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 *      https://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.builder;
018
019import java.lang.reflect.Field;
020import java.lang.reflect.Modifier;
021import java.util.Arrays;
022import java.util.HashSet;
023import java.util.Objects;
024import java.util.Set;
025
026import org.apache.commons.lang3.ArraySorter;
027import org.apache.commons.lang3.ArrayUtils;
028import org.apache.commons.lang3.ClassUtils;
029import org.apache.commons.lang3.reflect.FieldUtils;
030import org.apache.commons.lang3.tuple.Pair;
031
032/**
033 * Assists in implementing {@link Diffable#diff(Object)} methods.
034 *
035 * <p>
036 * All non-static, non-transient fields (including inherited fields) of the objects to diff are discovered using reflection and compared for differences.
037 * </p>
038 *
039 * <p>
040 * To use this class, write code as follows:
041 * </p>
042 *
043 * <pre>{@code
044 * public class Person implements Diffable<Person> {
045 *   String name;
046 *   int age;
047 *   boolean smoker;
048 *   ...
049 *
050 *   public DiffResult<Person> diff(Person obj) {
051 *     // No need for null check, as NullPointerException correct if obj is null
052 *     return ReflectionDiffBuilder.<Person>builder()
053 *       .setDiffBuilder(DiffBuilder.<Person>builder()
054 *           .setLeft(this)
055 *           .setRight(obj)
056 *           .setStyle(ToStringStyle.SHORT_PREFIX_STYLE)
057 *           .build())
058 *       .setExcludeFieldNames("userName", "password")
059 *       .build()  // -> ReflectionDiffBuilder
060 *       .build(); // -> DiffResult
061 *   }
062 * }
063 * }</pre>
064 *
065 * <p>
066 * The {@link ToStringStyle} passed to the constructor is embedded in the returned {@link DiffResult} and influences the style of the
067 * {@code DiffResult.toString()} method. This style choice can be overridden by calling {@link DiffResult#toString(ToStringStyle)}.
068 * </p>
069 * <p>
070 * See {@link DiffBuilder} for a non-reflection based version of this class.
071 * </p>
072 *
073 * @param <T> type of the left and right object to diff.
074 * @see Diffable
075 * @see Diff
076 * @see DiffResult
077 * @see ToStringStyle
078 * @see DiffBuilder
079 * @see AbstractBuilder#setForceAccessible(boolean)
080 * @since 3.6
081 */
082public class ReflectionDiffBuilder<T> extends AbstractReflection implements Builder<DiffResult<T>> {
083
084    /**
085     * Constructs a new instance.
086     *
087     * @param <T> type of the left and right object.
088     * @since 3.15.0
089     */
090    public static final class Builder<T> extends AbstractBuilder<Builder<T>> {
091
092        private String[] excludeFieldNames = ArrayUtils.EMPTY_STRING_ARRAY;
093        private DiffBuilder<T> diffBuilder;
094
095        /**
096         * Constructs a new instance.
097         */
098        public Builder() {
099            // empty
100        }
101
102        /**
103         * Builds a new configured {@link ReflectionDiffBuilder}.
104         *
105         * @return A new configured {@link ReflectionDiffBuilder}.
106         */
107        public ReflectionDiffBuilder<T> build() {
108            return new ReflectionDiffBuilder<>(this);
109        }
110
111        @Override
112        public ReflectionDiffBuilder<T> get() {
113            return build();
114        }
115
116        /**
117         * Sets the DiffBuilder.
118         *
119         * @param diffBuilder The DiffBuilder.
120         * @return {@code this} instance.
121         */
122        public Builder<T> setDiffBuilder(final DiffBuilder<T> diffBuilder) {
123            this.diffBuilder = diffBuilder;
124            return this;
125        }
126
127        /**
128         * Sets field names to exclude from output. Intended for fields like {@code "password"} or {@code "lastModificationDate"}.
129         *
130         * @param excludeFieldNames field names to exclude.
131         * @return {@code this} instance.
132         */
133        public Builder<T> setExcludeFieldNames(final String... excludeFieldNames) {
134            this.excludeFieldNames = toExcludeFieldNames(excludeFieldNames);
135            return this;
136        }
137
138    }
139
140    /**
141     * A registry of objects to detect cyclical object references, avoid infinite loops, and stack overflows.
142     */
143    private static final ThreadLocal<Set<Pair<IDKey, IDKey>>> REGISTRY = ThreadLocal.withInitial(HashSet::new);
144
145    /**
146     * Constructs a new {@link Builder}.
147     *
148     * @param <T> type of the left and right object.
149     * @return A new {@link Builder}.
150     * @since 3.15.0
151     */
152    public static <T> Builder<T> builder() {
153        return new Builder<>();
154    }
155
156    /**
157     * Gets the registry of object pairs being traversed by the reflection
158     * methods in the current thread.
159     *
160     * @return Set the registry of objects being traversed
161     */
162    static Set<Pair<IDKey, IDKey>> getRegistry() {
163        return REGISTRY.get();
164    }
165
166    /**
167     * Tests whether the registry contains the given object pair.
168     * <p>
169     * Used by the reflection methods to avoid infinite loops.
170     * Objects might be swapped therefore a check is needed if the object pair
171     * is registered in the given or swapped order.
172     * </p>
173     *
174     * @param lhs {@code this} object to lookup in registry
175     * @param rhs The other object to lookup on registry
176     * @return boolean {@code true} if the registry contains the given object.
177     */
178    static boolean isRegistered(final Object lhs, final Object rhs) {
179        return isRegistered(lhs, rhs, getRegistry());
180    }
181
182    /**
183     * Registers the given object pair.
184     * Used by the reflection methods to avoid infinite loops.
185     *
186     * @param lhs {@code this} object to register
187     * @param rhs the other object to register
188     */
189    static void register(final Object lhs, final Object rhs) {
190        register(lhs, rhs, getRegistry());
191    }
192
193    private static String[] toExcludeFieldNames(final String[] excludeFieldNames) {
194        if (excludeFieldNames == null) {
195            return ArrayUtils.EMPTY_STRING_ARRAY;
196        }
197        // clone and remove nulls
198        return ArraySorter.sort(ReflectionToStringBuilder.toNoNullStringArray(excludeFieldNames));
199    }
200
201    /**
202     * Unregisters the given object pair.
203     *
204     * <p>
205     * Used by the reflection methods to avoid infinite loops.
206     * </p>
207     *
208     * @param lhs {@code this} object to unregister
209     * @param rhs the other object to unregister
210     */
211    static void unregister(final Object lhs, final Object rhs) {
212        unregister(lhs, rhs, getRegistry(), REGISTRY);
213    }
214
215    private final DiffBuilder<T> diffBuilder;
216
217    /**
218     * Field names to exclude from output. Intended for fields like {@code "password"} or {@code "lastModificationDate"}.
219     */
220    private String[] excludeFieldNames;
221
222    /**
223     * Constructs a new instance.
224     *
225     * @param builder A non-null Builder.
226     * @throws NullPointerException Thrown on null input.
227     */
228    private ReflectionDiffBuilder(final Builder<T> builder) {
229        super(Objects.requireNonNull(builder, "builder"));
230        this.diffBuilder = Objects.requireNonNull(builder.diffBuilder, "diffBuilder");
231        this.excludeFieldNames = Objects.requireNonNull(builder.excludeFieldNames, "excludeFieldNames");
232    }
233
234    /**
235     * Constructs a new instance.
236     *
237     * @param diffBuilder A non-null DiffBuilder.
238     * @param excludeFieldNames A non-null String array.
239     * @throws NullPointerException Thrown on null input.
240     */
241    private ReflectionDiffBuilder(final DiffBuilder<T> diffBuilder, final String[] excludeFieldNames) {
242        this(ReflectionDiffBuilder.<T>builder().setDiffBuilder(diffBuilder).setExcludeFieldNames(excludeFieldNames));
243    }
244
245    /**
246     * Constructs a builder for the specified objects with the specified style.
247     *
248     * <p>
249     * If {@code left == right} or {@code left.equals(right)} then the builder will not evaluate any calls to {@code append(...)} and will return an empty
250     * {@link DiffResult} when {@link #build()} is executed.
251     * </p>
252     *
253     * @param left  {@code this} object.
254     * @param right The object to diff against.
255     * @param style The style will use when outputting the objects, {@code null} uses the default
256     * @throws IllegalArgumentException Thrown if {@code left} or {@code right} is {@code null}.
257     * @deprecated Use {@link Builder}.
258     */
259    @Deprecated
260    public ReflectionDiffBuilder(final T left, final T right, final ToStringStyle style) {
261        this(DiffBuilder.<T>builder().setLeft(left).setRight(right).setStyle(style).build(), ArrayUtils.EMPTY_STRING_ARRAY);
262    }
263
264    private boolean accept(final Field field) {
265        if (field.getName().indexOf(ClassUtils.INNER_CLASS_SEPARATOR_CHAR) != -1 || Modifier.isTransient(field.getModifiers())
266                || Modifier.isStatic(field.getModifiers()) || Arrays.binarySearch(excludeFieldNames, field.getName()) >= 0) {
267            // Rejected.
268            return false;
269        }
270        return !field.isAnnotationPresent(DiffExclude.class);
271    }
272
273    /**
274     * Appends fields using reflection.
275     *
276     * @throws SecurityException Thrown if an underlying accessible object's method denies the request.
277     * @see SecurityManager#checkPermission
278     */
279    private void appendFields(final Class<?> clazz) {
280        for (final Field field : FieldUtils.getAllFields(clazz)) {
281            if (accept(field)) {
282                try {
283                    if (setAccessible(field)) {
284                        diffBuilder.append(field.getName(), Reflection.getUnchecked(field, getLeft()), Reflection.getUnchecked(field, getRight()));
285                    }
286                } catch (final RuntimeException e) {
287                    // Ignored as per AccessibleObject / SecurityManager / InaccessibleObjectException
288                }
289            }
290        }
291    }
292
293    /**
294     * {@inheritDoc}
295     *
296     * @throws SecurityException Thrown if an underlying accessible object's method denies the request.
297     * @see SecurityManager#checkPermission
298     */
299    @Override
300    public DiffResult<T> build() {
301        if (getLeft() == getRight() || isRegistered(getLeft(), getRight())) {
302            return diffBuilder.build();
303        }
304        try {
305            register(getLeft(), getRight());
306            appendFields(getLeft().getClass());
307            return diffBuilder.build();
308        } finally {
309            unregister(getLeft(), getRight());
310        }
311    }
312
313    /**
314     * Gets the field names that should be excluded from the diff.
315     *
316     * @return The excludeFieldNames.
317     * @since 3.13.0
318     */
319    public String[] getExcludeFieldNames() {
320        return excludeFieldNames.clone();
321    }
322
323    private T getLeft() {
324        return diffBuilder.getLeft();
325    }
326
327    private T getRight() {
328        return diffBuilder.getRight();
329    }
330
331    /**
332     * Sets the field names to exclude.
333     *
334     * @param excludeFieldNames The field names to exclude from the diff or {@code null}.
335     * @return {@code this} instance.
336     * @since 3.13.0
337     * @deprecated Use {@link Builder#setExcludeFieldNames(String[])}.
338     */
339    @Deprecated
340    public ReflectionDiffBuilder<T> setExcludeFieldNames(final String... excludeFieldNames) {
341        this.excludeFieldNames = toExcludeFieldNames(excludeFieldNames);
342        return this;
343    }
344
345}