Add support of declarative use of reflection

This commit adds a `@Reflective` annotation that can be used to declare
that the annotated element requires reflection at runtime. By default,
the annotated element is exposed but this can be customized by
specifying a dedicated `ReflectiveProcessor`.

Closes gh-28469

spring-context/src/test/java/org/springframework/context/aot/ReflectiveProcessorBeanRegistrationAotProcessorTests.java

@@ -0,0 +1,220 @@
+/*
+ * Copyright 2002-2022 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
+ *
+ *      https://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.aot;
+
+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;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.aot.generate.DefaultGenerationContext;
+import org.springframework.aot.generate.GenerationContext;
+import org.springframework.aot.generate.InMemoryGeneratedFiles;
+import org.springframework.aot.hint.MemberCategory;
+import org.springframework.aot.hint.RuntimeHints;
+import org.springframework.aot.hint.TypeReference;
+import org.springframework.aot.hint.annotation.Reflective;
+import org.springframework.beans.factory.aot.BeanRegistrationAotContribution;
+import org.springframework.beans.factory.aot.BeanRegistrationCode;
+import org.springframework.beans.factory.support.DefaultListableBeanFactory;
+import org.springframework.beans.factory.support.RegisteredBean;
+import org.springframework.beans.factory.support.RootBeanDefinition;
+import org.springframework.core.annotation.AliasFor;
+import org.springframework.core.annotation.SynthesizedAnnotation;
+import org.springframework.lang.Nullable;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.mock;
+
+/**
+ * Tests for {@link ReflectiveProcessorBeanRegistrationAotProcessor}.
+ *
+ * @author Stephane Nicoll
+ */
+class ReflectiveProcessorBeanRegistrationAotProcessorTests {
+
+	private final ReflectiveProcessorBeanRegistrationAotProcessor processor = new ReflectiveProcessorBeanRegistrationAotProcessor();
+
+	private final GenerationContext generationContext = new DefaultGenerationContext(
+			new InMemoryGeneratedFiles());
+
+	@Test
+	void shouldIgnoreNonAnnotatedType() {
+		assertThat(createContribution(String.class)).isNull();
+	}
+
+	@Test
+	void shouldProcessAnnotationOnType() {
+		process(SampleTypeAnnotatedBean.class);
+		assertThat(this.generationContext.getRuntimeHints().reflection().getTypeHint(SampleTypeAnnotatedBean.class))
+				.isNotNull();
+	}
+
+	@Test
+	void shouldProcessAnnotationOnConstructor() {
+		process(SampleConstructorAnnotatedBean.class);
+		assertThat(this.generationContext.getRuntimeHints().reflection().getTypeHint(SampleConstructorAnnotatedBean.class))
+				.satisfies(typeHint -> assertThat(typeHint.constructors()).singleElement()
+						.satisfies(constructorHint -> assertThat(constructorHint.getParameterTypes())
+								.containsExactly(TypeReference.of(String.class))));
+	}
+
+	@Test
+	void shouldProcessAnnotationOnField() {
+		process(SampleFieldAnnotatedBean.class);
+		assertThat(this.generationContext.getRuntimeHints().reflection().getTypeHint(SampleFieldAnnotatedBean.class))
+				.satisfies(typeHint -> assertThat(typeHint.fields()).singleElement()
+						.satisfies(fieldHint -> assertThat(fieldHint.getName()).isEqualTo("managed")));
+	}
+
+	@Test
+	void shouldProcessAnnotationOnMethod() {
+		process(SampleMethodAnnotatedBean.class);
+		assertThat(this.generationContext.getRuntimeHints().reflection().getTypeHint(SampleMethodAnnotatedBean.class))
+				.satisfies(typeHint -> assertThat(typeHint.methods()).singleElement()
+						.satisfies(methodHint -> assertThat(methodHint.getName()).isEqualTo("managed")));
+	}
+
+	@Test
+	void shouldRegisterAnnotation() {
+		process(SampleMethodMetaAnnotatedBean.class);
+		RuntimeHints runtimeHints = this.generationContext.getRuntimeHints();
+		assertThat(runtimeHints.reflection().getTypeHint(SampleInvoker.class)).satisfies(typeHint ->
+				assertThat(typeHint.getMemberCategories()).containsOnly(MemberCategory.INVOKE_PUBLIC_METHODS));
+		assertThat(runtimeHints.proxies().jdkProxies()).isEmpty();
+	}
+
+	@Test
+	void shouldRegisterAnnotationAndProxyWithAliasFor() {
+		process(SampleMethodMetaAnnotatedBeanWithAlias.class);
+		RuntimeHints runtimeHints = this.generationContext.getRuntimeHints();
+		assertThat(runtimeHints.reflection().getTypeHint(RetryInvoker.class)).satisfies(typeHint ->
+				assertThat(typeHint.getMemberCategories()).containsOnly(MemberCategory.INVOKE_PUBLIC_METHODS));
+		assertThat(runtimeHints.proxies().jdkProxies()).anySatisfy(jdkProxyHint ->
+				assertThat(jdkProxyHint.getProxiedInterfaces()).containsExactly(
+						TypeReference.of(RetryInvoker.class), TypeReference.of(SynthesizedAnnotation.class)));
+	}
+
+	@Nullable
+	private BeanRegistrationAotContribution createContribution(Class<?> beanClass) {
+		DefaultListableBeanFactory beanFactory = new DefaultListableBeanFactory();
+		beanFactory.registerBeanDefinition(beanClass.getName(), new RootBeanDefinition(beanClass));
+		return this.processor.processAheadOfTime(RegisteredBean.of(beanFactory, beanClass.getName()));
+	}
+
+	private void process(Class<?> beanClass) {
+		BeanRegistrationAotContribution contribution = createContribution(beanClass);
+		assertThat(contribution).isNotNull();
+		contribution.applyTo(this.generationContext, mock(BeanRegistrationCode.class));
+	}
+
+	@Reflective
+	@SuppressWarnings("unused")
+	static class SampleTypeAnnotatedBean {
+
+		private String notManaged;
+
+		public void notManaged() {
+
+		}
+	}
+
+	@SuppressWarnings("unused")
+	static class SampleConstructorAnnotatedBean {
+
+		@Reflective
+		SampleConstructorAnnotatedBean(String name) {
+
+		}
+
+		SampleConstructorAnnotatedBean(Integer nameAsNumber) {
+
+		}
+
+	}
+
+	@SuppressWarnings("unused")
+	static class SampleFieldAnnotatedBean {
+
+		@Reflective
+		String managed;
+
+		String notManaged;
+
+	}
+
+	@SuppressWarnings("unused")
+	static class SampleMethodAnnotatedBean {
+
+		@Reflective
+		void managed() {
+		}
+
+		void notManaged() {
+		}
+
+	}
+
+	@SuppressWarnings("unused")
+	static class SampleMethodMetaAnnotatedBean {
+
+		@SampleInvoker
+		void invoke() {
+		}
+
+		void notManaged() {
+		}
+
+	}
+
+	@SuppressWarnings("unused")
+	static class SampleMethodMetaAnnotatedBeanWithAlias {
+
+		@RetryInvoker
+		void invoke() {
+		}
+
+		void notManaged() {
+		}
+
+	}
+
+	@Target({ ElementType.METHOD, ElementType.ANNOTATION_TYPE })
+	@Retention(RetentionPolicy.RUNTIME)
+	@Documented
+	@Reflective
+	@interface SampleInvoker {
+
+		int retries() default 0;
+
+	}
+
+	@Target({ ElementType.METHOD })
+	@Retention(RetentionPolicy.RUNTIME)
+	@Documented
+	@SampleInvoker
+	@interface RetryInvoker {
+
+		@AliasFor(attribute = "retries", annotation = SampleInvoker.class)
+		int value() default 1;
+
+	}
+
+}