io.github.pustike.inject.utils.AnnotationUtils Maven / Gradle / Ivy
Show all versions of pustike-inject Show documentation
/*
* Copyright (C) 2016-2018 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
*
* https://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 io.github.pustike.inject.utils;
import java.lang.annotation.Annotation;
import java.lang.reflect.InaccessibleObjectException;
import java.lang.reflect.Method;
import java.util.Arrays;
/**
* Helper methods for working with {@link Annotation} instances. This class contains
* various utility methods that make working with annotations simpler.
*
* {@link Annotation} instances are always proxy objects; unfortunately
* dynamic proxies cannot be depended upon to know how to implement certain
* methods in the same manner as would be done by "natural" {@link Annotation}s.
* The methods presented in this class can be used to avoid that possibility. It
* is of course also possible for dynamic proxies to actually delegate their
* e.g. {@link Annotation#equals(Object)}/{@link Annotation#hashCode()}/
* {@link Annotation#toString()} implementations to {@link AnnotationUtils}.
*
* From: commons-lang/src/main/java/org/apache/commons/lang3/AnnotationUtils.java
*/
public final class AnnotationUtils {
/**
* Generate a hash code for the given annotation type with its default attribute values
* using the algorithm presented in the {@link Annotation#hashCode()} API docs.
* @param annotationType the annotation type
* @return the calculated hash code
* @throws RuntimeException if an {@code Exception} is encountered during annotation member access
* @throws IllegalStateException if an annotation method invocation returns {@code null}
*/
public static int hashCode(Class annotationType) {
int result = 0;
for (Method method : annotationType.getDeclaredMethods()) {
if (method.getParameterTypes().length != 0 || method.getReturnType() == void.class) {
continue;// continue if the supplied {@code method} is not an annotation attribute method.
}
try {
Object value = method.getDefaultValue();
if (value == null) {
throw new IllegalStateException(String.format("Annotation method %s returned null", method));
}
result += hashMember(method.getName(), value);
} catch (RuntimeException ex) {
throw ex;
} catch (Exception ex) {
throw new RuntimeException(ex);
}
}
return result;
}
/**
* Generate a hash code for the given annotation using the algorithm
* presented in the {@link Annotation#hashCode()} API docs.
* @param annotation the Annotation for a hash code calculation is desired, not {@code null}
* @return the calculated hash code
* @throws RuntimeException if an {@code Exception} is encountered during annotation member access
* @throws IllegalStateException if an annotation method invocation returns {@code null}
*/
private static int hashCode(Annotation annotation) {
int result = 0;
Class annotationType = annotation.annotationType();
for (Method method : annotationType.getDeclaredMethods()) {
if (method.getParameterTypes().length != 0 || method.getReturnType() == void.class) {
continue;// continue if the supplied {@code method} is not an annotation attribute method.
}
try {
if (!method.trySetAccessible()) {
throw new InaccessibleObjectException("couldn't enable access to annotation method: " + method);
}
Object value = method.invoke(annotation);
if (value == null) {
throw new IllegalStateException(String.format("Annotation method %s returned null", method));
}
result += hashMember(method.getName(), value);
} catch (RuntimeException ex) {
throw ex;
} catch (Exception ex) {
throw new RuntimeException(ex);
}
}
return result;
}
/**
* Helper method for generating a hash code for a member of an annotation.
* @param name the name of the member
* @param value the value of the member
* @return a hash code for this member
*/
private static int hashMember(final String name, final Object value) {
final int part1 = name.hashCode() * 127;
if (value.getClass().isArray()) {
return part1 ^ arrayMemberHash(value.getClass().getComponentType(), value);
}
if (value instanceof Annotation) {
return part1 ^ hashCode((Annotation) value);
}
return part1 ^ value.hashCode();
}
/**
* Helper method for generating a hash code for an array.
* @param componentType the component type of the array
* @param o the array
* @return a hash code for the specified array
*/
private static int arrayMemberHash(final Class componentType, final Object o) {
if (componentType.equals(Byte.TYPE)) {
return Arrays.hashCode((byte[]) o);
}
if (componentType.equals(Short.TYPE)) {
return Arrays.hashCode((short[]) o);
}
if (componentType.equals(Integer.TYPE)) {
return Arrays.hashCode((int[]) o);
}
if (componentType.equals(Character.TYPE)) {
return Arrays.hashCode((char[]) o);
}
if (componentType.equals(Long.TYPE)) {
return Arrays.hashCode((long[]) o);
}
if (componentType.equals(Float.TYPE)) {
return Arrays.hashCode((float[]) o);
}
if (componentType.equals(Double.TYPE)) {
return Arrays.hashCode((double[]) o);
}
if (componentType.equals(Boolean.TYPE)) {
return Arrays.hashCode((boolean[]) o);
}
return Arrays.hashCode((Object[]) o);
}
private AnnotationUtils(){
}
}