Ensure that `@ConfigurationProperties` is mandatory

Previously it was possible to bind a bean to the root prefix by just
adding `@EnableConfigurationProperties` with the class of said bean.

 This use case is misleading and prevents any meta-data to be generated
 for that object since the annotation processor reacts on the presence of
 the `@ConfigurationProperties` annotation.

 If a class is included in the list of configuration properties bean to
 create via the `@EnableConfigurationProperties` annotation we now make
 sure that the `@configurationProperties` annotation is present on it.

 Closes gh-3460

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

@@ -42,7 +42,6 @@ import org.springframework.boot.autoconfigure.template.TemplateAvailabilityProvi
 import org.springframework.boot.context.embedded.ConfigurableEmbeddedServletContainer;
 import org.springframework.boot.context.embedded.EmbeddedServletContainerCustomizer;
 import org.springframework.boot.context.embedded.ErrorPage;
-import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.ConditionContext;
 import org.springframework.context.annotation.Conditional;
@@ -74,7 +73,6 @@ import org.springframework.web.util.HtmlUtils;
 // Ensure this loads before the main WebMvcAutoConfiguration so that the error View is
 // available
 @AutoConfigureBefore(WebMvcAutoConfiguration.class)
-@EnableConfigurationProperties(ErrorProperties.class)
 @Configuration
 public class ErrorMvcAutoConfiguration {
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2014 the original author or authors.
+ * Copyright 2012-2015 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.
@@ -32,6 +32,7 @@ import java.lang.annotation.Target;
  *
  * @author Dave Syer
  * @see ConfigurationPropertiesBindingPostProcessor
+ * @see EnableConfigurationProperties
  */
 @Target({ ElementType.TYPE, ElementType.METHOD })
 @Retention(RetentionPolicy.RUNTIME)

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

@@ -269,7 +269,7 @@ public class ConfigurationPropertiesBindingPostProcessor implements BeanPostProc
 			throws BeansException {
 		ConfigurationProperties annotation = AnnotationUtils
 				.findAnnotation(bean.getClass(), ConfigurationProperties.class);
-		if (annotation != null || bean instanceof ConfigurationPropertiesHolder) {
+		if (annotation != null) {
 			postProcessBeforeInitialization(bean, beanName, annotation);
 		}
 		annotation = this.beans.findFactoryAnnotation(beanName,
@@ -288,8 +288,7 @@ public class ConfigurationPropertiesBindingPostProcessor implements BeanPostProc
 
 	private void postProcessBeforeInitialization(Object bean, String beanName,
 			ConfigurationProperties annotation) {
-		Object target = (bean instanceof ConfigurationPropertiesHolder
-				? ((ConfigurationPropertiesHolder) bean).getTarget() : bean);
+		Object target = bean;
 		PropertiesConfigurationFactory<Object> factory = new PropertiesConfigurationFactory<Object>(
 				target);
 		if (annotation != null && annotation.locations().length != 0) {

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

@@ -1,37 +0,0 @@
-/*
- * Copyright 2012-2013 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.context.properties;
-
-/**
- * Properties holder registered by {@link EnableConfigurationPropertiesImportSelector} to
- * be picked up by {@link ConfigurationPropertiesBindingPostProcessor}.
- *
- * @author Dave Syer
- */
-class ConfigurationPropertiesHolder {
-
-	private final Object target;
-
-	ConfigurationPropertiesHolder(Object target) {
-		this.target = target;
-	}
-
-	public Object getTarget() {
-		return this.target;
-	}
-
-}

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

@@ -40,9 +40,10 @@ import org.springframework.context.annotation.Import;
 public @interface EnableConfigurationProperties {
 
 	/**
-	 * Convenient way to quickly register {@link ConfigurationProperties} beans with
-	 * Spring. Standard Spring Beans will also be scanned regardless of this value.
-	 * @return {@link ConfigurationProperties} beans to register
+	 * Convenient way to quickly register {@link ConfigurationProperties} annotated
+	 * beans with Spring. Standard Spring Beans will also be scanned regardless of
+	 * this value.
+	 * @return {@link ConfigurationProperties} annotated beans to register
 	 */
 	Class<?>[] value() default {};
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2014 the original author or authors.
+ * Copyright 2012-2015 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.
@@ -26,6 +26,7 @@ import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
 import org.springframework.context.annotation.ImportSelector;
 import org.springframework.core.annotation.AnnotationUtils;
 import org.springframework.core.type.AnnotationMetadata;
+import org.springframework.util.Assert;
 import org.springframework.util.MultiValueMap;
 import org.springframework.util.StringUtils;
 
@@ -41,6 +42,7 @@ import org.springframework.util.StringUtils;
  *
  * @author Dave Syer
  * @author Christian Dupuis
+ * @author Stephane Nicoll
  */
 class EnableConfigurationPropertiesImportSelector implements ImportSelector {
 
@@ -113,18 +115,8 @@ class EnableConfigurationPropertiesImportSelector implements ImportSelector {
 
 			ConfigurationProperties properties = AnnotationUtils.findAnnotation(type,
 					ConfigurationProperties.class);
-			if (properties == null) {
-				registerPropertiesHolder(registry, name);
-			}
-		}
-
-		private void registerPropertiesHolder(BeanDefinitionRegistry registry,
-				String name) {
-			BeanDefinitionBuilder builder = BeanDefinitionBuilder
-					.genericBeanDefinition(ConfigurationPropertiesHolder.class);
-			builder.addConstructorArgReference(name);
-			registry.registerBeanDefinition(name + ".HOLDER",
-					builder.getBeanDefinition());
+			Assert.notNull(properties, "No " + ConfigurationProperties.class.getSimpleName()
+					+ " annotation found on  '" + type.getName() + "'.");
 		}
 
 	}

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

@@ -286,6 +286,17 @@ public class ConfigurationPropertiesBindingPostProcessorTests {
 				.getValue(), equalTo("test1"));
 	}
 
+	@Test
+	public void bindWithoutConfigurationPropertiesAnnotation() {
+		this.context = new AnnotationConfigApplicationContext();
+		EnvironmentTestUtils.addEnvironment(this.context, "name:foo");
+		this.context.register(ConfigurationPropertiesWithoutAnnotation.class);
+
+		this.thrown.expect(IllegalArgumentException.class);
+		this.thrown.expectMessage("No ConfigurationProperties annotation found");
+		this.context.refresh();
+	}
+
 	private void assertBindingFailure(int errorCount) {
 		try {
 			this.context.refresh();
@@ -666,4 +677,24 @@ public class ConfigurationPropertiesBindingPostProcessorTests {
 
 	}
 
+	@Configuration
+	@EnableConfigurationProperties(PropertyWithoutConfigurationPropertiesAnnotation.class)
+	public static class ConfigurationPropertiesWithoutAnnotation {
+
+
+	}
+
+	public static class PropertyWithoutConfigurationPropertiesAnnotation {
+
+		private String name;
+
+		public String getName() {
+			return this.name;
+		}
+
+		public void setName(String name) {
+			this.name = name;
+		}
+	}
+
 }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2014 the original author or authors.
+ * Copyright 2012-2015 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.
@@ -47,13 +47,14 @@ import static org.junit.Assert.assertNotNull;
  * Tests for {@link EnableConfigurationProperties}.
  *
  * @author Dave Syer
+ * @author Stephane Nicoll
  */
 public class EnableConfigurationPropertiesTests {
 
 	private final AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
 
 	@Rule
-	public ExpectedException expected = ExpectedException.none();
+	public ExpectedException thrown = ExpectedException.none();
 
 	@After
 	public void close() {
@@ -158,7 +159,7 @@ public class EnableConfigurationPropertiesTests {
 	public void testExceptionOnValidation() {
 		this.context.register(ExceptionIfInvalidTestConfiguration.class);
 		EnvironmentTestUtils.addEnvironment(this.context, "name:foo");
-		this.expected.expectCause(Matchers.<Throwable>instanceOf(BindException.class));
+		this.thrown.expectCause(Matchers.<Throwable>instanceOf(BindException.class));
 		this.context.refresh();
 	}
 
@@ -211,6 +212,16 @@ public class EnableConfigurationPropertiesTests {
 
 	@Test
 	public void testPropertiesBindingWithoutAnnotation() {
+		this.context.register(InvalidConfiguration.class);
+		EnvironmentTestUtils.addEnvironment(this.context, "name:foo");
+
+		this.thrown.expect(IllegalArgumentException.class);
+		this.thrown.expectMessage("No ConfigurationProperties annotation found");
+		this.context.refresh();
+	}
+
+	@Test
+	public void testPropertiesBindingWithoutAnnotationValue() {
 		this.context.register(MoreConfiguration.class);
 		EnvironmentTestUtils.addEnvironment(this.context, "name:foo");
 		this.context.refresh();
@@ -548,6 +559,13 @@ public class EnableConfigurationPropertiesTests {
 	protected static class MoreConfiguration {
 	}
 
+
+	@Configuration
+	@EnableConfigurationProperties(InvalidConfiguration.class)
+	protected static class InvalidConfiguration {
+	}
+
+
 	@ConfigurationProperties
 	protected static class NestedProperties {
 
@@ -662,6 +680,7 @@ public class EnableConfigurationPropertiesTests {
 
 	}
 
+	@ConfigurationProperties
 	protected static class MoreProperties {
 
 		private String name;
@@ -673,6 +692,20 @@ public class EnableConfigurationPropertiesTests {
 		// No getter - you should be able to bind to a write-only bean
 	}
 
+	// No annotation
+	protected static class InvalidProperties {
+
+		private String name;
+
+		public String getName() {
+			return this.name;
+		}
+
+		public void setName(String name) {
+			this.name = name;
+		}
+	}
+
 	@ConfigurationProperties(locations = "${binding.location:classpath:name.yml}")
 	protected static class ResourceBindingProperties {