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 Class<?> cls) {
072            for (final Class<?> iface : ClassUtils.getAllInterfaces(cls)) {
073                if (Annotation.class.isAssignableFrom(iface)) {
074                    return "@" + iface.getName();
075                }
076            }
077            return StringUtils.EMPTY;
078        }
079
080        /**
081         * {@inheritDoc}
082         */
083        @Override
084        protected void appendDetail(final StringBuffer buffer, final String fieldName, Object value) {
085            if (value instanceof Annotation) {
086                value = AnnotationUtils.toString((Annotation) value);
087            }
088            super.appendDetail(buffer, fieldName, value);
089        }
090
091    };
092
093    /**
094     * <p>{@code AnnotationUtils} instances should NOT be constructed in
095     * standard programming. Instead, the class should be used statically.</p>
096     *
097     * <p>This constructor is public to permit tools that require a JavaBean
098     * instance to operate.</p>
099     */
100    public AnnotationUtils() {
101    }
102
103    //-----------------------------------------------------------------------
104    /**
105     * <p>Checks if two annotations are equal using the criteria for equality
106     * presented in the {@link Annotation#equals(Object)} API docs.</p>
107     *
108     * @param a1 the first Annotation to compare, {@code null} returns
109     * {@code false} unless both are {@code null}
110     * @param a2 the second Annotation to compare, {@code null} returns
111     * {@code false} unless both are {@code null}
112     * @return {@code true} if the two annotations are {@code equal} or both
113     * {@code null}
114     */
115    public static boolean equals(final Annotation a1, final Annotation a2) {
116        if (a1 == a2) {
117            return true;
118        }
119        if (a1 == null || a2 == null) {
120            return false;
121        }
122        final Class<? extends Annotation> type1 = a1.annotationType();
123        final Class<? extends Annotation> type2 = a2.annotationType();
124        Validate.notNull(type1, "Annotation %s with null annotationType()", a1);
125        Validate.notNull(type2, "Annotation %s with null annotationType()", a2);
126        if (!type1.equals(type2)) {
127            return false;
128        }
129        try {
130            for (final Method m : type1.getDeclaredMethods()) {
131                if (m.getParameterTypes().length == 0
132                        && isValidAnnotationMemberType(m.getReturnType())) {
133                    final Object v1 = m.invoke(a1);
134                    final Object v2 = m.invoke(a2);
135                    if (!memberEquals(m.getReturnType(), v1, v2)) {
136                        return false;
137                    }
138                }
139            }
140        } catch (final IllegalAccessException | InvocationTargetException ex) {
141            return false;
142        }
143        return true;
144    }
145
146    /**
147     * <p>Generate a hash code for the given annotation using the algorithm
148     * presented in the {@link Annotation#hashCode()} API docs.</p>
149     *
150     * @param a the Annotation for a hash code calculation is desired, not
151     * {@code null}
152     * @return the calculated hash code
153     * @throws RuntimeException if an {@code Exception} is encountered during
154     * annotation member access
155     * @throws IllegalStateException if an annotation method invocation returns
156     * {@code null}
157     */
158    public static int hashCode(final Annotation a) {
159        int result = 0;
160        final Class<? extends Annotation> type = a.annotationType();
161        for (final Method m : type.getDeclaredMethods()) {
162            try {
163                final Object value = m.invoke(a);
164                if (value == null) {
165                    throw new IllegalStateException(
166                            String.format("Annotation method %s returned null", m));
167                }
168                result += hashMember(m.getName(), value);
169            } catch (final RuntimeException ex) {
170                throw ex;
171            } catch (final Exception ex) {
172                throw new RuntimeException(ex);
173            }
174        }
175        return result;
176    }
177
178    /**
179     * <p>Generate a string representation of an Annotation, as suggested by
180     * {@link Annotation#toString()}.</p>
181     *
182     * @param a the annotation of which a string representation is desired
183     * @return the standard string representation of an annotation, not
184     * {@code null}
185     */
186    public static String toString(final Annotation a) {
187        final ToStringBuilder builder = new ToStringBuilder(a, TO_STRING_STYLE);
188        for (final Method m : a.annotationType().getDeclaredMethods()) {
189            if (m.getParameterTypes().length > 0) {
190                continue; //wtf?
191            }
192            try {
193                builder.append(m.getName(), m.invoke(a));
194            } catch (final RuntimeException ex) {
195                throw ex;
196            } catch (final Exception ex) {
197                throw new RuntimeException(ex);
198            }
199        }
200        return builder.build();
201    }
202
203    /**
204     * <p>Checks if the specified type is permitted as an annotation member.</p>
205     *
206     * <p>The Java language specification only permits certain types to be used
207     * in annotations. These include {@link String}, {@link Class}, primitive
208     * types, {@link Annotation}, {@link Enum}, and single-dimensional arrays of
209     * these types.</p>
210     *
211     * @param type the type to check, {@code null}
212     * @return {@code true} if the type is a valid type to use in an annotation
213     */
214    public static boolean isValidAnnotationMemberType(Class<?> type) {
215        if (type == null) {
216            return false;
217        }
218        if (type.isArray()) {
219            type = type.getComponentType();
220        }
221        return type.isPrimitive() || type.isEnum() || type.isAnnotation()
222                || String.class.equals(type) || Class.class.equals(type);
223    }
224
225    //besides modularity, this has the advantage of autoboxing primitives:
226    /**
227     * Helper method for generating a hash code for a member of an annotation.
228     *
229     * @param name the name of the member
230     * @param value the value of the member
231     * @return a hash code for this member
232     */
233    private static int hashMember(final String name, final Object value) {
234        final int part1 = name.hashCode() * 127;
235        if (value.getClass().isArray()) {
236            return part1 ^ arrayMemberHash(value.getClass().getComponentType(), value);
237        }
238        if (value instanceof Annotation) {
239            return part1 ^ hashCode((Annotation) value);
240        }
241        return part1 ^ value.hashCode();
242    }
243
244    /**
245     * Helper method for checking whether two objects of the given type are
246     * equal. This method is used to compare the parameters of two annotation
247     * instances.
248     *
249     * @param type the type of the objects to be compared
250     * @param o1 the first object
251     * @param o2 the second object
252     * @return a flag whether these objects are equal
253     */
254    private static boolean memberEquals(final Class<?> type, final Object o1, final Object o2) {
255        if (o1 == o2) {
256            return true;
257        }
258        if (o1 == null || o2 == null) {
259            return false;
260        }
261        if (type.isArray()) {
262            return arrayMemberEquals(type.getComponentType(), o1, o2);
263        }
264        if (type.isAnnotation()) {
265            return equals((Annotation) o1, (Annotation) o2);
266        }
267        return o1.equals(o2);
268    }
269
270    /**
271     * Helper method for comparing two objects of an array type.
272     *
273     * @param componentType the component type of the array
274     * @param o1 the first object
275     * @param o2 the second object
276     * @return a flag whether these objects are equal
277     */
278    private static boolean arrayMemberEquals(final Class<?> componentType, final Object o1, final Object o2) {
279        if (componentType.isAnnotation()) {
280            return annotationArrayMemberEquals((Annotation[]) o1, (Annotation[]) o2);
281        }
282        if (componentType.equals(Byte.TYPE)) {
283            return Arrays.equals((byte[]) o1, (byte[]) o2);
284        }
285        if (componentType.equals(Short.TYPE)) {
286            return Arrays.equals((short[]) o1, (short[]) o2);
287        }
288        if (componentType.equals(Integer.TYPE)) {
289            return Arrays.equals((int[]) o1, (int[]) o2);
290        }
291        if (componentType.equals(Character.TYPE)) {
292            return Arrays.equals((char[]) o1, (char[]) o2);
293        }
294        if (componentType.equals(Long.TYPE)) {
295            return Arrays.equals((long[]) o1, (long[]) o2);
296        }
297        if (componentType.equals(Float.TYPE)) {
298            return Arrays.equals((float[]) o1, (float[]) o2);
299        }
300        if (componentType.equals(Double.TYPE)) {
301            return Arrays.equals((double[]) o1, (double[]) o2);
302        }
303        if (componentType.equals(Boolean.TYPE)) {
304            return Arrays.equals((boolean[]) o1, (boolean[]) o2);
305        }
306        return Arrays.equals((Object[]) o1, (Object[]) o2);
307    }
308
309    /**
310     * Helper method for comparing two arrays of annotations.
311     *
312     * @param a1 the first array
313     * @param a2 the second array
314     * @return a flag whether these arrays are equal
315     */
316    private static boolean annotationArrayMemberEquals(final Annotation[] a1, final Annotation[] a2) {
317        if (a1.length != a2.length) {
318            return false;
319        }
320        for (int i = 0; i < a1.length; i++) {
321            if (!equals(a1[i], a2[i])) {
322                return false;
323            }
324        }
325        return true;
326    }
327
328    /**
329     * Helper method for generating a hash code for an array.
330     *
331     * @param componentType the component type of the array
332     * @param o the array
333     * @return a hash code for the specified array
334     */
335    private static int arrayMemberHash(final Class<?> componentType, final Object o) {
336        if (componentType.equals(Byte.TYPE)) {
337            return Arrays.hashCode((byte[]) o);
338        }
339        if (componentType.equals(Short.TYPE)) {
340            return Arrays.hashCode((short[]) o);
341        }
342        if (componentType.equals(Integer.TYPE)) {
343            return Arrays.hashCode((int[]) o);
344        }
345        if (componentType.equals(Character.TYPE)) {
346            return Arrays.hashCode((char[]) o);
347        }
348        if (componentType.equals(Long.TYPE)) {
349            return Arrays.hashCode((long[]) o);
350        }
351        if (componentType.equals(Float.TYPE)) {
352            return Arrays.hashCode((float[]) o);
353        }
354        if (componentType.equals(Double.TYPE)) {
355            return Arrays.hashCode((double[]) o);
356        }
357        if (componentType.equals(Boolean.TYPE)) {
358            return Arrays.hashCode((boolean[]) o);
359        }
360        return Arrays.hashCode((Object[]) o);
361    }
362}