com.devsmart.miniweb.AnnotationUtils Maven / Gradle / Ivy
package com.devsmart.miniweb;
import java.lang.annotation.Annotation;
import java.lang.reflect.AnnotatedElement;
import java.lang.reflect.Method;
import java.util.Arrays;
import java.util.Map;
import java.util.WeakHashMap;
public class AnnotationUtils {
/** The attribute name for annotations with a single element */
static final String VALUE = "value";
private static final Map, Boolean> annotatedInterfaceCache = new WeakHashMap, Boolean>();
/**
* Get a single {@link 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 getAnnotation(AnnotatedElement ae, Class 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 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 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;
}
}
}