/*
* Copyright 2002-2008 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.reflect.Method;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
import org.springframework.core.BridgeMethodResolver;
import org.springframework.util.Assert;
/**
* General utility methods for working with annotations, handling bridge methods
* (which the compiler generates for generic declarations) as well as super
* methods (for optional "annotation inheritance"). Note that none of
* this is provided by the JDK's introspection facilities themselves.
*
* <p>As a general rule for runtime-retained annotations (e.g. for transaction
* control, authorization or service exposure), always use the lookup methods on
* this class (e.g., {@link #findAnnotation(Method, Class)},
* {@link #getAnnotation(Method, Class)}, and {@link #getAnnotations(Method)})
* instead of the plain annotation lookup methods in the JDK. You can still
* explicitly choose between lookup on the given class level only
* ({@link #getAnnotation(Method, Class)}) and lookup in the entire inheritance
* hierarchy of the given method ({@link #findAnnotation(Method, Class)}).
*
* @author Rob Harrop
* @author Juergen Hoeller
* @author Sam Brannen
* @author Mark Fisher
* @since 2.0
* @see java.lang.reflect.Method#getAnnotations()
* @see java.lang.reflect.Method#getAnnotation(Class)
*/
public abstract class AnnotationUtils {
/** The attribute name for annotations with a single element */
static final String VALUE = "value";
/**
* Get all {@link Annotation Annotations} from the supplied {@link Method}.
* <p>Correctly handles bridge {@link Method Methods} generated by the compiler.
* @param method the method to look for annotations on
* @return the annotations found
* @see org.springframework.core.BridgeMethodResolver#findBridgedMethod(Method)
*/
public static Annotation[] getAnnotations(Method method) {
return BridgeMethodResolver.findBridgedMethod(method).getAnnotations();
}
/**
* Get a single {@link Annotation} of <code>annotationType</code> from the
* supplied {@link Method}.
* <p>Correctly handles bridge {@link Method Methods} generated by the compiler.
* @param method the method to look for annotations on
* @param annotationType the annotation class to look for
* @return the annotations found
* @see org.springframework.core.BridgeMethodResolver#findBridgedMethod(Method)
*/
public static <A extends Annotation> A getAnnotation(Method method, Class<A> annotationType) {
return BridgeMethodResolver.findBridgedMethod(method).getAnnotation(annotationType);
}
/**
* Get a single {@link Annotation} of <code>annotationType</code> from the
* supplied {@link Method}, traversing its super methods if no annotation
* can be found on the given method itself.
* <p>Annotations on methods are not inherited by default, so we need to handle
* this explicitly. Tge
* @param method the method to look for annotations on
* @param annotationType the annotation class to look for
* @return the annotation found, or <code>null</code> if none found
*/
public static <A extends Annotation> A findAnnotation(Method method, Class<A> annotationType) {
A annotation = getAnnotation(method, annotationType);
Class<?> cl = method.getDeclaringClass();
while (annotation == null) {
cl = cl.getSuperclass();
if (cl == null || cl == Object.class) {
break;
}
try {
Method equivalentMethod = cl.getDeclaredMethod(method.getName(), method.getParameterTypes());
annotation = getAnnotation(equivalentMethod, annotationType);
}
catch (NoSuchMethodException ex) {
// We're done...
}
}
return annotation;
}
/**
* Find a single {@link Annotation} of <code>annotationType</code> from the
* supplied {@link Class}, traversing its interfaces and super classes
* if no annotation can be found on the given class itself.
* <p>This method explicitly handles class-level annotations which are
* not declared as {@link java.lang.annotation.Inherited inherited}
* <i>as well as annotations on interfaces</i>.
* <p>The algorithm operates as follows: Searches for an annotation on the given
* class and returns it if found. Else searches all interfaces that the given
* class declares, returning the annotation from the first matching candidate,
* if any. Else proceeds with introspection of the superclass of the given class,
* checking the superclass itself; if no annotation found there, proceeds with
* the interfaces that the superclass declares. Recursing up through the entire
* superclass hierarchy if no match is found.
* @param clazz the class to look for annotations on
* @param annotationType the annotation class to look for
* @return the annotation found, or <code>null</code> if none found
*/
public static <A extends Annotation> A findAnnotation(Class<?> clazz, Class<A> annotationType) {
Assert.notNull(clazz, "Class must not be null");
A annotation = clazz.getAnnotation(annotationType);
if (annotation != null) {
return annotation;
}
for (Class<?> ifc : clazz.getInterfaces()) {
annotation = findAnnotation(ifc, annotationType);
if (annotation != null) {
return annotation;
}
}
Class superClass = clazz.getSuperclass();
if (superClass == null || superClass == Object.class) {
return null;
}
return findAnnotation(superClass, annotationType);
}
/**
* Find the first {@link Class} in the inheritance hierarchy of the
* specified <code>clazz</code> (including the specified
* <code>clazz</code> itself) which declares an annotation for the
* specified <code>annotationType</code>, or <code>null</code> if not
* found. If the supplied <code>clazz</code> is <code>null</code>,
* <code>null</code> will be returned.
* <p>If the supplied <code>clazz</code> is an interface, only the interface
* itself will be checked; the inheritance hierarchy for interfaces will not
* be traversed.
* <p>The standard {@link Class} API does not provide a mechanism for
* determining which class in an inheritance hierarchy actually declares an
* {@link Annotation}, so we need to handle this explicitly.
* @param annotationType the Class object corresponding to the annotation type
* @param clazz the Class object corresponding to the class on which to
* check for the annotation, or <code>null</code>.
* @return the first {@link Class} in the inheritance hierarchy of the
* specified <code>clazz</code> which declares an annotation for the specified
* <code>annotationType</code>, or <code>null</code> if not found.
* @see Class#isAnnotationPresent(Class)
* @see Class#getDeclaredAnnotations()
*/
public static Class<?> findAnnotationDeclaringClass(Class<? extends Annotation> annotationType, Class<?> clazz) {
Assert.notNull(annotationType, "Annotation type must not be null");
if (clazz == null || clazz.equals(Object.class)) {
return null;
}
return (isAnnotationDeclaredLocally(annotationType, clazz)) ?
clazz : findAnnotationDeclaringClass(annotationType, clazz.getSuperclass());
}
/**
* Determine whether an annotation for the specified <code>annotationType</code>
* is declared locally on the supplied <code>clazz</code>.
* The supplied {@link Class} object may represent any type.
* <p>Note: This method does <strong>not</strong> determine if the annotation
* is {@link java.lang.annotation.Inherited inherited}. For greater clarity
* regarding inherited annotations, consider using
* {@link #isAnnotationInherited(Class, Class)} instead.
* @param annotationType the Class object corresponding to the annotation type
* @param clazz the Class object corresponding to the class on which to
* check for the annotation
* @return <code>true</code> if an annotation for the specified
* <code>annotationType</code> is declared locally on the supplied <code>clazz</code>
* @see Class#getDeclaredAnnotations()
* @see #isAnnotationInherited(Class, Class)
*/
public static boolean isAnnotationDeclaredLocally(Class<? extends Annotation> annotationType, Class<?> clazz) {
Assert.notNull(annotationType, "Annotation type must not be null");
Assert.notNull(clazz, "Class must not be null");
boolean declaredLocally = false;
for (Annotation annotation : Arrays.asList(clazz.getDeclaredAnnotations())) {
if (annotation.annotationType().equals(annotationType)) {
declaredLocally = true;
break;
}
}
return declaredLocally;
}
/**
* Determine whether an annotation for the specified <code>annotationType</code>
* is present on the supplied <code>clazz</code> and is
* {@link java.lang.annotation.Inherited inherited}
* (i.e., not declared locally for the class).
* <p>If the supplied <code>clazz</code> is an interface, only the interface
* itself will be checked. In accord with standard meta-annotation
* semantics, the inheritance hierarchy for interfaces will not be
* traversed. See the {@link java.lang.annotation.Inherited JavaDoc} for the
* @Inherited meta-annotation for further details regarding annotation
* inheritance.
* @param annotationType the Class object corresponding to the annotation type
* @param clazz the Class object corresponding to the class on which to
* check for the annotation
* @return <code>true</code> if an annotation for the specified
* <code>annotationType</code> is present on the supplied <code>clazz</code>
* and is {@link java.lang.annotation.Inherited inherited}
* @see Class#isAnnotationPresent(Class)
* @see #isAnnotationDeclaredLocally(Class, Class)
*/
public static boolean isAnnotationInherited(Class<? extends Annotation> annotationType, Class<?> clazz) {
Assert.notNull(annotationType, "Annotation type must not be null");
Assert.notNull(clazz, "Class must not be null");
return (clazz.isAnnotationPresent(annotationType) && !isAnnotationDeclaredLocally(annotationType, clazz));
}
/**
* Retrieve the given annotation's attributes as a Map.
* @param annotation the annotation to retrieve the attributes for
* @return the Map of annotation attributes, with attribute names as keys
* and corresponding attribute values as values
*/
public static Map<String, Object> getAnnotationAttributes(Annotation annotation) {
Map<String, Object> attrs = new HashMap<String, Object>();
Method[] methods = annotation.annotationType().getDeclaredMethods();
for (int j = 0; j < methods.length; j++) {
Method method = methods[j];
if (method.getParameterTypes().length == 0 && method.getReturnType() != void.class) {
try {
attrs.put(method.getName(), method.invoke(annotation));
}
catch (Exception ex) {
throw new IllegalStateException("Could not obtain annotation attribute values", ex);
}
}
}
return attrs;
}
/**
* Retrieve the <em>value</em> of the <code>"value"</code>
* attribute of a single-element Annotation, given an annotation instance.
* @param annotation the annotation instance from which to retrieve the value
* @return the attribute value, or <code>null</code> if not found
* @see #getValue(Annotation, String)
*/
public static Object getValue(Annotation annotation) {
return getValue(annotation, VALUE);
}
/**
* Retrieve the <em>value</em> of a named Annotation attribute, given an
* annotation instance.
* @see #getValue(Annotation)
* @param annotation the annotation instance from which to retrieve the value
* @param attributeName the name of the attribute value to retrieve
* @return the attribute value, or <code>null</code> if not found
*/
public static Object getValue(Annotation annotation, String attributeName) {
try {
Method method = annotation.annotationType().getDeclaredMethod(attributeName, new Class[0]);
return method.invoke(annotation);
}
catch (Exception ex) {
return null;
}
}
/**
* Retrieve the <em>default value</em> of the
* <code>"value"</code> attribute of a single-element
* Annotation, given an annotation instance.
* @param annotation the annotation instance from which to retrieve
* the default value
* @return the default value, or <code>null</code> if not found
* @see #getDefaultValue(Annotation, String)
*/
public static Object getDefaultValue(Annotation annotation) {
return getDefaultValue(annotation, VALUE);
}
/**
* Retrieve the <em>default value</em> of a named Annotation attribute,
* given an annotation instance.
* @param annotation the annotation instance from which to retrieve
* the default value
* @param attributeName the name of the attribute value to retrieve
* @return the default value of the named attribute, or <code>null</code>
* if not found.
* @see #getDefaultValue(Class, String)
*/
public static Object getDefaultValue(Annotation annotation, String attributeName) {
return getDefaultValue(annotation.annotationType(), attributeName);
}
/**
* Retrieve the <em>default value</em> of the
* <code>"value"</code> attribute of a single-element
* Annotation, given the {@link Class annotation type}.
* @param annotationType the <em>annotation type</em> for which the
* default value should be retrieved
* @return the default value, or <code>null</code> if not found
* @see #getDefaultValue(Class, String)
*/
public static Object getDefaultValue(Class<? extends Annotation> annotationType) {
return getDefaultValue(annotationType, VALUE);
}
/**
* Retrieve the <em>default value</em> of a named Annotation attribute,
* given the {@link Class annotation type}.
* @param annotationType the <em>annotation type</em> for which the
* default value should be retrieved
* @param attributeName the name of the attribute value to retrieve.
* @return the default value of the named attribute, or <code>null</code>
* if not found
* @see #getDefaultValue(Annotation, String)
*/
public static Object getDefaultValue(Class<? extends Annotation> annotationType, String attributeName) {
try {
Method method = annotationType.getDeclaredMethod(attributeName, new Class[0]);
return method.getDefaultValue();
}
catch (Exception ex) {
return null;
}
}
}