Introduce getAliasedClassArray() in AnnotationAttributes

Issue: SPR-11393

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

@@ -114,7 +114,7 @@ public class AnnotationAttributes extends LinkedHashMap<String, Object> {
 	 * if it is not of the expected type
 	 */
 	public String getString(String attributeName) {
-		return doGet(attributeName, String.class);
+		return getRequiredAttribute(attributeName, String.class);
 	}
 
 	/**
@@ -130,7 +130,7 @@ public class AnnotationAttributes extends LinkedHashMap<String, Object> {
 	 * if it is not of the expected type
 	 */
 	public String[] getStringArray(String attributeName) {
-		return doGet(attributeName, String[].class);
+		return getRequiredAttribute(attributeName, String[].class);
 	}
 
 	/**
@@ -157,32 +157,7 @@ public class AnnotationAttributes extends LinkedHashMap<String, Object> {
 	 */
 	public String[] getAliasedStringArray(String attributeName, Class<? extends Annotation> annotationType,
 			Object annotationSource) {
-
-		Assert.hasText(attributeName, "attributeName must not be null or empty");
-		Assert.notNull(annotationType, "annotationType must not be null");
-
-		String[] attributeValue = getStringArrayWithoutNullCheck(attributeName);
-		String aliasName = AnnotationUtils.getAttributeAliasMap(annotationType).get(attributeName);
-		String[] aliasValue = getStringArrayWithoutNullCheck(aliasName);
-		boolean attributeDeclared = !ObjectUtils.isEmpty(attributeValue);
-		boolean aliasDeclared = !ObjectUtils.isEmpty(aliasValue);
-
-		if (!ObjectUtils.nullSafeEquals(attributeValue, aliasValue) && attributeDeclared && aliasDeclared) {
-			String elementName = (annotationSource == null ? "unknown element" : annotationSource.toString());
-			String msg = String.format("In annotation [%s] declared on [%s], "
-					+ "attribute [%s] and its alias [%s] are present with values of [%s] and [%s], "
-					+ "but only one is permitted.", this.displayName, elementName, attributeName, aliasName,
-				ObjectUtils.nullSafeToString(attributeValue), ObjectUtils.nullSafeToString(aliasValue));
-			throw new AnnotationConfigurationException(msg);
-		}
-
-		if (!attributeDeclared) {
-			attributeValue = aliasValue;
-		}
-
-		assertAttributePresence(attributeName, aliasName, attributeValue);
-
-		return attributeValue;
+		return getRequiredArrayWithAttributeAlias(attributeName, annotationType, annotationSource, String[].class);
 	}
 
 	/**
@@ -195,7 +170,7 @@ public class AnnotationAttributes extends LinkedHashMap<String, Object> {
 	 * if it is not of the expected type
 	 */
 	public boolean getBoolean(String attributeName) {
-		return doGet(attributeName, Boolean.class);
+		return getRequiredAttribute(attributeName, Boolean.class);
 	}
 
 	/**
@@ -209,7 +184,7 @@ public class AnnotationAttributes extends LinkedHashMap<String, Object> {
 	 */
 	@SuppressWarnings("unchecked")
 	public <N extends Number> N getNumber(String attributeName) {
-		return (N) doGet(attributeName, Number.class);
+		return (N) getRequiredAttribute(attributeName, Number.class);
 	}
 
 	/**
@@ -223,7 +198,7 @@ public class AnnotationAttributes extends LinkedHashMap<String, Object> {
 	 */
 	@SuppressWarnings("unchecked")
 	public <E extends Enum<?>> E getEnum(String attributeName) {
-		return (E) doGet(attributeName, Enum.class);
+		return (E) getRequiredAttribute(attributeName, Enum.class);
 	}
 
 	/**
@@ -237,7 +212,7 @@ public class AnnotationAttributes extends LinkedHashMap<String, Object> {
 	 */
 	@SuppressWarnings("unchecked")
 	public <T> Class<? extends T> getClass(String attributeName) {
-		return doGet(attributeName, Class.class);
+		return getRequiredAttribute(attributeName, Class.class);
 	}
 
 	/**
@@ -253,7 +228,34 @@ public class AnnotationAttributes extends LinkedHashMap<String, Object> {
 	 * if it is not of the expected type
 	 */
 	public Class<?>[] getClassArray(String attributeName) {
-		return doGet(attributeName, Class[].class);
+		return getRequiredAttribute(attributeName, Class[].class);
+	}
+
+	/**
+	 * Get the value stored under the specified {@code attributeName} as an
+	 * array of classes, taking into account alias semantics defined via
+	 * {@link AliasFor @AliasFor}.
+	 * <p>If there is no value stored under the specified {@code attributeName}
+	 * but the attribute has an alias declared via {@code @AliasFor}, the
+	 * value of the alias will be returned.
+	 *
+	 * @param attributeName the name of the attribute to get; never
+	 * {@code null} or empty
+	 * @param annotationType the type of annotation represented by this
+	 * {@code AnnotationAttributes} instance; never {@code null}
+	 * @param annotationSource the source of the annotation represented by
+	 * this {@code AnnotationAttributes} (e.g., the {@link AnnotatedElement});
+	 * or {@code null} if unknown
+	 * @return the array of classes
+	 * @throws IllegalArgumentException if the attribute and its alias do
+	 * not exist or are not of type {@code Class[]}
+	 * @throws AnnotationConfigurationException if the attribute and its
+	 * alias are both present with different non-empty values
+	 * @since 4.2
+	 */
+	public Class<?>[] getAliasedClassArray(String attributeName, Class<? extends Annotation> annotationType,
+			Object annotationSource) {
+		return getRequiredArrayWithAttributeAlias(attributeName, annotationType, annotationSource, Class[].class);
 	}
 
 	/**
@@ -268,7 +270,7 @@ public class AnnotationAttributes extends LinkedHashMap<String, Object> {
 	 * if it is not of the expected type
 	 */
 	public AnnotationAttributes getAnnotation(String attributeName) {
-		return doGet(attributeName, AnnotationAttributes.class);
+		return getRequiredAttribute(attributeName, AnnotationAttributes.class);
 	}
 
 	/**
@@ -283,7 +285,7 @@ public class AnnotationAttributes extends LinkedHashMap<String, Object> {
 	 * @since 4.2
 	 */
 	public <A extends Annotation> A getAnnotation(String attributeName, Class<A> annotationType) {
-		return doGet(attributeName, annotationType);
+		return getRequiredAttribute(attributeName, annotationType);
 	}
 
 	/**
@@ -301,7 +303,7 @@ public class AnnotationAttributes extends LinkedHashMap<String, Object> {
 	 * if it is not of the expected type
 	 */
 	public AnnotationAttributes[] getAnnotationArray(String attributeName) {
-		return doGet(attributeName, AnnotationAttributes[].class);
+		return getRequiredAttribute(attributeName, AnnotationAttributes[].class);
 	}
 
 	/**
@@ -321,7 +323,83 @@ public class AnnotationAttributes extends LinkedHashMap<String, Object> {
 	@SuppressWarnings("unchecked")
 	public <A extends Annotation> A[] getAnnotationArray(String attributeName, Class<A> annotationType) {
 		Object array = Array.newInstance(annotationType, 0);
-		return (A[]) doGet(attributeName, array.getClass());
+		return (A[]) getRequiredAttribute(attributeName, array.getClass());
+	}
+
+	/**
+	 * Get the value stored under the specified {@code attributeName} as an
+	 * array of the {@code expectedType}, taking into account alias semantics
+	 * defined via {@link AliasFor @AliasFor}.
+	 * <p>If there is no value stored under the specified {@code attributeName}
+	 * but the attribute has an alias declared via {@code @AliasFor}, the
+	 * value of the alias will be returned.
+	 *
+	 * @param attributeName the name of the attribute to get; never
+	 * {@code null} or empty
+	 * @param annotationType the type of annotation represented by this
+	 * {@code AnnotationAttributes} instance; never {@code null}
+	 * @param annotationSource the source of the annotation represented by
+	 * this {@code AnnotationAttributes} (e.g., the {@link AnnotatedElement});
+	 * or {@code null} if unknown
+	 * @param expectedType the expected array type; never {@code null}
+	 * @return the array of values
+	 * @throws IllegalArgumentException if the attribute and its alias do
+	 * not exist or are not of the {@code expectedType}, or if the
+	 * {@code expectedType} is not an array
+	 * @throws AnnotationConfigurationException if the attribute and its
+	 * alias are both present with different non-empty values
+	 * @since 4.2
+	 */
+	private <T> T getRequiredArrayWithAttributeAlias(String attributeName, Class<? extends Annotation> annotationType,
+			Object annotationSource, Class<T> expectedType) {
+
+		Assert.hasText(attributeName, "attributeName must not be null or empty");
+		Assert.notNull(annotationType, "annotationType must not be null");
+		Assert.notNull(expectedType, "expectedType must not be null");
+		Assert.isTrue(expectedType.isArray(), "expectedType must be an array");
+
+		T attributeValue = getAttribute(attributeName, expectedType);
+		String aliasName = AnnotationUtils.getAttributeAliasMap(annotationType).get(attributeName);
+		T aliasValue = getAttribute(aliasName, expectedType);
+		boolean attributeDeclared = !ObjectUtils.isEmpty((Object[]) attributeValue);
+		boolean aliasDeclared = !ObjectUtils.isEmpty((Object[]) aliasValue);
+
+		if (!ObjectUtils.nullSafeEquals(attributeValue, aliasValue) && attributeDeclared && aliasDeclared) {
+			String elementName = (annotationSource == null ? "unknown element" : annotationSource.toString());
+			String msg = String.format("In annotation [%s] declared on [%s], "
+					+ "attribute [%s] and its alias [%s] are present with values of [%s] and [%s], "
+					+ "but only one is permitted.", this.displayName, elementName, attributeName, aliasName,
+				ObjectUtils.nullSafeToString(attributeValue), ObjectUtils.nullSafeToString(aliasValue));
+			throw new AnnotationConfigurationException(msg);
+		}
+
+		if (!attributeDeclared) {
+			attributeValue = aliasValue;
+		}
+
+		assertAttributePresence(attributeName, aliasName, attributeValue);
+
+		return attributeValue;
+	}
+
+	/**
+	 * Get the value stored under the specified {@code attributeName},
+	 * ensuring that the value is of the {@code expectedType}.
+	 * @param attributeName the name of the attribute to get; never
+	 * {@code null} or empty
+	 * @param expectedType the expected type; never {@code null}
+	 * @return the value
+	 * @throws IllegalArgumentException if the attribute is not of the
+	 * expected type
+	 * @see #getRequiredAttribute(String, Class)
+	 */
+	@SuppressWarnings("unchecked")
+	private <T> T getAttribute(String attributeName, Class<T> expectedType) {
+		Object value = get(attributeName);
+		if (value != null) {
+			assertAttributeType(attributeName, value, expectedType);
+		}
+		return (T) value;
 	}
 
 	/**
@@ -340,7 +418,7 @@ public class AnnotationAttributes extends LinkedHashMap<String, Object> {
 	 * if it is not of the expected type
 	 */
 	@SuppressWarnings("unchecked")
-	private <T> T doGet(String attributeName, Class<T> expectedType) {
+	private <T> T getRequiredAttribute(String attributeName, Class<T> expectedType) {
 		Assert.hasText(attributeName, "attributeName must not be null or empty");
 		Object value = get(attributeName);
 		assertAttributePresence(attributeName, value);
@@ -378,14 +456,6 @@ public class AnnotationAttributes extends LinkedHashMap<String, Object> {
 		}
 	}
 
-	private String[] getStringArrayWithoutNullCheck(String attributeName) {
-		Object value = get(attributeName);
-		if (value != null) {
-			assertAttributeType(attributeName, value, String[].class);
-		}
-		return (String[]) value;
-	}
-
 	/**
 	 * Store the supplied {@code value} in this map under the specified
 	 * {@code key}, unless a value is already stored under the key.

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

@@ -209,6 +209,71 @@ public class AnnotationAttributesTests {
 		return attributes.getAliasedStringArray(attributeName, ContextConfig.class, null);
 	}
 
+	@Test
+	public void getAliasedClassArray() {
+		final Class<?>[] INPUT = new Class<?>[] { String.class };
+		final Class<?>[] EMPTY = new Class<?>[0];
+
+		attributes.clear();
+		attributes.put("classes", INPUT);
+		assertArrayEquals(INPUT, getAliasedClassArray("classes"));
+		assertArrayEquals(INPUT, getAliasedClassArray("value"));
+
+		attributes.clear();
+		attributes.put("value", INPUT);
+		assertArrayEquals(INPUT, getAliasedClassArray("classes"));
+		assertArrayEquals(INPUT, getAliasedClassArray("value"));
+
+		attributes.clear();
+		attributes.put("classes", INPUT);
+		attributes.put("value", INPUT);
+		assertArrayEquals(INPUT, getAliasedClassArray("classes"));
+		assertArrayEquals(INPUT, getAliasedClassArray("value"));
+
+		attributes.clear();
+		attributes.put("classes", INPUT);
+		attributes.put("value", EMPTY);
+		assertArrayEquals(INPUT, getAliasedClassArray("classes"));
+		assertArrayEquals(INPUT, getAliasedClassArray("value"));
+
+		attributes.clear();
+		attributes.put("classes", EMPTY);
+		attributes.put("value", INPUT);
+		assertArrayEquals(INPUT, getAliasedClassArray("classes"));
+		assertArrayEquals(INPUT, getAliasedClassArray("value"));
+
+		attributes.clear();
+		attributes.put("classes", EMPTY);
+		attributes.put("value", EMPTY);
+		assertArrayEquals(EMPTY, getAliasedClassArray("classes"));
+		assertArrayEquals(EMPTY, getAliasedClassArray("value"));
+	}
+
+	@Test
+	public void getAliasedClassArrayWithMissingAliasedAttributes() {
+		exception.expect(IllegalArgumentException.class);
+		exception.expectMessage(equalTo("Neither attribute 'classes' nor its alias 'value' was found in attributes for annotation [unknown]"));
+		getAliasedClassArray("classes");
+	}
+
+	@Test
+	public void getAliasedClassArrayWithDifferentAliasedValues() {
+		attributes.put("classes", new Class[] { String.class });
+		attributes.put("value", new Class[] { Number.class });
+
+		exception.expect(AnnotationConfigurationException.class);
+		exception.expectMessage(containsString("In annotation [unknown]"));
+		exception.expectMessage(containsString("attribute [classes] and its alias [value]"));
+		exception.expectMessage(containsString("[{class java.lang.String}] and [{class java.lang.Number}]"));
+		exception.expectMessage(containsString("but only one is permitted"));
+
+		getAliasedClassArray("classes");
+	}
+
+	private Class<?>[] getAliasedClassArray(String attributeName) {
+		return attributes.getAliasedClassArray(attributeName, Filter.class, null);
+	}
+
 
 	enum Color {
 		RED, WHITE, BLUE
@@ -216,6 +281,13 @@ public class AnnotationAttributesTests {
 
 	@Retention(RetentionPolicy.RUNTIME)
 	@interface Filter {
+
+		@AliasFor(attribute = "classes")
+		Class<?>[] value() default {};
+
+		@AliasFor(attribute = "value")
+		Class<?>[] classes() default {};
+
 		String pattern();
 	}