Use `@Validated` as trigger for JSR-330 validation

Update `ConfigurationPropertiesBindingPostProcessor` so that
`@Validated` is expected to be used to trigger JSR-330 validation.

Any existing configuration classes that use JSR-330 annotations but
don't have `@Validated` will currently still be validated, but will
now log a warning. This should give users a chance to add the requested
annotations before the next Spring Boot release where we will use them
as the exclusive signal that validation is required.

Closes gh-7579

spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc

@@ -1090,13 +1090,16 @@ only rely on custom converters qualified with `@ConfigurationPropertiesBinding`.
 
 [[boot-features-external-config-validation]]
 ==== @ConfigurationProperties Validation
-Spring Boot will attempt to validate external configuration, by default using JSR-303
-(if it is on the classpath). You can simply add JSR-303 `javax.validation` constraint
-annotations to your `@ConfigurationProperties` class:
+Spring Boot will attempt to validate `@ConfigurationProperties` classes whenever they
+annotated with Spring's `@Validated` annotation. You can use JSR-303 `javax.validation`
+constraint annotations directly on your configuration class. Simply ensure that a
+compliant JSR-303 implementation is on your classpath, then add constraint annotations to
+your fields:
 
 [source,java,indent=0]
 ----
 	@ConfigurationProperties(prefix="foo")
+	@Validated
 	public class FooProperties {
 
 		@NotNull
@@ -1114,6 +1117,7 @@ as `@Valid` to trigger its validation. For example, building upon the above
 [source,java,indent=0]
 ----
 	@ConfigurationProperties(prefix="connection")
+	@Validated
 	public class FooProperties {
 
 		@NotNull

spring-boot-samples/spring-boot-sample-simple/pom.xml

@@ -24,6 +24,10 @@
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-starter</artifactId>
 		</dependency>
+		<dependency>
+			<groupId>org.hibernate</groupId>
+			<artifactId>hibernate-validator</artifactId>
+		</dependency>
 		<!-- Test -->
 		<dependency>
 			<groupId>org.springframework.boot</groupId>

spring-boot-samples/spring-boot-sample-simple/src/main/java/sample/simple/SampleConfigurationProperties.java

@@ -0,0 +1,39 @@
+/*
+ * 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 sample.simple;
+
+import javax.validation.constraints.NotNull;
+
+import org.springframework.boot.context.properties.ConfigurationProperties;
+import org.springframework.stereotype.Component;
+
+@Component
+@ConfigurationProperties(prefix = "sample")
+public class SampleConfigurationProperties {
+
+	@NotNull
+	private String name;
+
+	public String getName() {
+		return this.name;
+	}
+
+	public void setName(String name) {
+		this.name = name;
+	}
+
+}

spring-boot-samples/spring-boot-sample-simple/src/main/resources/application.properties

@@ -1 +1,3 @@
-name: Phil
+name=Phil
+sample.name=Andy
+

spring-boot-samples/spring-boot-sample-simple/src/test/java/sample/simple/SampleSimpleApplicationTests.java

@@ -58,6 +58,10 @@ public class SampleSimpleApplicationTests {
 		SampleSimpleApplication.main(new String[0]);
 		String output = this.outputCapture.toString();
 		assertThat(output).contains("Hello Phil");
+		assertThat(output).contains("The @ConfigurationProperties bean class "
+				+ "sample.simple.SampleConfigurationProperties contains "
+				+ "validation constraints but had not been annotated "
+				+ "with @Validated");
 	}
 
 	@Test

spring-boot-samples/spring-boot-sample-simple/src/test/resources/application.properties

@@ -1 +0,0 @@
-name: Phil

spring-boot/src/main/java/org/springframework/boot/bind/PropertiesConfigurationFactory.java

@@ -267,8 +267,9 @@ public class PropertiesConfigurationFactory<T>
 				relaxedTargetNames);
 		dataBinder.bind(propertyValues);
 		if (this.validator != null) {
-			validate(dataBinder);
+			dataBinder.validate();
 		}
+		checkForBindingErrors(dataBinder);
 	}
 
 	private Iterable<String> getRelaxedTargetNames() {
@@ -338,8 +339,8 @@ public class PropertiesConfigurationFactory<T>
 		return this.target != null && Map.class.isAssignableFrom(this.target.getClass());
 	}
 
-	private void validate(RelaxedDataBinder dataBinder) throws BindException {
-		dataBinder.validate();
+	private void checkForBindingErrors(RelaxedDataBinder dataBinder)
+			throws BindException {
 		BindingResult errors = dataBinder.getBindingResult();
 		if (errors.hasErrors()) {
 			logger.error("Properties configuration failed validation");

spring-boot/src/main/java/org/springframework/boot/context/properties/ConfigurationProperties.java

@@ -23,6 +23,7 @@ import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 
 import org.springframework.core.annotation.AliasFor;
+import org.springframework.validation.annotation.Validated;
 
 /**
  * Annotation for externalized configuration. Add this to a class definition or a
@@ -80,9 +81,10 @@ public @interface ConfigurationProperties {
 	boolean ignoreUnknownFields() default true;
 
 	/**
-	 * Flag to indicate that an exception should be raised if a Validator is available and
-	 * validation fails. If it is set to false, validation errors will be swallowed. They
-	 * will be logged, but not propagated to the caller.
+	 * Flag to indicate that an exception should be raised if a Validator is available,
+	 * the class is annotated with {@link Validated @Validated} and validation fails. If
+	 * it is set to false, validation errors will be swallowed. They will be logged, but
+	 * not propagated to the caller.
 	 * @return the flag value (default true)
 	 */
 	boolean exceptionIfInvalid() default true;

spring-boot/src/main/java/org/springframework/boot/context/properties/ConfigurationPropertiesBindingPostProcessor.java

@@ -45,6 +45,7 @@ import org.springframework.context.event.ContextRefreshedEvent;
 import org.springframework.context.support.PropertySourcesPlaceholderConfigurer;
 import org.springframework.core.Ordered;
 import org.springframework.core.PriorityOrdered;
+import org.springframework.core.annotation.AnnotatedElementUtils;
 import org.springframework.core.annotation.AnnotationUtils;
 import org.springframework.core.convert.ConversionService;
 import org.springframework.core.convert.converter.Converter;
@@ -61,6 +62,7 @@ import org.springframework.util.ClassUtils;
 import org.springframework.util.StringUtils;
 import org.springframework.validation.Errors;
 import org.springframework.validation.Validator;
+import org.springframework.validation.annotation.Validated;
 import org.springframework.validation.beanvalidation.LocalValidatorFactoryBean;
 
 /**
@@ -362,8 +364,8 @@ public class ConfigurationPropertiesBindingPostProcessor implements BeanPostProc
 			return this.validator;
 		}
 		if (this.localValidator == null && isJsr303Present()) {
-			this.localValidator = new LocalValidatorFactory()
-					.run(this.applicationContext);
+			this.localValidator = new ValidatedLocalValidatorFactoryBean(
+					this.applicationContext);
 		}
 		return this.localValidator;
 	}
@@ -394,18 +396,38 @@ public class ConfigurationPropertiesBindingPostProcessor implements BeanPostProc
 	}
 
 	/**
-	 * Factory to create JSR 303 LocalValidatorFactoryBean. Inner class to prevent class
-	 * loader issues.
+	 * {@link LocalValidatorFactoryBean} supports classes annotated with
+	 * {@link Validated @Validated}.
 	 */
-	private static class LocalValidatorFactory {
-
-		public Validator run(ApplicationContext applicationContext) {
-			LocalValidatorFactoryBean validator = new LocalValidatorFactoryBean();
-			MessageInterpolatorFactory interpolatorFactory = new MessageInterpolatorFactory();
-			validator.setApplicationContext(applicationContext);
-			validator.setMessageInterpolator(interpolatorFactory.getObject());
-			validator.afterPropertiesSet();
-			return validator;
+	private static class ValidatedLocalValidatorFactoryBean
+			extends LocalValidatorFactoryBean {
+
+		private static final Log logger = LogFactory
+				.getLog(ConfigurationPropertiesBindingPostProcessor.class);
+
+		ValidatedLocalValidatorFactoryBean(ApplicationContext applicationContext) {
+			setApplicationContext(applicationContext);
+			setMessageInterpolator(new MessageInterpolatorFactory().getObject());
+			afterPropertiesSet();
+		}
+
+		@Override
+		public boolean supports(Class<?> type) {
+			if (!super.supports(type)) {
+				return false;
+			}
+			if (AnnotatedElementUtils.isAnnotated(type, Validated.class)) {
+				return true;
+			}
+			if (type.getPackage().getName().startsWith("org.springframework.boot")) {
+				return false;
+			}
+			if (getConstraintsForClass(type).isBeanConstrained()) {
+				logger.warn("The @ConfigurationProperties bean " + type
+						+ " contains validation constraints but had not been annotated "
+						+ "with @Validated.");
+			}
+			return true;
 		}
 
 	}

spring-boot/src/test/java/org/springframework/boot/context/properties/ConfigurationPropertiesBindingPostProcessorTests.java

@@ -46,6 +46,7 @@ import org.springframework.validation.BindException;
 import org.springframework.validation.Errors;
 import org.springframework.validation.ValidationUtils;
 import org.springframework.validation.Validator;
+import org.springframework.validation.annotation.Validated;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.Assert.fail;
@@ -456,6 +457,7 @@ public class ConfigurationPropertiesBindingPostProcessorTests {
 	}
 
 	@ConfigurationProperties(prefix = "test")
+	@Validated
 	public static class PropertyWithJSR303 extends PropertyWithoutJSR303 {
 
 		@NotNull

spring-boot/src/test/java/org/springframework/boot/context/properties/EnableConfigurationPropertiesTests.java

@@ -38,6 +38,7 @@ import org.springframework.core.env.MutablePropertySources;
 import org.springframework.stereotype.Component;
 import org.springframework.test.context.support.TestPropertySourceUtils;
 import org.springframework.validation.BindException;
+import org.springframework.validation.annotation.Validated;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
@@ -172,6 +173,17 @@ public class EnableConfigurationPropertiesTests {
 		this.context.refresh();
 	}
 
+	@Test
+	public void testNoExceptionOnValidationWithoutValidated() {
+		this.context.register(IgnoredIfInvalidButNotValidatedTestConfiguration.class);
+		TestPropertySourceUtils.addInlinedPropertiesToEnvironment(this.context,
+				"name:foo");
+		this.context.refresh();
+		IgnoredIfInvalidButNotValidatedTestProperties bean = this.context
+				.getBean(IgnoredIfInvalidButNotValidatedTestProperties.class);
+		assertThat(bean.getDescription()).isNull();
+	}
+
 	@Test
 	public void testNoExceptionOnValidation() {
 		this.context.register(NoExceptionIfInvalidTestConfiguration.class);
@@ -432,6 +444,12 @@ public class EnableConfigurationPropertiesTests {
 
 	}
 
+	@Configuration
+	@EnableConfigurationProperties(IgnoredIfInvalidButNotValidatedTestProperties.class)
+	protected static class IgnoredIfInvalidButNotValidatedTestConfiguration {
+
+	}
+
 	@Configuration
 	@EnableConfigurationProperties(NoExceptionIfInvalidTestProperties.class)
 	protected static class NoExceptionIfInvalidTestConfiguration {
@@ -658,6 +676,7 @@ public class EnableConfigurationPropertiesTests {
 	}
 
 	@ConfigurationProperties
+	@Validated
 	protected static class ExceptionIfInvalidTestProperties extends TestProperties {
 
 		@NotNull
@@ -673,7 +692,25 @@ public class EnableConfigurationPropertiesTests {
 
 	}
 
+	@ConfigurationProperties
+	protected static class IgnoredIfInvalidButNotValidatedTestProperties
+			extends TestProperties {
+
+		@NotNull
+		private String description;
+
+		public String getDescription() {
+			return this.description;
+		}
+
+		public void setDescription(String description) {
+			this.description = description;
+		}
+
+	}
+
 	@ConfigurationProperties(exceptionIfInvalid = false)
+	@Validated
 	protected static class NoExceptionIfInvalidTestProperties extends TestProperties {
 
 		@NotNull

spring-boot/src/test/java/org/springframework/boot/diagnostics/analyzer/BindFailureAnalyzerTests.java

@@ -32,6 +32,7 @@ import org.springframework.boot.context.properties.EnableConfigurationProperties
 import org.springframework.boot.diagnostics.FailureAnalysis;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 import org.springframework.context.i18n.LocaleContextHolder;
+import org.springframework.validation.annotation.Validated;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
@@ -90,6 +91,7 @@ public class BindFailureAnalyzerTests {
 	}
 
 	@ConfigurationProperties("test.foo")
+	@Validated
 	static class ValidationFailureProperties {
 
 		@NotNull