.web.WebMvcAutoConfiguration.WelcomePageHandlerMapping;
 import org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext;
@@ -59,11 +61,11 @@ import org.springframework.mock.web.MockHttpServletRequest;
 import org.springframework.test.util.ReflectionTestUtils;
 import org.springframework.test.web.servlet.MockMvc;
 import org.springframework.test.web.servlet.setup.MockMvcBuilders;
+import org.springframework.util.ObjectUtils;
 import org.springframework.util.ReflectionUtils;
 import org.springframework.util.StringUtils;
 import org.springframework.validation.Validator;
 import org.springframework.validation.beanvalidation.LocalValidatorFactoryBean;
-import org.springframework.validation.beanvalidation.SpringValidatorAdapter;
 import org.springframework.web.accept.ContentNegotiationManager;
 import org.springframework.web.bind.support.ConfigurableWebBindingInitializer;
 import org.springframework.web.filter.HttpPutFormContentFilter;
@@ -655,77 +657,154 @@ public class WebMvcAutoConfigurationTests {
 	}
 
 	@Test
-	public void validationNoJsr303ValidatorExposedByDefault() {
+	public void validatorWhenSuppliedByConfigurerShouldThrowException() throws Exception {
+		this.thrown.expect(BeanCreationException.class);
+		this.thrown.expectMessage("unexpected validator configuration");
+		load(ValidatorWebMvcConfigurer.class);
+	}
+
+	@Test
+	public void validatorWhenAutoConfiguredShouldUseAlias() throws Exception {
 		load();
-		assertThat(this.context.getBeansOfType(ValidatorFactory.class)).isEmpty();
+		Object defaultValidator = this.context.getBean("defaultValidator");
-		assertThat(this.context.getBeansOfType(javax.validation.Validator.class))
+		Object mvcValidator = this.context.getBean("mvcValidator");
-				.isEmpty();
+		String[] jsrValidatorBeans = this.context
-		assertThat(this.context.getBeansOfType(Validator.class)).hasSize(1);
+				.getBeanNamesForType(javax.validation.Validator.class);
+		String[] springValidatorBeans = this.context.getBeanNamesForType(Validator.class);
+		assertThat(mvcValidator).isSameAs(defaultValidator);
+		assertThat(springValidatorBeans).containsExactly("defaultValidator");
+		assertThat(jsrValidatorBeans).containsExactly("defaultValidator");
 	}
 
 	@Test
-	public void validationCustomConfigurerTakesPrecedence() {
+	public void validatorWhenUserDefinedSpringOnlyShouldUseDefined() throws Exception {
-		load(MvcValidator.class);
+		load(UserDefinedSpringOnlyValidator.class);
-		assertThat(this.context.getBeansOfType(ValidatorFactory.class)).isEmpty();
+		Object customValidator = this.context.getBean("customValidator");
-		assertThat(this.context.getBeansOfType(javax.validation.Validator.class))
+		Object mvcValidator = this.context.getBean("mvcValidator");
-				.isEmpty();
+		String[] jsrValidatorBeans = this.context
-		assertThat(this.context.getBeansOfType(Validator.class)).hasSize(1);
+				.getBeanNamesForType(javax.validation.Validator.class);
-		Validator validator = this.context.getBean(Validator.class);
+		String[] springValidatorBeans = this.context.getBeanNamesForType(Validator.class);
-		assertThat(validator)
+		assertThat(mvcValidator).isSameAs(customValidator);
-				.isSameAs(this.context.getBean(MvcValidator.class).validator);
+		assertThat(this.context.getBean(Validator.class)).isEqualTo(customValidator);
+		assertThat(springValidatorBeans).containsExactly("customValidator");
+		assertThat(jsrValidatorBeans).isEmpty();
 	}
 
 	@Test
-	public void validationCustomConfigurerTakesPrecedenceAndDoNotExposeJsr303() {
+	public void validatorWhenUserDefinedJsr303ShouldAdapt() throws Exception {
-		load(MvcJsr303Validator.class);
+		load(UserDefinedJsr303Validator.class);
-		assertThat(this.context.getBeansOfType(ValidatorFactory.class)).isEmpty();
+		Object customValidator = this.context.getBean("customValidator");
-		assertThat(this.context.getBeansOfType(javax.validation.Validator.class))
+		Object mvcValidator = this.context.getBean("mvcValidator");
-				.isEmpty();
+		String[] jsrValidatorBeans = this.context
-		assertThat(this.context.getBeansOfType(Validator.class)).hasSize(1);
+				.getBeanNamesForType(javax.validation.Validator.class);
-		Validator validator = this.context.getBean(Validator.class);
+		String[] springValidatorBeans = this.context.getBeanNamesForType(Validator.class);
-		assertThat(validator).isInstanceOf(WebMvcValidator.class);
+		assertThat(mvcValidator).isNotSameAs(customValidator);
-		assertThat(((WebMvcValidator) validator).getTarget())
+		assertThat(this.context.getBean(javax.validation.Validator.class))
-				.isSameAs(this.context.getBean(MvcJsr303Validator.class).validator);
+				.isEqualTo(customValidator);
+		assertThat(springValidatorBeans).containsExactly("jsr303ValidatorAdapter");
+		assertThat(jsrValidatorBeans).containsExactly("customValidator");
 	}
 
 	@Test
-	public void validationJsr303CustomValidatorReusedAsSpringValidator() {
+	public void validatorWhenUserDefinedSingleJsr303AndSpringShouldUseDefined()
-		load(CustomValidator.class);
+			throws Exception {
-		assertThat(this.context.getBeansOfType(ValidatorFactory.class)).hasSize(1);
+		load(UserDefinedSingleJsr303AndSpringValidator.class);
-		assertThat(this.context.getBeansOfType(javax.validation.Validator.class))
+		Object customValidator = this.context.getBean("customValidator");
-				.hasSize(1);
+		Object mvcValidator = this.context.getBean("mvcValidator");
-		assertThat(this.context.getBeansOfType(Validator.class)).hasSize(2);
+		String[] jsrValidatorBeans = this.context
-		Validator validator = this.context.getBean("mvcValidator", Validator.class);
+				.getBeanNamesForType(javax.validation.Validator.class);
-		assertThat(validator).isInstanceOf(WebMvcValidator.class);
+		String[] springValidatorBeans = this.context.getBeanNamesForType(Validator.class);
-		assertThat(((WebMvcValidator) validator).getTarget())
+		assertThat(mvcValidator).isSameAs(customValidator);
-				.isSameAs(this.context.getBean(javax.validation.Validator.class));
+		assertThat(this.context.getBean(javax.validation.Validator.class))
+				.isEqualTo(customValidator);
+		assertThat(this.context.getBean(Validator.class)).isEqualTo(customValidator);
+		assertThat(springValidatorBeans).containsExactly("customValidator");
+		assertThat(jsrValidatorBeans).containsExactly("customValidator");
 	}
 
 	@Test
-	public void validationJsr303ValidatorExposedAsSpringValidator() {
+	public void validatorWhenUserDefinedJsr303AndSpringShouldUseDefined()
-		load(Jsr303Validator.class);
+			throws Exception {
-		assertThat(this.context.getBeansOfType(ValidatorFactory.class)).isEmpty();
+		load(UserDefinedJsr303AndSpringValidator.class);
-		assertThat(this.context.getBeansOfType(javax.validation.Validator.class))
+		Object customJsrValidator = this.context.getBean("customJsrValidator");
-				.hasSize(1);
+		Object customSpringValidator = this.context.getBean("customSpringValidator");
-		assertThat(this.context.getBeansOfType(Validator.class)).hasSize(1);
+		Object mvcValidator = this.context.getBean("mvcValidator");
-		Validator validator = this.context.getBean(Validator.class);
+		String[] jsrValidatorBeans = this.context
-		assertThat(validator).isInstanceOf(WebMvcValidator.class);
+				.getBeanNamesForType(javax.validation.Validator.class);
-		SpringValidatorAdapter target = ((WebMvcValidator) validator)
+		String[] springValidatorBeans = this.context.getBeanNamesForType(Validator.class);
-				.getTarget();
+		assertThat(customJsrValidator).isNotSameAs(customSpringValidator);
-		assertThat(new DirectFieldAccessor(target).getPropertyValue("targetValidator"))
+		assertThat(mvcValidator).isSameAs(customSpringValidator);
-				.isSameAs(this.context.getBean(javax.validation.Validator.class));
+		assertThat(this.context.getBean(javax.validation.Validator.class))
+				.isEqualTo(customJsrValidator);
+		assertThat(this.context.getBean(Validator.class))
+				.isEqualTo(customSpringValidator);
+		assertThat(springValidatorBeans).containsExactly("customSpringValidator");
+		assertThat(jsrValidatorBeans).containsExactly("customJsrValidator");
+	}
+
+	@Test
+	public void validatorWhenExcludingValidatorAutoConfigurationShouldUseMvc()
+			throws Exception {
+		load(null, new Class[] { ValidationAutoConfiguration.class });
+		Object mvcValidator = this.context.getBean("mvcValidator");
+		String[] jsrValidatorBeans = this.context
+				.getBeanNamesForType(javax.validation.Validator.class);
+		String[] springValidatorBeans = this.context.getBeanNamesForType(Validator.class);
+		assertThat(mvcValidator).isInstanceOf(DelegatingValidator.class);
+		assertThat(springValidatorBeans).containsExactly("mvcValidator");
+		assertThat(jsrValidatorBeans).isEmpty();
+	}
+
+	@Test
+	public void validatorWhenMultipleValidatorsAndNoMvcValidatorShouldAddMvc()
+			throws Exception {
+		load(MultipleValidatorsAndNoMvcValidator.class);
+		Object customValidator1 = this.context.getBean("customValidator1");
+		Object customValidator2 = this.context.getBean("customValidator2");
+		Object mvcValidator = this.context.getBean("mvcValidator");
+		String[] jsrValidatorBeans = this.context
+				.getBeanNamesForType(javax.validation.Validator.class);
+		String[] springValidatorBeans = this.context.getBeanNamesForType(Validator.class);
+		assertThat(mvcValidator).isNotSameAs(customValidator1)
+				.isNotSameAs(customValidator2);
+		assertThat(springValidatorBeans).containsExactly("customValidator1",
+				"customValidator2", "mvcValidator");
+		assertThat(jsrValidatorBeans).isEmpty();
+	}
+
+	@Test
+	public void validatorWhenMultipleValidatorsAndMvcValidatorShouldUseMvc()
+			throws Exception {
+		load(MultipleValidatorsAndMvcValidator.class);
+		Object customValidator = this.context.getBean("customValidator");
+		Object mvcValidator = this.context.getBean("mvcValidator");
+		String[] jsrValidatorBeans = this.context
+				.getBeanNamesForType(javax.validation.Validator.class);
+		String[] springValidatorBeans = this.context.getBeanNamesForType(Validator.class);
+		assertThat(mvcValidator).isNotSameAs(customValidator);
+		assertThat(springValidatorBeans).containsExactly("customValidator",
+				"mvcValidator");
+		assertThat(jsrValidatorBeans).isEmpty();
 	}
 
 	private void load(Class<?> config, String... environment) {
+		load(config, null, environment);
+	}
+
+	private void load(Class<?> config, Class<?>[] exclude, String... environment) {
 		this.context = new AnnotationConfigEmbeddedWebApplicationContext();
 		EnvironmentTestUtils.addEnvironment(this.context, environment);
 		List<Class<?>> configClasses = new ArrayList<Class<?>>();
 		if (config != null) {
 			configClasses.add(config);
 		}
-		configClasses.addAll(Arrays.asList(Config.class, WebMvcAutoConfiguration.class,
+		configClasses.addAll(Arrays.asList(Config.class,
+				ValidationAutoConfiguration.class, WebMvcAutoConfiguration.class,
 				HttpMessageConvertersAutoConfiguration.class,
 				PropertyPlaceholderAutoConfiguration.class));
+		if (!ObjectUtils.isEmpty(exclude)) {
+			configClasses.removeAll(Arrays.asList(exclude));
+		}
 		this.context.register(configClasses.toArray(new Class<?>[configClasses.size()]));
 		this.context.refresh();
 	}
@@ -895,45 +974,86 @@ public class WebMvcAutoConfigurationTests {
 	}
 
 	@Configuration
-	protected static class MvcValidator extends WebMvcConfigurerAdapter {
+	protected static class ValidatorWebMvcConfigurer extends WebMvcConfigurerAdapter {
-
-		private final Validator validator = mock(Validator.class);
 
 		@Override
 		public Validator getValidator() {
-			return this.validator;
+			return mock(Validator.class);
 		}
 
 	}
 
 	@Configuration
-	protected static class MvcJsr303Validator extends WebMvcConfigurerAdapter {
+	static class UserDefinedSpringOnlyValidator {
 
-		private final LocalValidatorFactoryBean validator = new LocalValidatorFactoryBean();
+		@Bean
+		public Validator customValidator() {
+			return mock(Validator.class);
+		}
 
-		@Override
+	}
-		public Validator getValidator() {
+
-			return this.validator;
+	@Configuration
+	static class UserDefinedJsr303Validator {
+
+		@Bean
+		public javax.validation.Validator customValidator() {
+			return mock(javax.validation.Validator.class);
 		}
 
 	}
 
 	@Configuration
-	static class Jsr303Validator {
+	static class UserDefinedSingleJsr303AndSpringValidator {
 
 		@Bean
-		public javax.validation.Validator jsr303Validator() {
+		public LocalValidatorFactoryBean customValidator() {
+			return new LocalValidatorFactoryBean();
+		}
+
+	}
+
+	@Configuration
+	static class UserDefinedJsr303AndSpringValidator {
+
+		@Bean
+		public javax.validation.Validator customJsrValidator() {
 			return mock(javax.validation.Validator.class);
 		}
 
+		@Bean
+		public Validator customSpringValidator() {
+			return mock(Validator.class);
+		}
+
 	}
 
 	@Configuration
-	static class CustomValidator {
+	static class MultipleValidatorsAndNoMvcValidator {
+
+		@Bean
+		public Validator customValidator1() {
+			return mock(Validator.class);
+		}
+
+		@Bean
+		public Validator customValidator2() {
+			return mock(Validator.class);
+		}
+
+	}
+
+	@Configuration
+	static class MultipleValidatorsAndMvcValidator {
 
 		@Bean
 		public Validator customValidator() {
-			return new LocalValidatorFactoryBean();
+			return mock(Validator.class);
+		}
+
+		@Bean
+		public Validator mvcValidator() {
+			return mock(Validator.class);
 		}
 
 	}

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/WebMvcValidatorTests.java

@@ -1,152 +0,0 @@
-/*
- * Copyright 2012-2017 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.
- * 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.boot.autoconfigure.web;
-
-import java.util.HashMap;
-
-import javax.validation.constraints.Min;
-
-import org.junit.After;
-import org.junit.Test;
-
-import org.springframework.context.ApplicationContext;
-import org.springframework.context.annotation.AnnotationConfigApplicationContext;
-import org.springframework.context.annotation.Bean;
-import org.springframework.context.annotation.Configuration;
-import org.springframework.validation.MapBindingResult;
-import org.springframework.validation.beanvalidation.LocalValidatorFactoryBean;
-
-import static org.assertj.core.api.Assertions.assertThat;
-import static org.mockito.Matchers.any;
-import static org.mockito.Mockito.mock;
-import static org.mockito.Mockito.times;
-import static org.mockito.Mockito.verify;
-
-/**
- * Tests for {@link WebMvcValidator}.
- *
- * @author Stephane Nicoll
- */
-public class WebMvcValidatorTests {
-
-	private AnnotationConfigApplicationContext context;
-
-	@After
-	public void close() {
-		if (this.context != null) {
-			this.context.close();
-		}
-	}
-
-	@Test
-	public void wrapLocalValidatorFactoryBean() {
-		WebMvcValidator wrapper = load(
-				LocalValidatorFactoryBeanConfig.class);
-		assertThat(wrapper.supports(SampleData.class)).isTrue();
-		MapBindingResult errors = new MapBindingResult(new HashMap<String, Object>(),
-				"test");
-		wrapper.validate(new SampleData(40), errors);
-		assertThat(errors.getErrorCount()).isEqualTo(1);
-	}
-
-	@Test
-	public void wrapperInvokesCallbackOnNonManagedBean() {
-		load(NonManagedBeanConfig.class);
-		LocalValidatorFactoryBean validator = this.context
-				.getBean(NonManagedBeanConfig.class).validator;
-		verify(validator, times(1)).setApplicationContext(any(ApplicationContext.class));
-		verify(validator, times(1)).afterPropertiesSet();
-		verify(validator, times(0)).destroy();
-		this.context.close();
-		this.context = null;
-		verify(validator, times(1)).destroy();
-	}
-
-	@Test
-	public void wrapperDoesNotInvokeCallbackOnManagedBean() {
-		load(ManagedBeanConfig.class);
-		LocalValidatorFactoryBean validator = this.context
-				.getBean(ManagedBeanConfig.class).validator;
-		verify(validator, times(0)).setApplicationContext(any(ApplicationContext.class));
-		verify(validator, times(0)).afterPropertiesSet();
-		verify(validator, times(0)).destroy();
-		this.context.close();
-		this.context = null;
-		verify(validator, times(0)).destroy();
-	}
-
-	private WebMvcValidator load(Class<?> config) {
-		AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext();
-		ctx.register(config);
-		ctx.refresh();
-		this.context = ctx;
-		return this.context.getBean(WebMvcValidator.class);
-	}
-
-	@Configuration
-	static class LocalValidatorFactoryBeanConfig {
-
-		@Bean
-		public LocalValidatorFactoryBean validator() {
-			return new LocalValidatorFactoryBean();
-		}
-
-		@Bean
-		public WebMvcValidator wrapper() {
-			return new WebMvcValidator(validator(), true);
-		}
-
-	}
-
-	@Configuration
-	static class NonManagedBeanConfig {
-
-		private final LocalValidatorFactoryBean validator = mock(
-				LocalValidatorFactoryBean.class);
-
-		@Bean
-		public WebMvcValidator wrapper() {
-			return new WebMvcValidator(this.validator, false);
-		}
-
-	}
-
-	@Configuration
-	static class ManagedBeanConfig {
-
-		private final LocalValidatorFactoryBean validator = mock(
-				LocalValidatorFactoryBean.class);
-
-		@Bean
-		public WebMvcValidator wrapper() {
-			return new WebMvcValidator(this.validator, true);
-		}
-
-	}
-
-	static class SampleData {
-
-		@Min(42)
-		private int counter;
-
-		SampleData(int counter) {
-			this.counter = counter;
-		}
-
-	}
-
-}