Verify that SynthesizedAnnotation must be public

This commit introduces a test that will fail if SynthesizedAnnotation is
not public as is required by the contract for getProxyClass() in
java.lang.reflect.Proxy.

Issue: SPR-13057

Author: sbrannen

spring-core/src/test/java/org/springframework/core/annotation/AnnotationUtilsTests.java

@@ -34,6 +34,7 @@
 import org.springframework.core.Ordered;
 import org.springframework.core.annotation.subpackage.NonPublicAnnotatedClass;
 import org.springframework.stereotype.Component;
+import org.springframework.util.ClassUtils;
 
 import static org.hamcrest.Matchers.*;
 import static org.junit.Assert.*;
@@ -609,6 +610,32 @@ public void synthesizeAnnotationWithAttributeAliases() throws Exception {
 		assertEquals("actual value attribute: ", "/test", synthesizedWebMapping.value());
 	}
 
+	/**
+	 * Fully reflection-based test that verifies support for
+	 * {@linkplain AnnotationUtils#synthesizeAnnotation synthesizing annotations}
+	 * across packages with non-public visibility of user types (e.g., a non-public
+	 * annotation that uses {@code @AliasFor}).
+	 */
+	@Test
+	@SuppressWarnings("unchecked")
+	public void synthesizeNonPublicAnnotationWithAttributeAliasesFromDifferentPackage() throws Exception {
+
+		Class<?> clazz =
+			ClassUtils.forName("org.springframework.core.annotation.subpackage.NonPublicAliasedAnnotatedClass", null);
+		Class<? extends Annotation> annotationType = (Class<? extends Annotation>)
+			ClassUtils.forName("org.springframework.core.annotation.subpackage.NonPublicAliasedAnnotation", null);
+
+		Annotation annotation = clazz.getAnnotation(annotationType);
+		assertNotNull(annotation);
+		Annotation synthesizedAnnotation = synthesizeAnnotation(annotation);
+		assertNotSame(annotation, synthesizedAnnotation);
+
+		assertNotNull(synthesizedAnnotation);
+		assertEquals("name attribute: ", "test", getValue(synthesizedAnnotation, "name"));
+		assertEquals("aliased path attribute: ", "/test", getValue(synthesizedAnnotation, "path"));
+		assertEquals("aliased path attribute: ", "/test", getValue(synthesizedAnnotation, "value"));
+	}
+
 	@Test
 	public void synthesizeAnnotationWithAttributeAliasesInNestedAnnotations() throws Exception {
 		Hierarchy hierarchy = TestCase.class.getAnnotation(Hierarchy.class);

spring-core/src/test/java/org/springframework/core/annotation/subpackage/NonPublicAliasedAnnotatedClass.java

@@ -0,0 +1,28 @@
+/*
+ * Copyright 2002-2015 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.
+ * 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.core.annotation.subpackage;
+
+/**
+ * Class annotated with a non-public (i.e., package private) custom annotation
+ * that uses {@code @AliasFor}.
+ *
+ * @author Sam Brannen
+ * @since 4.2
+ */
+@NonPublicAliasedAnnotation(name = "test", path = "/test")
+class NonPublicAliasedAnnotatedClass {
+}

spring-core/src/test/java/org/springframework/core/annotation/subpackage/NonPublicAliasedAnnotation.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2002-2015 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.
+ * 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.core.annotation.subpackage;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+import org.springframework.core.annotation.AliasFor;
+
+/**
+ * Non-public mock of {@code org.springframework.web.bind.annotation.RequestMapping}.
+ *
+ * @author Sam Brannen
+ * @since 4.2
+ */
+@Retention(RetentionPolicy.RUNTIME)
+@interface NonPublicAliasedAnnotation {
+
+	String name();
+
+	@AliasFor(attribute = "path")
+	String value() default "";
+
+	@AliasFor(attribute = "value")
+	String path() default "";
+}