Detected candidate inner classes

This commit improves the indexer to also consider static inner classes
on top of regular top level classes.

Issue: SPR-16112

Author: snicoll

spring-context-indexer/src/main/java/org/springframework/context/index/CandidateComponentsIndexer.java

@@ -19,6 +19,7 @@
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Collections;
+import java.util.EnumSet;
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Set;
@@ -29,7 +30,9 @@
 import javax.lang.model.SourceVersion;
 import javax.lang.model.element.AnnotationMirror;
 import javax.lang.model.element.Element;
+import javax.lang.model.element.ElementKind;
 import javax.lang.model.element.ExecutableElement;
+import javax.lang.model.element.Modifier;
 import javax.lang.model.element.TypeElement;
 
 /**
@@ -42,6 +45,10 @@
  */
 public class CandidateComponentsIndexer implements Processor {
 
+	private static final Set<ElementKind> TYPE_KINDS =
+			Collections.unmodifiableSet(EnumSet.of(ElementKind.CLASS,
+					ElementKind.INTERFACE));
+
 	private MetadataStore metadataStore;
 
 	private MetadataCollector metadataCollector;
@@ -102,6 +109,11 @@ private List<StereotypesProvider> getStereotypesProviders(ProcessingEnvironment
 	}
 
 	private void processElement(Element element) {
+		addMetadataFor(element);
+		staticTypesIn(element.getEnclosedElements()).forEach(this::processElement);
+	}
+
+	private void addMetadataFor(Element element) {
 		Set<String> stereotypes = new LinkedHashSet<>();
 		this.stereotypesProviders.forEach(p -> stereotypes.addAll(p.getStereotypes(element)));
 		if (!stereotypes.isEmpty()) {
@@ -121,4 +133,14 @@ private void writeMetaData() {
 		}
 	}
 
+	private static List<TypeElement> staticTypesIn(Iterable<? extends Element> elements) {
+		List<TypeElement> list = new ArrayList<>();
+		for (Element e : elements) {
+			if (TYPE_KINDS.contains(e.getKind())
+					&& e.getModifiers().contains(Modifier.STATIC))
+				list.add(TypeElement.class.cast(e));
+		}
+		return list;
+	}
+
 }

spring-context-indexer/src/test/java/org/springframework/context/index/CandidateComponentsIndexerTests.java

@@ -38,13 +38,15 @@
 import org.springframework.context.index.sample.SampleController;
 import org.springframework.context.index.sample.SampleMetaController;
 import org.springframework.context.index.sample.SampleMetaIndexedController;
+import org.springframework.context.index.sample.SampleNonStaticEmbedded;
 import org.springframework.context.index.sample.SampleNone;
 import org.springframework.context.index.sample.SampleRepository;
 import org.springframework.context.index.sample.SampleService;
 import org.springframework.context.index.sample.cdi.SampleManagedBean;
 import org.springframework.context.index.sample.cdi.SampleNamed;
 import org.springframework.context.index.sample.jpa.SampleConverter;
 import org.springframework.context.index.sample.jpa.SampleEmbeddable;
+import org.springframework.context.index.sample.SampleEmbedded;
 import org.springframework.context.index.sample.jpa.SampleEntity;
 import org.springframework.context.index.sample.jpa.SampleMappedSuperClass;
 import org.springframework.context.index.sample.type.Repo;
@@ -55,6 +57,7 @@
 import org.springframework.context.index.sample.type.SpecializedRepo;
 import org.springframework.context.index.test.TestCompiler;
 import org.springframework.stereotype.Component;
+import org.springframework.util.ClassUtils;
 
 import static org.hamcrest.Matchers.*;
 import static org.junit.Assert.*;
@@ -198,6 +201,26 @@ public void typeStereotypeOnIndexedInterface() throws IOException {
 		testSingleComponent(Repo.class, Repo.class);
 	}
 
+	@Test
+	public void embeddedCandidatesAreDetected()
+			throws IOException, ClassNotFoundException {
+		// Validate nested type structure
+		String nestedType = "org.springframework.context.index.sample.SampleEmbedded.Another$AnotherPublicCandidate";
+		Class<?> type = ClassUtils.forName(nestedType, getClass().getClassLoader());
+		assertThat(type, sameInstance(SampleEmbedded.Another.AnotherPublicCandidate.class));
+
+		CandidateComponentsMetadata metadata = compile(SampleEmbedded.class);
+		assertThat(metadata, hasComponent(
+				SampleEmbedded.PublicCandidate.class, Component.class));
+		assertThat(metadata, hasComponent(nestedType, Component.class.getName()));
+		assertThat(metadata.getItems(), hasSize(2));
+	}
+
+	@Test
+	public void embeddedNonStaticCandidateAreIgnored() throws IOException {
+		CandidateComponentsMetadata metadata = compile(SampleNonStaticEmbedded.class);
+		assertThat(metadata.getItems(), hasSize(0));
+	}
 
 	private void testComponent(Class<?>... classes) throws IOException {
 		CandidateComponentsMetadata metadata = compile(classes);

spring-context-indexer/src/test/java/org/springframework/context/index/sample/SampleEmbedded.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2002-2017 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.context.index.sample;
+
+import org.springframework.stereotype.Component;
+
+/**
+ * Test candidate for an embedded {@link Component}.
+ *
+ * @author Stephane Nicoll
+ */
+public class SampleEmbedded {
+
+	@Component
+	public static class PublicCandidate {
+
+	}
+
+	public static class Another {
+
+		@Component
+		public static class AnotherPublicCandidate {
+
+		}
+	}
+
+}

spring-context-indexer/src/test/java/org/springframework/context/index/sample/SampleNonStaticEmbedded.java

@@ -0,0 +1,33 @@
+/*
+ * Copyright 2002-2017 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.context.index.sample;
+
+import org.springframework.stereotype.Component;
+
+/**
+ * Candidate with a inner class that isn't static (and should therefore not be added).
+ *
+ * @author Stephane Nicoll
+ */
+public class SampleNonStaticEmbedded {
+
+	@Component
+	public class InvalidCandidate {
+
+	}
+
+}