Add @NestedConfigurationProperty meta-data support

Add a @NestedConfigurationProperty annotation which can be used to
customize how configuration mete-data is generated.

Prior to this commit only inner-classes where considered nested
(see Tomcat in ServerProperties). Using this new annotation, the Ssl
property in ServerProperties can be detected as well.

See gh-1001

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

@@ -38,6 +38,7 @@ import org.springframework.boot.context.embedded.tomcat.TomcatConnectorCustomize
 import org.springframework.boot.context.embedded.tomcat.TomcatContextCustomizer;
 import org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainerFactory;
 import org.springframework.boot.context.properties.ConfigurationProperties;
+import org.springframework.boot.context.properties.NestedConfigurationProperty;
 import org.springframework.util.StringUtils;
 
 /**
@@ -60,6 +61,7 @@ public class ServerProperties implements EmbeddedServletContainerCustomizer {
 
 	private String contextPath;
 
+	@NestedConfigurationProperty
 	private Ssl ssl;
 
 	@NotNull

spring-boot-tools/spring-boot-configuration-processor/src/main/java/org/springframework/boot/configurationprocessor/ConfigurationMetadataAnnotationProcessor.java

@@ -64,6 +64,9 @@ public class ConfigurationMetadataAnnotationProcessor extends AbstractProcessor
 	static final String CONFIGURATION_PROPERTIES_ANNOTATION = "org.springframework.boot."
 			+ "context.properties.ConfigurationProperties";
 
+	static final String NESTED_CONFIGURATION_PROPERTY_ANNOTATION = "org.springframework.boot."
+			+ "context.properties.NestedConfigurationProperty";
+
 	private ConfigurationMetadata metadata;
 
 	private TypeUtils typeUtils;
@@ -74,6 +77,10 @@ public class ConfigurationMetadataAnnotationProcessor extends AbstractProcessor
 		return CONFIGURATION_PROPERTIES_ANNOTATION;
 	}
 
+	protected String nestedConfigurationPropertyAnnotation() {
+		return NESTED_CONFIGURATION_PROPERTY_ANNOTATION;
+	}
+
 	@Override
 	public synchronized void init(ProcessingEnvironment env) {
 		super.init(env);
@@ -166,8 +173,11 @@ public class ConfigurationMetadataAnnotationProcessor extends AbstractProcessor
 			ExecutableElement getter = entry.getValue();
 			ExecutableElement setter = members.getPublicSetters().get(name);
 			VariableElement field = members.getFields().get(name);
-			if (setter != null
-					|| this.typeUtils.isCollectionOrMap(getter.getReturnType())) {
+			boolean isNested = getAnnotation(field,
+					nestedConfigurationPropertyAnnotation()) != null;
+			boolean isCollection = this.typeUtils.isCollectionOrMap(getter
+					.getReturnType());
+			if (!isNested && (setter != null || isCollection)) {
 				String dataType = this.typeUtils.getType(getter.getReturnType());
 				String sourceType = this.typeUtils.getType(element);
 				String description = this.typeUtils.getJavaDoc(field);
@@ -182,17 +192,21 @@ public class ConfigurationMetadataAnnotationProcessor extends AbstractProcessor
 			TypeElementMembers members) {
 		for (Map.Entry<String, ExecutableElement> entry : members.getPublicGetters()
 				.entrySet()) {
+			String name = entry.getKey();
 			ExecutableElement getter = entry.getValue();
+			VariableElement field = members.getFields().get(name);
 			Element returnType = this.processingEnv.getTypeUtils().asElement(
 					getter.getReturnType());
 			AnnotationMirror annotation = getAnnotation(getter,
 					configurationPropertiesAnnotation());
+			boolean isNested = getAnnotation(field,
+					nestedConfigurationPropertyAnnotation()) != null;
 			if (returnType != null && returnType instanceof TypeElement
 					&& annotation == null) {
 				TypeElement returns = (TypeElement) returnType;
-				if (this.typeUtils.isEnclosedIn(returnType, element)) {
-					String nestedPrefix = ConfigurationMetadata.nestedPrefix(prefix,
-							entry.getKey());
+				if (this.typeUtils.isEnclosedIn(returnType, element) || isNested) {
+					String nestedPrefix = ConfigurationMetadata
+							.nestedPrefix(prefix, name);
 					this.metadata.add(ItemMetadata.newGroup(nestedPrefix,
 							this.typeUtils.getType(returns),
 							this.typeUtils.getType(element), getter.toString()));
@@ -203,9 +217,11 @@ public class ConfigurationMetadataAnnotationProcessor extends AbstractProcessor
 	}
 
 	private AnnotationMirror getAnnotation(Element element, String type) {
-		for (AnnotationMirror annotation : element.getAnnotationMirrors()) {
-			if (type.equals(annotation.getAnnotationType().toString())) {
-				return annotation;
+		if (element != null) {
+			for (AnnotationMirror annotation : element.getAnnotationMirrors()) {
+				if (type.equals(annotation.getAnnotationType().toString())) {
+					return annotation;
+				}
 			}
 		}
 		return null;

spring-boot-tools/spring-boot-configuration-processor/src/test/java/org/springframework/boot/configurationprocessor/ConfigurationMetadataAnnotationProcessorTests.java

@@ -39,6 +39,7 @@ import org.springframework.boot.configurationsample.simple.SimpleTypeProperties;
 import org.springframework.boot.configurationsample.specific.InnerClassAnnotatedGetterConfig;
 import org.springframework.boot.configurationsample.specific.InnerClassProperties;
 import org.springframework.boot.configurationsample.specific.InnerClassRootConfig;
+import org.springframework.boot.configurationsample.specific.SimplePojo;
 
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.not;
@@ -238,11 +239,8 @@ public class ConfigurationMetadataAnnotationProcessorTests {
 						.fromSource(InnerClassProperties.class));
 		assertThat(metadata, containsProperty("config.the-second.name"));
 		assertThat(metadata, containsProperty("config.the-second.bar.name"));
-		assertThat(
-				metadata,
-				containsGroup("config.third").ofType(
-						InnerClassProperties.SimplePojo.class).fromSource(
-						InnerClassProperties.class));
+		assertThat(metadata, containsGroup("config.third").ofType(SimplePojo.class)
+				.fromSource(InnerClassProperties.class));
 		assertThat(metadata, containsProperty("config.third.value"));
 	}
 
@@ -267,6 +265,8 @@ public class ConfigurationMetadataAnnotationProcessorTests {
 
 		static final String CONFIGURATION_PROPERTIES_ANNOTATION = "org.springframework.boot.configurationsample.ConfigurationProperties";
 
+		static final String NESTED_CONFIGURATION_PROPERTY_ANNOTATION = "org.springframework.boot.configurationsample.NestedConfigurationProperty";
+
 		private ConfigurationMetadata metadata;
 
 		@Override
@@ -274,6 +274,11 @@ public class ConfigurationMetadataAnnotationProcessorTests {
 			return CONFIGURATION_PROPERTIES_ANNOTATION;
 		}
 
+		@Override
+		protected String nestedConfigurationPropertyAnnotation() {
+			return NESTED_CONFIGURATION_PROPERTY_ANNOTATION;
+		}
+
 		@Override
 		protected void writeMetaData(ConfigurationMetadata metadata) {
 			this.metadata = metadata;

spring-boot-tools/spring-boot-configuration-processor/src/test/java/org/springframework/boot/configurationsample/NestedConfigurationProperty.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2012-2014 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.configurationsample;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Alternative to Spring Boot's {@code @NestedConfigurationProperty} for testing (removes
+ * the need for a dependency on the real annotation).
+ *
+ * @author Stephane Nicoll
+ * @author Phillip Webb
+ * @since 1.2.0
+ */
+@Target(ElementType.FIELD)
+@Retention(RetentionPolicy.RUNTIME)
+@Documented
+public @interface NestedConfigurationProperty {
+
+}

spring-boot-tools/spring-boot-configuration-processor/src/test/java/org/springframework/boot/configurationsample/specific/InnerClassProperties.java

@@ -17,6 +17,7 @@
 package org.springframework.boot.configurationsample.specific;
 
 import org.springframework.boot.configurationsample.ConfigurationProperties;
+import org.springframework.boot.configurationsample.NestedConfigurationProperty;
 
 /**
  * Demonstrate the auto-detection of a inner config classes.
@@ -30,6 +31,7 @@ public class InnerClassProperties {
 
 	private Foo second = new Foo();
 
+	@NestedConfigurationProperty
 	private final SimplePojo third = new SimplePojo();
 
 	public Foo getFirst() {
@@ -81,9 +83,4 @@ public class InnerClassProperties {
 
 	}
 
-	public static class SimplePojo extends
-			org.springframework.boot.configurationsample.specific.SimplePojo {
-
-	}
-
 }

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

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2012-2014 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;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Indicates that a field in a {@link ConfigurationProperties} object should be treated as
+ * if it were a nested type. This annotation has no bearing on the actual binding
+ * processes, but it is used by the {@code spring-boot-configuration-processor} as a hint
+ * that a field is not bound as a single value.
+ *
+ * @author Stephane Nicoll
+ * @author Phillip Webb
+ * @since 1.2.0
+ */
+@Target(ElementType.FIELD)
+@Retention(RetentionPolicy.RUNTIME)
+@Documented
+public @interface NestedConfigurationProperty {
+
+}