Add AnnotationIntrospectionFailureTests

Add a new test class to help cover annotation introspection failure
handling. These tests were previously missing and are important to
ensure that annotation util code changes don't introduce regressions.

See gh-21697

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

@@ -0,0 +1,141 @@
+/*
+ * Copyright 2002-2019 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;
+
+import java.lang.annotation.Annotation;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.reflect.Method;
+
+import org.junit.Test;
+
+import org.springframework.core.OverridingClassLoader;
+import org.springframework.util.ClassUtils;
+import org.springframework.util.ReflectionUtils;
+
+import static org.assertj.core.api.Assertions.*;
+
+/**
+ * Tests that trigger annotation introspection failures and ensure that they are
+ * dealt with correctly.
+ *
+ * @author Phillip Webb
+ * @since 5.2
+ * @see AnnotationUtils
+ * @see AnnotatedElementUtils
+ */
+public class AnnotationIntrospectionFailureTests {
+
+	@Test
+	public void filteredTypeThrowsTypeNotPresentException() throws Exception {
+		FilteringClassLoader classLoader = new FilteringClassLoader(
+				getClass().getClassLoader());
+		Class<?> withExampleAnnotation = ClassUtils.forName(
+				WithExampleAnnotation.class.getName(), classLoader);
+		Annotation annotation = withExampleAnnotation.getAnnotations()[0];
+		Method method = annotation.annotationType().getMethod("value");
+		method.setAccessible(true);
+		assertThatExceptionOfType(TypeNotPresentException.class).isThrownBy(() -> {
+			ReflectionUtils.invokeMethod(method, annotation);
+		}).withCauseInstanceOf(ClassNotFoundException.class);
+	}
+
+	@Test
+	@SuppressWarnings("unchecked")
+	public void filteredTypeInMetaAnnotationWhenUsingAnnotatedElementUtilsHandlesException() throws Exception {
+		FilteringClassLoader classLoader = new FilteringClassLoader(
+				getClass().getClassLoader());
+		Class<?> withExampleMetaAnnotation = ClassUtils.forName(
+				WithExampleMetaAnnotation.class.getName(), classLoader);
+		Class<Annotation> exampleAnnotationClass = (Class<Annotation>) ClassUtils.forName(
+				ExampleAnnotation.class.getName(), classLoader);
+		Class<Annotation> exampleMetaAnnotationClass = (Class<Annotation>) ClassUtils.forName(
+				ExampleMetaAnnotation.class.getName(), classLoader);
+		assertThat(AnnotatedElementUtils.getMergedAnnotationAttributes(
+				withExampleMetaAnnotation, exampleAnnotationClass)).isNull();
+		assertThat(AnnotatedElementUtils.getMergedAnnotationAttributes(
+				withExampleMetaAnnotation,
+				exampleMetaAnnotationClass)).isNull();
+		// Ideally hasAnnotation should return false, however, it currently
+		// detects annotations that might ultimately not load
+		assertThat(AnnotatedElementUtils.hasAnnotation(withExampleMetaAnnotation,
+				exampleAnnotationClass)).isTrue();
+		assertThat(AnnotatedElementUtils.hasAnnotation(withExampleMetaAnnotation,
+				exampleMetaAnnotationClass)).isTrue();
+	}
+
+
+	static class FilteringClassLoader extends OverridingClassLoader {
+
+
+		FilteringClassLoader(ClassLoader parent) {
+			super(parent);
+		}
+
+
+		@Override
+		protected boolean isEligibleForOverriding(String className) {
+			return className.startsWith(
+					AnnotationIntrospectionFailureTests.class.getName());
+		}
+
+		@Override
+		protected Class<?> loadClass(String name, boolean resolve)
+				throws ClassNotFoundException {
+			if (name.startsWith(AnnotationIntrospectionFailureTests.class.getName())
+					&& name.contains("Filtered")) {
+				throw new ClassNotFoundException(name);
+			}
+			return super.loadClass(name, resolve);
+		}
+
+	}
+
+	static class FilteredType {
+
+	}
+
+	@Retention(RetentionPolicy.RUNTIME)
+	static @interface ExampleAnnotation {
+
+		Class<?> value() default Void.class;
+
+	}
+
+	@ExampleAnnotation(FilteredType.class)
+	static class WithExampleAnnotation {
+
+	}
+
+	@Retention(RetentionPolicy.RUNTIME)
+	@ExampleAnnotation
+	static @interface ExampleMetaAnnotation {
+
+		@AliasFor(annotation = ExampleAnnotation.class, attribute = "value")
+		Class<?> example1() default Void.class;
+
+		@AliasFor(annotation = ExampleAnnotation.class, attribute = "value")
+		Class<?> example2() default Void.class;
+
+	}
+
+	@ExampleMetaAnnotation(example1 = FilteredType.class)
+	static class WithExampleMetaAnnotation {
+
+	}
+
+}