Source code

001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.lang3;
018
019import java.lang.annotation.Annotation;
020import java.lang.reflect.InvocationTargetException;
021import java.lang.reflect.Method;
022import java.util.Arrays;
023
024import org.apache.commons.lang3.builder.ToStringBuilder;
025import org.apache.commons.lang3.builder.ToStringStyle;
026
027/**
028 * <p>Helper methods for working with {@link Annotation} instances.</p>
029 *
030 * <p>This class contains various utility methods that make working with
031 * annotations simpler.</p>
032 *
033 * <p>{@link Annotation} instances are always proxy objects; unfortunately
034 * dynamic proxies cannot be depended upon to know how to implement certain
035 * methods in the same manner as would be done by "natural" {@link Annotation}s.
036 * The methods presented in this class can be used to avoid that possibility. It
037 * is of course also possible for dynamic proxies to actually delegate their
038 * e.g. {@link Annotation#equals(Object)}/{@link Annotation#hashCode()}/
039 * {@link Annotation#toString()} implementations to {@link AnnotationUtils}.</p>
040 *
041 * <p>#ThreadSafe#</p>
042 *
043 * @since 3.0
044 */
045public class AnnotationUtils {
046
047    /**
048     * A style that prints annotations as recommended.
049     */
050    private static final ToStringStyle TO_STRING_STYLE = new ToStringStyle() {
051        /** Serialization version */
052        private static final long serialVersionUID = 1L;
053
054        {
055            setDefaultFullDetail(true);
056            setArrayContentDetail(true);
057            setUseClassName(true);
058            setUseShortClassName(true);
059            setUseIdentityHashCode(false);
060            setContentStart("(");
061            setContentEnd(")");
062            setFieldSeparator(", ");
063            setArrayStart("[");
064            setArrayEnd("]");
065        }
066
067        /**
068         * {@inheritDoc}
069         */
070        @Override
071        protected String getShortClassName(final java.lang.Class<?> cls) {
072            Class<? extends Annotation> annotationType = null;
073            for (final Class<?> iface : ClassUtils.getAllInterfaces(cls)) {
074                if (Annotation.class.isAssignableFrom(iface)) {
075                    @SuppressWarnings("unchecked") // OK because we just checked the assignability
076                    final
077                    Class<? extends Annotation> found = (Class<? extends Annotation>) iface;
078                    annotationType = found;
079                    break;
080                }
081            }
082            return new StringBuilder(annotationType == null ? StringUtils.EMPTY : annotationType.getName())
083                    .insert(0, '@').toString();
084        }
085
086        /**
087         * {@inheritDoc}
088         */
089        @Override
090        protected void appendDetail(final StringBuffer buffer, final String fieldName, Object value) {
091            if (value instanceof Annotation) {
092                value = AnnotationUtils.toString((Annotation) value);
093            }
094            super.appendDetail(buffer, fieldName, value);
095        }
096
097    };
098
099    /**
100     * <p>{@code AnnotationUtils} instances should NOT be constructed in
101     * standard programming. Instead, the class should be used statically.</p>
102     *
103     * <p>This constructor is public to permit tools that require a JavaBean
104     * instance to operate.</p>
105     */
106    public AnnotationUtils() {
107    }
108
109    //-----------------------------------------------------------------------
110    /**
111     * <p>Checks if two annotations are equal using the criteria for equality
112     * presented in the {@link Annotation#equals(Object)} API docs.</p>
113     *
114     * @param a1 the first Annotation to compare, {@code null} returns
115     * {@code false} unless both are {@code null}
116     * @param a2 the second Annotation to compare, {@code null} returns
117     * {@code false} unless both are {@code null}
118     * @return {@code true} if the two annotations are {@code equal} or both
119     * {@code null}
120     */
121    public static boolean equals(final Annotation a1, final Annotation a2) {
122        if (a1 == a2) {
123            return true;
124        }
125        if (a1 == null || a2 == null) {
126            return false;
127        }
128        final Class<? extends Annotation> type = a1.annotationType();
129        final Class<? extends Annotation> type2 = a2.annotationType();
130        Validate.notNull(type, "Annotation %s with null annotationType()", a1);
131        Validate.notNull(type2, "Annotation %s with null annotationType()", a2);
132        if (!type.equals(type2)) {
133            return false;
134        }
135        try {
136            for (final Method m : type.getDeclaredMethods()) {
137                if (m.getParameterTypes().length == 0
138                        && isValidAnnotationMemberType(m.getReturnType())) {
139                    final Object v1 = m.invoke(a1);
140                    final Object v2 = m.invoke(a2);
141                    if (!memberEquals(m.getReturnType(), v1, v2)) {
142                        return false;
143                    }
144                }
145            }
146        } catch (final IllegalAccessException | InvocationTargetException ex) {
147            return false;
148        }
149        return true;
150    }
151
152    /**
153     * <p>Generate a hash code for the given annotation using the algorithm
154     * presented in the {@link Annotation#hashCode()} API docs.</p>
155     *
156     * @param a the Annotation for a hash code calculation is desired, not
157     * {@code null}
158     * @return the calculated hash code
159     * @throws RuntimeException if an {@code Exception} is encountered during
160     * annotation member access
161     * @throws IllegalStateException if an annotation method invocation returns
162     * {@code null}
163     */
164    public static int hashCode(final Annotation a) {
165        int result = 0;
166        final Class<? extends Annotation> type = a.annotationType();
167        for (final Method m : type.getDeclaredMethods()) {
168            try {
169                final Object value = m.invoke(a);
170                if (value == null) {
171                    throw new IllegalStateException(
172                            String.format("Annotation method %s returned null", m));
173                }
174                result += hashMember(m.getName(), value);
175            } catch (final RuntimeException ex) {
176                throw ex;
177            } catch (final Exception ex) {
178                throw new RuntimeException(ex);
179            }
180        }
181        return result;
182    }
183
184    /**
185     * <p>Generate a string representation of an Annotation, as suggested by
186     * {@link Annotation#toString()}.</p>
187     *
188     * @param a the annotation of which a string representation is desired
189     * @return the standard string representation of an annotation, not
190     * {@code null}
191     */
192    public static String toString(final Annotation a) {
193        final ToStringBuilder builder = new ToStringBuilder(a, TO_STRING_STYLE);
194        for (final Method m : a.annotationType().getDeclaredMethods()) {
195            if (m.getParameterTypes().length > 0) {
196                continue; //wtf?
197            }
198            try {
199                builder.append(m.getName(), m.invoke(a));
200            } catch (final RuntimeException ex) {
201                throw ex;
202            } catch (final Exception ex) {
203                throw new RuntimeException(ex);
204            }
205        }
206        return builder.build();
207    }
208
209    /**
210     * <p>Checks if the specified type is permitted as an annotation member.</p>
211     *
212     * <p>The Java language specification only permits certain types to be used
213     * in annotations. These include {@link String}, {@link Class}, primitive
214     * types, {@link Annotation}, {@link Enum}, and single-dimensional arrays of
215     * these types.</p>
216     *
217     * @param type the type to check, {@code null}
218     * @return {@code true} if the type is a valid type to use in an annotation
219     */
220    public static boolean isValidAnnotationMemberType(Class<?> type) {
221        if (type == null) {
222            return false;
223        }
224        if (type.isArray()) {
225            type = type.getComponentType();
226        }
227        return type.isPrimitive() || type.isEnum() || type.isAnnotation()
228                || String.class.equals(type) || Class.class.equals(type);
229    }
230
231    //besides modularity, this has the advantage of autoboxing primitives:
232    /**
233     * Helper method for generating a hash code for a member of an annotation.
234     *
235     * @param name the name of the member
236     * @param value the value of the member
237     * @return a hash code for this member
238     */
239    private static int hashMember(final String name, final Object value) {
240        final int part1 = name.hashCode() * 127;
241        if (value.getClass().isArray()) {
242            return part1 ^ arrayMemberHash(value.getClass().getComponentType(), value);
243        }
244        if (value instanceof Annotation) {
245            return part1 ^ hashCode((Annotation) value);
246        }
247        return part1 ^ value.hashCode();
248    }
249
250    /**
251     * Helper method for checking whether two objects of the given type are
252     * equal. This method is used to compare the parameters of two annotation
253     * instances.
254     *
255     * @param type the type of the objects to be compared
256     * @param o1 the first object
257     * @param o2 the second object
258     * @return a flag whether these objects are equal
259     */
260    private static boolean memberEquals(final Class<?> type, final Object o1, final Object o2) {
261        if (o1 == o2) {
262            return true;
263        }
264        if (o1 == null || o2 == null) {
265            return false;
266        }
267        if (type.isArray()) {
268            return arrayMemberEquals(type.getComponentType(), o1, o2);
269        }
270        if (type.isAnnotation()) {
271            return equals((Annotation) o1, (Annotation) o2);
272        }
273        return o1.equals(o2);
274    }
275
276    /**
277     * Helper method for comparing two objects of an array type.
278     *
279     * @param componentType the component type of the array
280     * @param o1 the first object
281     * @param o2 the second object
282     * @return a flag whether these objects are equal
283     */
284    private static boolean arrayMemberEquals(final Class<?> componentType, final Object o1, final Object o2) {
285        if (componentType.isAnnotation()) {
286            return annotationArrayMemberEquals((Annotation[]) o1, (Annotation[]) o2);
287        }
288        if (componentType.equals(Byte.TYPE)) {
289            return Arrays.equals((byte[]) o1, (byte[]) o2);
290        }
291        if (componentType.equals(Short.TYPE)) {
292            return Arrays.equals((short[]) o1, (short[]) o2);
293        }
294        if (componentType.equals(Integer.TYPE)) {
295            return Arrays.equals((int[]) o1, (int[]) o2);
296        }
297        if (componentType.equals(Character.TYPE)) {
298            return Arrays.equals((char[]) o1, (char[]) o2);
299        }
300        if (componentType.equals(Long.TYPE)) {
301            return Arrays.equals((long[]) o1, (long[]) o2);
302        }
303        if (componentType.equals(Float.TYPE)) {
304            return Arrays.equals((float[]) o1, (float[]) o2);
305        }
306        if (componentType.equals(Double.TYPE)) {
307            return Arrays.equals((double[]) o1, (double[]) o2);
308        }
309        if (componentType.equals(Boolean.TYPE)) {
310            return Arrays.equals((boolean[]) o1, (boolean[]) o2);
311        }
312        return Arrays.equals((Object[]) o1, (Object[]) o2);
313    }
314
315    /**
316     * Helper method for comparing two arrays of annotations.
317     *
318     * @param a1 the first array
319     * @param a2 the second array
320     * @return a flag whether these arrays are equal
321     */
322    private static boolean annotationArrayMemberEquals(final Annotation[] a1, final Annotation[] a2) {
323        if (a1.length != a2.length) {
324            return false;
325        }
326        for (int i = 0; i < a1.length; i++) {
327            if (!equals(a1[i], a2[i])) {
328                return false;
329            }
330        }
331        return true;
332    }
333
334    /**
335     * Helper method for generating a hash code for an array.
336     *
337     * @param componentType the component type of the array
338     * @param o the array
339     * @return a hash code for the specified array
340     */
341    private static int arrayMemberHash(final Class<?> componentType, final Object o) {
342        if (componentType.equals(Byte.TYPE)) {
343            return Arrays.hashCode((byte[]) o);
344        }
345        if (componentType.equals(Short.TYPE)) {
346            return Arrays.hashCode((short[]) o);
347        }
348        if (componentType.equals(Integer.TYPE)) {
349            return Arrays.hashCode((int[]) o);
350        }
351        if (componentType.equals(Character.TYPE)) {
352            return Arrays.hashCode((char[]) o);
353        }
354        if (componentType.equals(Long.TYPE)) {
355            return Arrays.hashCode((long[]) o);
356        }
357        if (componentType.equals(Float.TYPE)) {
358            return Arrays.hashCode((float[]) o);
359        }
360        if (componentType.equals(Double.TYPE)) {
361            return Arrays.hashCode((double[]) o);
362        }
363        if (componentType.equals(Boolean.TYPE)) {
364            return Arrays.hashCode((boolean[]) o);
365        }
366        return Arrays.hashCode((Object[]) o);
367    }
368}