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Apache Commons Lang, a package of Java utility classes for the
classes that are in java.lang's hierarchy, or are considered to be so
standard as to justify existence in java.lang.
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.apache.commons.lang3;
import java.lang.annotation.Annotation;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Arrays;
import org.apache.commons.lang3.builder.ToStringBuilder;
import org.apache.commons.lang3.builder.ToStringStyle;
/**
* 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}.
*
* #ThreadSafe#
*
* @since 3.0
*/
public class AnnotationUtils {
/**
* A style that prints annotations as recommended.
*/
private static final ToStringStyle TO_STRING_STYLE = new ToStringStyle() {
/** Serialization version */
private static final long serialVersionUID = 1L;
{
setDefaultFullDetail(true);
setArrayContentDetail(true);
setUseClassName(true);
setUseShortClassName(true);
setUseIdentityHashCode(false);
setContentStart("(");
setContentEnd(")");
setFieldSeparator(", ");
setArrayStart("[");
setArrayEnd("]");
}
/**
* {@inheritDoc}
*/
@Override
protected String getShortClassName(final Class cls) {
for (final Class iface : ClassUtils.getAllInterfaces(cls)) {
if (Annotation.class.isAssignableFrom(iface)) {
return "@" + iface.getName();
}
}
return StringUtils.EMPTY;
}
/**
* {@inheritDoc}
*/
@Override
protected void appendDetail(final StringBuffer buffer, final String fieldName, Object value) {
if (value instanceof Annotation) {
value = AnnotationUtils.toString((Annotation) value);
}
super.appendDetail(buffer, fieldName, value);
}
};
/**
* {@code AnnotationUtils} instances should NOT be constructed in
* standard programming. Instead, the class should be used statically.
*
* This constructor is public to permit tools that require a JavaBean
* instance to operate.
*/
public AnnotationUtils() {
}
//-----------------------------------------------------------------------
/**
* Checks if two annotations are equal using the criteria for equality
* presented in the {@link Annotation#equals(Object)} API docs.
*
* @param a1 the first Annotation to compare, {@code null} returns
* {@code false} unless both are {@code null}
* @param a2 the second Annotation to compare, {@code null} returns
* {@code false} unless both are {@code null}
* @return {@code true} if the two annotations are {@code equal} or both
* {@code null}
*/
public static boolean equals(final Annotation a1, final Annotation a2) {
if (a1 == a2) {
return true;
}
if (a1 == null || a2 == null) {
return false;
}
final Class type1 = a1.annotationType();
final Class type2 = a2.annotationType();
Validate.notNull(type1, "Annotation %s with null annotationType()", a1);
Validate.notNull(type2, "Annotation %s with null annotationType()", a2);
if (!type1.equals(type2)) {
return false;
}
try {
for (final Method m : type1.getDeclaredMethods()) {
if (m.getParameterTypes().length == 0
&& isValidAnnotationMemberType(m.getReturnType())) {
final Object v1 = m.invoke(a1);
final Object v2 = m.invoke(a2);
if (!memberEquals(m.getReturnType(), v1, v2)) {
return false;
}
}
}
} catch (final IllegalAccessException | InvocationTargetException ex) {
return false;
}
return true;
}
/**
* Generate a hash code for the given annotation using the algorithm
* presented in the {@link Annotation#hashCode()} API docs.
*
* @param a 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}
*/
public static int hashCode(final Annotation a) {
int result = 0;
final Class type = a.annotationType();
for (final Method m : type.getDeclaredMethods()) {
try {
final Object value = m.invoke(a);
if (value == null) {
throw new IllegalStateException(
String.format("Annotation method %s returned null", m));
}
result += hashMember(m.getName(), value);
} catch (final RuntimeException ex) {
throw ex;
} catch (final Exception ex) {
throw new RuntimeException(ex);
}
}
return result;
}
/**
* Generate a string representation of an Annotation, as suggested by
* {@link Annotation#toString()}.
*
* @param a the annotation of which a string representation is desired
* @return the standard string representation of an annotation, not
* {@code null}
*/
public static String toString(final Annotation a) {
final ToStringBuilder builder = new ToStringBuilder(a, TO_STRING_STYLE);
for (final Method m : a.annotationType().getDeclaredMethods()) {
if (m.getParameterTypes().length > 0) {
continue; //wtf?
}
try {
builder.append(m.getName(), m.invoke(a));
} catch (final RuntimeException ex) {
throw ex;
} catch (final Exception ex) {
throw new RuntimeException(ex);
}
}
return builder.build();
}
/**
* Checks if the specified type is permitted as an annotation member.
*
* The Java language specification only permits certain types to be used
* in annotations. These include {@link String}, {@link Class}, primitive
* types, {@link Annotation}, {@link Enum}, and single-dimensional arrays of
* these types.
*
* @param type the type to check, {@code null}
* @return {@code true} if the type is a valid type to use in an annotation
*/
public static boolean isValidAnnotationMemberType(Class type) {
if (type == null) {
return false;
}
if (type.isArray()) {
type = type.getComponentType();
}
return type.isPrimitive() || type.isEnum() || type.isAnnotation()
|| String.class.equals(type) || Class.class.equals(type);
}
//besides modularity, this has the advantage of autoboxing primitives:
/**
* 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 checking whether two objects of the given type are
* equal. This method is used to compare the parameters of two annotation
* instances.
*
* @param type the type of the objects to be compared
* @param o1 the first object
* @param o2 the second object
* @return a flag whether these objects are equal
*/
private static boolean memberEquals(final Class type, final Object o1, final Object o2) {
if (o1 == o2) {
return true;
}
if (o1 == null || o2 == null) {
return false;
}
if (type.isArray()) {
return arrayMemberEquals(type.getComponentType(), o1, o2);
}
if (type.isAnnotation()) {
return equals((Annotation) o1, (Annotation) o2);
}
return o1.equals(o2);
}
/**
* Helper method for comparing two objects of an array type.
*
* @param componentType the component type of the array
* @param o1 the first object
* @param o2 the second object
* @return a flag whether these objects are equal
*/
private static boolean arrayMemberEquals(final Class componentType, final Object o1, final Object o2) {
if (componentType.isAnnotation()) {
return annotationArrayMemberEquals((Annotation[]) o1, (Annotation[]) o2);
}
if (componentType.equals(Byte.TYPE)) {
return Arrays.equals((byte[]) o1, (byte[]) o2);
}
if (componentType.equals(Short.TYPE)) {
return Arrays.equals((short[]) o1, (short[]) o2);
}
if (componentType.equals(Integer.TYPE)) {
return Arrays.equals((int[]) o1, (int[]) o2);
}
if (componentType.equals(Character.TYPE)) {
return Arrays.equals((char[]) o1, (char[]) o2);
}
if (componentType.equals(Long.TYPE)) {
return Arrays.equals((long[]) o1, (long[]) o2);
}
if (componentType.equals(Float.TYPE)) {
return Arrays.equals((float[]) o1, (float[]) o2);
}
if (componentType.equals(Double.TYPE)) {
return Arrays.equals((double[]) o1, (double[]) o2);
}
if (componentType.equals(Boolean.TYPE)) {
return Arrays.equals((boolean[]) o1, (boolean[]) o2);
}
return Arrays.equals((Object[]) o1, (Object[]) o2);
}
/**
* Helper method for comparing two arrays of annotations.
*
* @param a1 the first array
* @param a2 the second array
* @return a flag whether these arrays are equal
*/
private static boolean annotationArrayMemberEquals(final Annotation[] a1, final Annotation[] a2) {
if (a1.length != a2.length) {
return false;
}
for (int i = 0; i < a1.length; i++) {
if (!equals(a1[i], a2[i])) {
return false;
}
}
return true;
}
/**
* 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);
}
}