Synthesize annotation from defaults

This commit introduces a convenience method in AnnotationUtils for
synthesizing an annotation from its default attribute values.

TransactionalTestExecutionListener has been refactored to invoke this
new convenience method.

Issue: SPR-13087

Author: sbrannen

spring-core/src/main/java/org/springframework/core/annotation/AnnotationUtils.java

@@ -1207,6 +1207,7 @@ static <A extends Annotation> A synthesizeAnnotation(A annotation) {
 	 * {@code @AliasFor} is detected
 	 * @since 4.2
 	 * @see #synthesizeAnnotation(Map, Class, AnnotatedElement)
+	 * @see #synthesizeAnnotation(Class)
 	 */
 	@SuppressWarnings("unchecked")
 	public static <A extends Annotation> A synthesizeAnnotation(A annotation, AnnotatedElement annotatedElement) {
@@ -1256,6 +1257,7 @@ public static <A extends Annotation> A synthesizeAnnotation(A annotation, Annota
 	 * {@code @AliasFor} is detected
 	 * @since 4.2
 	 * @see #synthesizeAnnotation(Annotation, AnnotatedElement)
+	 * @see #synthesizeAnnotation(Class)
 	 */
 	@SuppressWarnings("unchecked")
 	public static <A extends Annotation> A synthesizeAnnotation(Map<String, Object> attributes,
@@ -1275,6 +1277,26 @@ public static <A extends Annotation> A synthesizeAnnotation(Map<String, Object>
 		return synthesizedAnnotation;
 	}
 
+	/**
+	 * <em>Synthesize</em> an annotation from its default attributes values.
+	 * <p>This method simply delegates to
+	 * {@link #synthesizeAnnotation(Map, Class, AnnotatedElement)},
+	 * supplying an empty map for the source attribute values and {@code null}
+	 * for the {@link AnnotatedElement}.
+	 *
+	 * @param annotationType the type of annotation to synthesize; never {@code null}
+	 * @return the synthesized annotation
+	 * @throws IllegalArgumentException if a required attribute is missing
+	 * @throws AnnotationConfigurationException if invalid configuration of
+	 * {@code @AliasFor} is detected
+	 * @since 4.2
+	 * @see #synthesizeAnnotation(Map, Class, AnnotatedElement)
+	 * @see #synthesizeAnnotation(Annotation, AnnotatedElement)
+	 */
+	public static <A extends Annotation> A synthesizeAnnotation(Class<A> annotationType) {
+		return synthesizeAnnotation(Collections.<String, Object> emptyMap(), annotationType, null);
+	}
+
 	/**
 	 * <em>Synthesize</em> the supplied array of {@code annotations} by
 	 * creating a new array of the same size and type and populating it

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

@@ -56,8 +56,6 @@
  */
 public class AnnotationUtilsTests {
 
-	private static final Map<String, Object> EMPTY_ATTRS = Collections.emptyMap();
-
 	@Rule
 	public final ExpectedException exception = ExpectedException.none();
 
@@ -840,17 +838,17 @@ public void synthesizeAnnotationFromMapWithoutAttributeAliases() throws Exceptio
 	}
 
 	@Test
-	public void synthesizeAnnotationFromMapWithEmptyAttributesWithDefaultsWithoutAttributeAliases() throws Exception {
-		AnnotationWithDefaults annotationWithDefaults = synthesizeAnnotation(EMPTY_ATTRS, AnnotationWithDefaults.class, null);
+	public void synthesizeAnnotationFromDefaultsWithoutAttributeAliases() throws Exception {
+		AnnotationWithDefaults annotationWithDefaults = synthesizeAnnotation(AnnotationWithDefaults.class);
 		assertNotNull(annotationWithDefaults);
 		assertEquals("text: ", "enigma", annotationWithDefaults.text());
 		assertTrue("predicate: ", annotationWithDefaults.predicate());
 		assertArrayEquals("characters: ", new char[] { 'a', 'b', 'c' }, annotationWithDefaults.characters());
 	}
 
 	@Test
-	public void synthesizeAnnotationFromMapWithEmptyAttributesWithDefaultsWithAttributeAliases() throws Exception {
-		ContextConfig contextConfig = synthesizeAnnotation(EMPTY_ATTRS, ContextConfig.class, null);
+	public void synthesizeAnnotationFromDefaultsWithAttributeAliases() throws Exception {
+		ContextConfig contextConfig = synthesizeAnnotation(ContextConfig.class);
 		assertNotNull(contextConfig);
 		assertEquals("value: ", "", contextConfig.value());
 		assertEquals("locations: ", "", contextConfig.locations());
@@ -868,7 +866,7 @@ public void synthesizeAnnotationFromMapWithMinimalAttributesWithAttributeAliases
 
 	@Test
 	public void synthesizeAnnotationFromMapWithMissingAttributeValue() throws Exception {
-		assertMissingTextAttribute(EMPTY_ATTRS);
+		assertMissingTextAttribute(Collections.emptyMap());
 	}
 
 	@Test

spring-test/src/main/java/org/springframework/test/context/transaction/TransactionalTestExecutionListener.java

@@ -135,7 +135,7 @@ public class TransactionalTestExecutionListener extends AbstractTestExecutionLis
 	private static final Log logger = LogFactory.getLog(TransactionalTestExecutionListener.class);
 
 	private static final TransactionConfiguration defaultTransactionConfiguration =
-			AnnotationUtils.synthesizeAnnotation(Collections.<String, Object> emptyMap(), TransactionConfiguration.class, null);
+			AnnotationUtils.synthesizeAnnotation(TransactionConfiguration.class);
 
 	protected final TransactionAttributeSource attributeSource = new AnnotationTransactionAttributeSource();