Java tutorial
package com.github.valdr.thirdparty.spring; /* * This class was copied and modified from the Spring framework. Thanks! */ /* * Copyright 2002-2013 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. */ import java.lang.annotation.Annotation; import java.lang.reflect.AnnotatedElement; import java.lang.reflect.Method; import java.util.List; import java.util.Map; import java.util.WeakHashMap; /** * 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., {@code #findAnnotation(java.lang.reflect.Method, * Class)}, {@code * #getAnnotation(java.lang.reflect.Method, Class)}, and {@code #getAnnotations(java.lang.reflect.Method)}) instead of * the plain annotation lookup * methods in the JDK. You can still explicitly choose between lookup on the given class level only ({@code * #getAnnotation(java.lang.reflect.Method, Class)}) and lookup in the entire inheritance hierarchy of the given method ({@link * #findAnnotation(java.lang.reflect.Method, Class)}). * * @author Rob Harrop * @author Juergen Hoeller * @author Sam Brannen * @author Mark Fisher * @author Chris Beams * @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<Class<?>, Boolean> annotatedInterfaceCache = new WeakHashMap<Class<?>, Boolean>(); /** * Get a single {@link java.lang.annotation.Annotation} of {@code annotationType} from the supplied * Method, Constructor or Field. Meta-annotations will be searched if the annotation * is not declared locally on the supplied element. * @param ae the Method, Constructor or Field from which to get the annotation * @param annotationType the annotation class to look for, both locally and as a meta-annotation * @return the matching annotation or {@code null} if not found * @since 3.1 */ public static <T extends Annotation> T getAnnotation(AnnotatedElement ae, Class<T> annotationType) { T ann = ae.getAnnotation(annotationType); if (ann == null) { for (Annotation metaAnn : ae.getAnnotations()) { ann = metaAnn.annotationType().getAnnotation(annotationType); if (ann != null) { break; } } } return ann; } /** * Get a single {@link java.lang.annotation.Annotation} of {@code annotationType} from the supplied {@link java.lang.reflect.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. * @param method the method to look for annotations on * @param annotationType the annotation class to look for * @return the annotation found, or {@code null} if none found */ public static <A extends Annotation> A findAnnotation(Method method, Class<A> annotationType) { A annotation = getAnnotation(method, annotationType); Class<?> clazz = method.getDeclaringClass(); if (annotation == null) { annotation = searchOnInterfaces(method, annotationType, clazz.getInterfaces()); } while (annotation == null) { clazz = clazz.getSuperclass(); if (clazz == null || clazz.equals(Object.class)) { break; } try { Method equivalentMethod = clazz.getDeclaredMethod(method.getName(), method.getParameterTypes()); annotation = getAnnotation(equivalentMethod, annotationType); } catch (NoSuchMethodException ex) { // No equivalent method found } if (annotation == null) { annotation = searchOnInterfaces(method, annotationType, clazz.getInterfaces()); } } return annotation; } private static <A extends Annotation> A searchOnInterfaces(Method method, Class<A> 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 java.lang.annotation.Annotation} of {@code annotationType} from the supplied {@link Class}, * traversing its interfaces and superclasses 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} if none found */ public static <A extends Annotation> A findAnnotation(Class<?> clazz, Class<A> annotationType) { 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.equals(Object.class)) { return null; } return findAnnotation(superClass, annotationType); } /** * Find the first {@link Class} in the inheritance hierarchy of the specified {@code clazz} * (including the specified {@code clazz} itself) which declares an annotation for the * specified {@code annotationType}, or {@code null} if not found. If the supplied * {@code clazz} is {@code null}, {@code null} will be returned. * <p>If the supplied {@code clazz} 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 java.lang.annotation.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} * @return the first {@link Class} in the inheritance hierarchy of the specified {@code clazz} * which declares an annotation for the specified {@code annotationType}, or {@code null} * if not found * @see Class#isAnnotationPresent(Class) * @see Class#getDeclaredAnnotations() * @see #findAnnotationDeclaringClassForTypes(java.util.List, Class) * @see #isAnnotationDeclaredLocally(Class, Class) */ public static Class<?> findAnnotationDeclaringClass(Class<? extends Annotation> annotationType, Class<?> clazz) { if (clazz == null || clazz.equals(Object.class)) { return null; } return (isAnnotationDeclaredLocally(annotationType, clazz)) ? clazz : findAnnotationDeclaringClass(annotationType, clazz.getSuperclass()); } /** * Find the first {@link Class} in the inheritance hierarchy of the specified * {@code clazz} (including the specified {@code clazz} itself) which declares * at least one of the specified {@code annotationTypes}, or {@code null} if * none of the specified annotation types could be found. * <p>If the supplied {@code clazz} is {@code null}, {@code null} will be * returned. * <p>If the supplied {@code clazz} 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 one of several * candidate {@linkplain java.lang.annotation.Annotation annotations}, so we need to handle this * explicitly. * @param annotationTypes the list of Class objects corresponding to the * annotation types * @param clazz the Class object corresponding to the class on which to check * for the annotations, or {@code null} * @return the first {@link Class} in the inheritance hierarchy of the specified * {@code clazz} which declares an annotation of at least one of the specified * {@code annotationTypes}, or {@code null} if not found * @since 3.2.2 * @see Class#isAnnotationPresent(Class) * @see Class#getDeclaredAnnotations() * @see #findAnnotationDeclaringClass(Class, Class) * @see #isAnnotationDeclaredLocally(Class, Class) */ public static Class<?> findAnnotationDeclaringClassForTypes(List<Class<? extends Annotation>> annotationTypes, Class<?> clazz) { if (clazz == null || clazz.equals(Object.class)) { return null; } for (Class<? extends Annotation> annotationType : annotationTypes) { if (isAnnotationDeclaredLocally(annotationType, clazz)) { return clazz; } } return findAnnotationDeclaringClassForTypes(annotationTypes, clazz.getSuperclass()); } /** * Determine whether an annotation for the specified {@code annotationType} is * declared locally on the supplied {@code clazz}. The supplied {@link Class} * may represent any type. * <p>Note: This method does <strong>not</strong> determine if the annotation is * {@linkplain 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} if an annotation for the specified {@code annotationType} * is declared locally on the supplied {@code clazz} * @see Class#getDeclaredAnnotations() * @see #isAnnotationInherited(Class, Class) */ public static boolean isAnnotationDeclaredLocally(Class<? extends Annotation> annotationType, Class<?> clazz) { boolean declaredLocally = false; for (Annotation annotation : clazz.getDeclaredAnnotations()) { if (annotation.annotationType().equals(annotationType)) { declaredLocally = true; break; } } return declaredLocally; } /** * Determine whether an annotation for the specified {@code annotationType} is present * on the supplied {@code clazz} and is {@linkplain java.lang.annotation.Inherited inherited} * (i.e., not declared locally for the class). * <p>If the supplied {@code 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 {@linkplain java.lang.annotation.Inherited Javadoc} for the * {@code @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} if an annotation for the specified {@code annotationType} is present * on the supplied {@code clazz} and is <em>inherited</em> * @see Class#isAnnotationPresent(Class) * @see #isAnnotationDeclaredLocally(Class, Class) */ public static boolean isAnnotationInherited(Class<? extends Annotation> annotationType, Class<?> clazz) { return (clazz.isAnnotationPresent(annotationType) && !isAnnotationDeclaredLocally(annotationType, clazz)); } /** * Retrieve the given annotation's attributes as a Map, preserving all attribute types * as-is. * <p>Note: As of Spring 3.1.1, the returned map is actually an * {@code org.springframework.core.annotation.AnnotationAttributes} instance, however the Map signature of this * methodhas * been preserved for binary compatibility. * @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) { return getAnnotationAttributes(annotation, false, false); } /** * Retrieve the given annotation's attributes as a Map. Equivalent to calling * {@link #getAnnotationAttributes(java.lang.annotation.Annotation, boolean, boolean)} with * the {@code nestedAnnotationsAsMap} parameter set to {@code false}. * <p>Note: As of Spring 3.1.1, the returned map is actually an * {@code org.springframework.core.annotation.AnnotationAttributes} instance, however the Map signature of this * methodhas * been preserved for binary compatibility. * @param annotation the annotation to retrieve the attributes for * @param classValuesAsString whether to turn Class references into Strings (for * compatibility with {@code 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<String, Object> getAnnotationAttributes(Annotation annotation, boolean classValuesAsString) { return getAnnotationAttributes(annotation, classValuesAsString, false); } /** * Retrieve the given annotation's attributes as an {@code org.springframework.core.annotation.AnnotationAttributes} * map structure. Implemented in Spring 3.1.1 to provide fully recursive annotation * reading capabilities on par with that of the reflection-based * {@code org.springframework.core.type.StandardAnnotationMetadata}. * @param annotation the annotation to retrieve the attributes for * @param classValuesAsString whether to turn Class references into Strings (for * compatibility with {@code org.springframework.core.type.AnnotationMetadata} or to * preserve them as Class references * @param nestedAnnotationsAsMap whether to turn nested Annotation instances into * {@code org.springframework.core.annotation.AnnotationAttributes} maps (for compatibility with * {@code org.springframework.core.type.AnnotationMetadata} or to preserve them as * Annotation instances * @return the annotation attributes (a specialized Map) with attribute names as keys * and corresponding attribute values as values * @since 3.1.1 */ public static AnnotationAttributes getAnnotationAttributes(Annotation annotation, boolean classValuesAsString, boolean nestedAnnotationsAsMap) { AnnotationAttributes attrs = new AnnotationAttributes(); 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; } } if (nestedAnnotationsAsMap && value instanceof Annotation) { attrs.put(method.getName(), getAnnotationAttributes((Annotation) value, classValuesAsString, nestedAnnotationsAsMap)); } else if (nestedAnnotationsAsMap && value instanceof Annotation[]) { Annotation[] realAnnotations = (Annotation[]) value; AnnotationAttributes[] mappedAnnotations = new AnnotationAttributes[realAnnotations.length]; for (int i = 0; i < realAnnotations.length; i++) { mappedAnnotations[i] = getAnnotationAttributes(realAnnotations[i], classValuesAsString, nestedAnnotationsAsMap); } attrs.put(method.getName(), mappedAnnotations); } else { attrs.put(method.getName(), value); } } catch (Exception ex) { throw new IllegalStateException("Could not obtain annotation attribute values", ex); } } } return attrs; } /** * Retrieve the <em>value</em> of the {@code "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 {@code null} if not found * @see #getValue(java.lang.annotation.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. * @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} if not found * @see #getValue(java.lang.annotation.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 <em>default value</em> of the {@code "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 {@code null} if not found * @see #getDefaultValue(java.lang.annotation.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} 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"} 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} 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} if not found * @see #getDefaultValue(java.lang.annotation.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; } } }