Synthesize annotation from map w/ minimal attributes

The initial support for synthesizing an annotation from a Map (or
AnnotationAttributes) introduced in SPR-13067 required that the map
contain key-value pairs for every attribute defined by the supplied
annotationType. However, there are use cases that would benefit from
being able to supply a reduced set of attributes and still have the
annotation synthesized properly.

This commit refines the validation mechanism in
MapAnnotationAttributeExtractor so that a reduced set of attributes may
be supplied. Specifically, if an attribute is missing in the supplied
map the attribute will be set either to value of its alias (if an alias
value configured via @AliasFor exists) or to the value of the
attribute's default value (if defined), and otherwise an exception will
be thrown.

Furthermore, TransactionalTestExecutionListener has been refactored to
take advantage of this new feature by synthesizing an instance of
@TransactionConfiguration solely from the default values of its
declared attributes.

Issue: SPR-13087

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

@@ -24,6 +24,7 @@ import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 import java.lang.reflect.Method;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -55,6 +56,8 @@ import static org.springframework.core.annotation.AnnotationUtils.*;
  */
 public class AnnotationUtilsTests {
 
+	private static final Map<String, Object> EMPTY_ATTRS = Collections.emptyMap();
+
 	@Rule
 	public final ExpectedException exception = ExpectedException.none();
 
@@ -688,25 +691,52 @@ public class AnnotationUtilsTests {
 		assertEquals("value from synthesized component: ", "webController", synthesizedComponent.value());
 	}
 
+	@Test
+	public void synthesizeAnnotationFromMapWithEmptyAttributesWithDefaultsWithoutAttributeAliases() throws Exception {
+		AnnotationWithDefaults annotationWithDefaults = synthesizeAnnotation(EMPTY_ATTRS, AnnotationWithDefaults.class, null);
+		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);
+		assertNotNull(contextConfig);
+		assertEquals("value: ", "", contextConfig.value());
+		assertEquals("locations: ", "", contextConfig.locations());
+	}
+
+	@Test
+	public void synthesizeAnnotationFromMapWithMinimalAttributesWithAttributeAliases() throws Exception {
+		Map<String, Object> map = new HashMap<String, Object>();
+		map.put("locations", "test.xml");
+		ContextConfig contextConfig = synthesizeAnnotation(map, ContextConfig.class, null);
+		assertNotNull(contextConfig);
+		assertEquals("value: ", "test.xml", contextConfig.value());
+		assertEquals("locations: ", "test.xml", contextConfig.locations());
+	}
+
 	@Test
 	public void synthesizeAnnotationFromMapWithMissingAttributeValue() throws Exception {
-		exception.expect(IllegalArgumentException.class);
-		exception.expectMessage(startsWith("Attributes map"));
-		exception.expectMessage(containsString("returned null for required attribute [value]"));
-		exception.expectMessage(containsString("defined by annotation type [" + Component.class.getName() + "]"));
-		synthesizeAnnotation(new HashMap<String, Object>(), Component.class, null);
+		assertMissingTextAttribute(EMPTY_ATTRS);
 	}
 
 	@Test
 	public void synthesizeAnnotationFromMapWithNullAttributeValue() throws Exception {
 		Map<String, Object> map = new HashMap<String, Object>();
-		map.put(VALUE, null);
+		map.put("text", null);
+		assertTrue(map.containsKey("text"));
+		assertMissingTextAttribute(map);
+	}
 
+	private void assertMissingTextAttribute(Map<String, Object> attributes) {
 		exception.expect(IllegalArgumentException.class);
 		exception.expectMessage(startsWith("Attributes map"));
-		exception.expectMessage(containsString("returned null for required attribute [value]"));
-		exception.expectMessage(containsString("defined by annotation type [" + Component.class.getName() + "]"));
-		synthesizeAnnotation(map, Component.class, null);
+		exception.expectMessage(containsString("returned null for required attribute [text]"));
+		exception.expectMessage(containsString("defined by annotation type [" + AnnotationWithoutDefaults.class.getName() + "]"));
+		synthesizeAnnotation(attributes, AnnotationWithoutDefaults.class, null);
 	}
 
 	@Test
@@ -945,14 +975,14 @@ public class AnnotationUtilsTests {
 	}
 
 
-	@Component(value = "meta1")
+	@Component("meta1")
 	@Order
 	@Retention(RetentionPolicy.RUNTIME)
 	@Inherited
 	@interface Meta1 {
 	}
 
-	@Component(value = "meta2")
+	@Component("meta2")
 	@Transactional(readOnly = true)
 	@Retention(RetentionPolicy.RUNTIME)
 	@interface Meta2 {
@@ -1427,4 +1457,16 @@ public class AnnotationUtilsTests {
 	static class ComponentScanClass {
 	}
 
+	@Retention(RetentionPolicy.RUNTIME)
+	@interface AnnotationWithDefaults {
+		String text() default "enigma";
+		boolean predicate() default true;
+		char[] characters() default {'a', 'b', 'c'};
+	}
+
+	@Retention(RetentionPolicy.RUNTIME)
+	@interface AnnotationWithoutDefaults {
+		String text();
+	}
+
 }