org.springframework.core.annotation.AnnotationUtils Maven / Gradle / Ivy
/*
* Copyright 2002-2010 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 java.util.WeakHashMap;
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.
*
* 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";
private static final Map annotatedInterfaceCache = new WeakHashMap();
/**
* Get all {@link Annotation Annotations} from the supplied {@link Method}.
* 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 annotationType from the supplied {@link Method}.
*
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 getAnnotation(Method method, Class annotationType) {
Method resolvedMethod = BridgeMethodResolver.findBridgedMethod(method);
A ann = resolvedMethod.getAnnotation(annotationType);
if (ann == null) {
for (Annotation metaAnn : resolvedMethod.getAnnotations()) {
ann = metaAnn.annotationType().getAnnotation(annotationType);
if (ann != null) {
break;
}
}
}
return ann;
}
/**
* Get a single {@link Annotation} of annotationType from the supplied {@link Method},
* traversing its super methods if no annotation can be found on the given method itself.
* Annotations on methods are not inherited by default, so we need to handle this explicitly.
* @param method the method to look for annotations on
* @param annotationType the annotation class to look for
* @return the annotation found, or null if none found
*/
public static A findAnnotation(Method method, Class annotationType) {
A annotation = getAnnotation(method, annotationType);
Class cl = method.getDeclaringClass();
if (annotation == null) {
annotation = searchOnInterfaces(method, annotationType, cl.getInterfaces());
}
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);
if (annotation == null) {
annotation = searchOnInterfaces(method, annotationType, cl.getInterfaces());
}
}
catch (NoSuchMethodException ex) {
// We're done...
}
}
return annotation;
}
private static A searchOnInterfaces(Method method, Class annotationType, Class[] ifcs) {
A annotation = null;
for (Class iface : ifcs) {
if (isInterfaceWithAnnotatedMethods(iface)) {
try {
Method equivalentMethod = iface.getMethod(method.getName(), method.getParameterTypes());
annotation = getAnnotation(equivalentMethod, annotationType);
}
catch (NoSuchMethodException ex) {
// Skip this interface - it doesn't have the method...
}
if (annotation != null) {
break;
}
}
}
return annotation;
}
private static boolean isInterfaceWithAnnotatedMethods(Class iface) {
synchronized (annotatedInterfaceCache) {
Boolean flag = annotatedInterfaceCache.get(iface);
if (flag != null) {
return flag;
}
boolean found = false;
for (Method ifcMethod : iface.getMethods()) {
if (ifcMethod.getAnnotations().length > 0) {
found = true;
break;
}
}
annotatedInterfaceCache.put(iface, found);
return found;
}
}
/**
* Find a single {@link Annotation} of annotationType from the supplied {@link Class},
* traversing its interfaces and superclasses if no annotation can be found on the given class itself.
* This method explicitly handles class-level annotations which are not declared as
* {@link java.lang.annotation.Inherited inherited} as well as annotations on interfaces.
*
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 null if none found
*/
public static A findAnnotation(Class clazz, Class 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;
}
}
if (!Annotation.class.isAssignableFrom(clazz)) {
for (Annotation ann : clazz.getAnnotations()) {
annotation = findAnnotation(ann.annotationType(), 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 clazz
* (including the specified clazz itself) which declares an annotation for the
* specified annotationType, or null if not found. If the supplied
* clazz is null, null will be returned.
* If the supplied clazz is an interface, only the interface itself will be checked;
* the inheritance hierarchy for interfaces will not be traversed.
*
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 null
* @return the first {@link Class} in the inheritance hierarchy of the specified clazz
* which declares an annotation for the specified annotationType, or null
* if not found
* @see Class#isAnnotationPresent(Class)
* @see Class#getDeclaredAnnotations()
*/
public static Class findAnnotationDeclaringClass(Class 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 annotationType is
* declared locally on the supplied clazz. The supplied {@link Class}
* may represent any type.
*
Note: This method does not 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 true if an annotation for the specified annotationType
* is declared locally on the supplied clazz
* @see Class#getDeclaredAnnotations()
* @see #isAnnotationInherited(Class, Class)
*/
public static boolean isAnnotationDeclaredLocally(Class 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 annotationType is present
* on the supplied clazz and is {@link java.lang.annotation.Inherited inherited}
* i.e., not declared locally for the class).
*
If the supplied clazz is an interface, only the interface itself will be checked.
* In accordance 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 true if an annotation for the specified annotationType is present
* on the supplied clazz and is {@link java.lang.annotation.Inherited inherited}
* @see Class#isAnnotationPresent(Class)
* @see #isAnnotationDeclaredLocally(Class, Class)
*/
public static boolean isAnnotationInherited(Class 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, preserving all attribute types as-is.
* @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 getAnnotationAttributes(Annotation annotation) {
return getAnnotationAttributes(annotation, false);
}
/**
* Retrieve the given annotation's attributes as a Map.
* @param annotation the annotation to retrieve the attributes for
* @param classValuesAsString whether to turn Class references into Strings (for compatibility with
* {@link org.springframework.core.type.AnnotationMetadata} or to preserve them as Class references
* @return the Map of annotation attributes, with attribute names as keys and
* corresponding attribute values as values
*/
public static Map getAnnotationAttributes(Annotation annotation, boolean classValuesAsString) {
Map attrs = new HashMap();
Method[] methods = annotation.annotationType().getDeclaredMethods();
for (Method method : methods) {
if (method.getParameterTypes().length == 0 && method.getReturnType() != void.class) {
try {
Object value = method.invoke(annotation);
if (classValuesAsString) {
if (value instanceof Class) {
value = ((Class) value).getName();
}
else if (value instanceof Class[]) {
Class[] clazzArray = (Class[]) value;
String[] newValue = new String[clazzArray.length];
for (int i = 0; i < clazzArray.length; i++) {
newValue[i] = clazzArray[i].getName();
}
value = newValue;
}
}
attrs.put(method.getName(), value);
}
catch (Exception ex) {
throw new IllegalStateException("Could not obtain annotation attribute values", ex);
}
}
}
return attrs;
}
/**
* Retrieve the value of the "value" 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 null if not found
* @see #getValue(Annotation, String)
*/
public static Object getValue(Annotation annotation) {
return getValue(annotation, VALUE);
}
/**
* Retrieve the value of a named Annotation attribute, given an annotation instance.
* @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 null if not found
* @see #getValue(Annotation)
*/
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 default value of the "value" 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 null if not found
* @see #getDefaultValue(Annotation, String)
*/
public static Object getDefaultValue(Annotation annotation) {
return getDefaultValue(annotation, VALUE);
}
/**
* Retrieve the default value 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 null if not found
* @see #getDefaultValue(Class, String)
*/
public static Object getDefaultValue(Annotation annotation, String attributeName) {
return getDefaultValue(annotation.annotationType(), attributeName);
}
/**
* Retrieve the default value of the "value" attribute
* of a single-element Annotation, given the {@link Class annotation type}.
* @param annotationType the annotation type for which the default value should be retrieved
* @return the default value, or null if not found
* @see #getDefaultValue(Class, String)
*/
public static Object getDefaultValue(Class annotationType) {
return getDefaultValue(annotationType, VALUE);
}
/**
* Retrieve the default value of a named Annotation attribute, given the {@link Class annotation type}.
* @param annotationType the annotation type 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 null if not found
* @see #getDefaultValue(Annotation, String)
*/
public static Object getDefaultValue(Class annotationType, String attributeName) {
try {
Method method = annotationType.getDeclaredMethod(attributeName, new Class[0]);
return method.getDefaultValue();
}
catch (Exception ex) {
return null;
}
}
}