Source code
Description: source: package: org.apache.commons.lang3.builder, class: ReflectionDiffBuilder, class: Builder

    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;
    022
    023import org.apache.commons.lang3.ArraySorter;
    024import org.apache.commons.lang3.ArrayUtils;
    025import org.apache.commons.lang3.ClassUtils;
    026import org.apache.commons.lang3.reflect.FieldUtils;
    027
    028/**
    029 * Assists in implementing {@link Diffable#diff(Object)} methods.
    030 *
    031 * <p>
    032 * All non-static, non-transient fields (including inherited fields) of the objects to diff are discovered using reflection and compared for differences.
    033 * </p>
    034 *
    035 * <p>
    036 * To use this class, write code as follows:
    037 * </p>
    038 *
    039 * <pre>{@code
    040 * public class Person implements Diffable<Person> {
    041 *   String name;
    042 *   int age;
    043 *   boolean smoker;
    044 *   ...
    045 *
    046 *   public DiffResult<Person> diff(Person obj) {
    047 *     // No need for null check, as NullPointerException correct if obj is null
    048 *     return ReflectionDiffBuilder.<Person>builder()
    049 *       .setDiffBuilder(DiffBuilder.<Person>builder()
    050 *           .setLeft(this)
    051 *           .setRight(obj)
    052 *           .setStyle(ToStringStyle.SHORT_PREFIX_STYLE)
    053 *           .build())
    054 *       .setExcludeFieldNames("userName", "password")
    055 *       .build()  // -> ReflectionDiffBuilder
    056 *       .build(); // -> DiffResult
    057 *   }
    058 * }
    059 * }</pre>
    060 *
    061 * <p>
    062 * The {@link ToStringStyle} passed to the constructor is embedded in the returned {@link DiffResult} and influences the style of the
    063 * {@code DiffResult.toString()} method. This style choice can be overridden by calling {@link DiffResult#toString(ToStringStyle)}.
    064 * </p>
    065 * <p>
    066 * See {@link DiffBuilder} for a non-reflection based version of this class.
    067 * </p>
    068 *
    069 * @param <T> type of the left and right object to diff.
    070 * @see Diffable
    071 * @see Diff
    072 * @see DiffResult
    073 * @see ToStringStyle
    074 * @see DiffBuilder
    075 * @since 3.6
    076 */
    077public class ReflectionDiffBuilder<T> implements Builder<DiffResult<T>> {
    078
    079    /**
    080     * Constructs a new instance.
    081     *
    082     * @param <T> type of the left and right object.
    083     * @since 3.15.0
    084     */
    085    public static final class Builder<T> {
    086
    087        private String[] excludeFieldNames = ArrayUtils.EMPTY_STRING_ARRAY;
    088        private DiffBuilder<T> diffBuilder;
    089
    090        /**
    091         * Constructs a new instance.
    092         */
    093        public Builder() {
    094            // empty
    095        }
    096
    097        /**
    098         * Builds a new configured {@link ReflectionDiffBuilder}.
    099         *
    100         * @return a new configured {@link ReflectionDiffBuilder}.
    101         */
    102        public ReflectionDiffBuilder<T> build() {
    103            return new ReflectionDiffBuilder<>(diffBuilder, excludeFieldNames);
    104        }
    105
    106        /**
    107         * Sets the DiffBuilder.
    108         *
    109         * @param diffBuilder the DiffBuilder.
    110         * @return {@code this} instance.
    111         */
    112        public Builder<T> setDiffBuilder(final DiffBuilder<T> diffBuilder) {
    113            this.diffBuilder = diffBuilder;
    114            return this;
    115        }
    116
    117        /**
    118         * Sets field names to exclude from output. Intended for fields like {@code "password"} or {@code "lastModificationDate"}.
    119         *
    120         * @param excludeFieldNames field names to exclude.
    121         * @return {@code this} instance.
    122         */
    123        public Builder<T> setExcludeFieldNames(final String... excludeFieldNames) {
    124            this.excludeFieldNames = toExcludeFieldNames(excludeFieldNames);
    125            return this;
    126        }
    127
    128    }
    129
    130    /**
    131     * Constructs a new {@link Builder}.
    132     *
    133     * @param <T> type of the left and right object.
    134     * @return a new {@link Builder}.
    135     * @since 3.15.0
    136     */
    137    public static <T> Builder<T> builder() {
    138        return new Builder<>();
    139    }
    140
    141    private static String[] toExcludeFieldNames(final String[] excludeFieldNames) {
    142        if (excludeFieldNames == null) {
    143            return ArrayUtils.EMPTY_STRING_ARRAY;
    144        }
    145        // clone and remove nulls
    146        return ArraySorter.sort(ReflectionToStringBuilder.toNoNullStringArray(excludeFieldNames));
    147    }
    148
    149    private final DiffBuilder<T> diffBuilder;
    150
    151    /**
    152     * Field names to exclude from output. Intended for fields like {@code "password"} or {@code "lastModificationDate"}.
    153     */
    154    private String[] excludeFieldNames;
    155
    156    private ReflectionDiffBuilder(final DiffBuilder<T> diffBuilder, final String[] excludeFieldNames) {
    157        this.diffBuilder = diffBuilder;
    158        this.excludeFieldNames = excludeFieldNames;
    159    }
    160
    161    /**
    162     * Constructs a builder for the specified objects with the specified style.
    163     *
    164     * <p>
    165     * 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
    166     * {@link DiffResult} when {@link #build()} is executed.
    167     * </p>
    168     *
    169     * @param left  {@code this} object.
    170     * @param right the object to diff against.
    171     * @param style the style will use when outputting the objects, {@code null} uses the default
    172     * @throws IllegalArgumentException if {@code left} or {@code right} is {@code null}.
    173     * @deprecated Use {@link Builder}.
    174     */
    175    @Deprecated
    176    public ReflectionDiffBuilder(final T left, final T right, final ToStringStyle style) {
    177        this(DiffBuilder.<T>builder().setLeft(left).setRight(right).setStyle(style).build(), null);
    178    }
    179
    180    private boolean accept(final Field field) {
    181        if (field.getName().indexOf(ClassUtils.INNER_CLASS_SEPARATOR_CHAR) != -1) {
    182            return false;
    183        }
    184        if (Modifier.isTransient(field.getModifiers())) {
    185            return false;
    186        }
    187        if (Modifier.isStatic(field.getModifiers())) {
    188            return false;
    189        }
    190        if (this.excludeFieldNames != null && Arrays.binarySearch(this.excludeFieldNames, field.getName()) >= 0) {
    191            // Reject fields from the getExcludeFieldNames list.
    192            return false;
    193        }
    194        return !field.isAnnotationPresent(DiffExclude.class);
    195    }
    196
    197    /**
    198     * Appends fields using reflection.
    199     *
    200     * @throws SecurityException if an underlying accessible object's method denies the request.
    201     * @see SecurityManager#checkPermission
    202     */
    203    private void appendFields(final Class<?> clazz) {
    204        for (final Field field : FieldUtils.getAllFields(clazz)) {
    205            if (accept(field)) {
    206                try {
    207                    diffBuilder.append(field.getName(), readField(field, getLeft()), readField(field, getRight()));
    208                } catch (final IllegalAccessException e) {
    209                    // this can't happen. Would get a Security exception instead
    210                    // throw a runtime exception in case the impossible happens.
    211                    throw new IllegalArgumentException("Unexpected IllegalAccessException: " + e.getMessage(), e);
    212                }
    213            }
    214        }
    215    }
    216
    217    /**
    218     * {@inheritDoc}
    219     *
    220     * @throws SecurityException if an underlying accessible object's method denies the request.
    221     * @see SecurityManager#checkPermission
    222     */
    223    @Override
    224    public DiffResult<T> build() {
    225        if (getLeft().equals(getRight())) {
    226            return diffBuilder.build();
    227        }
    228        appendFields(getLeft().getClass());
    229        return diffBuilder.build();
    230    }
    231
    232    /**
    233     * Gets the field names that should be excluded from the diff.
    234     *
    235     * @return the excludeFieldNames.
    236     * @since 3.13.0
    237     */
    238    public String[] getExcludeFieldNames() {
    239        return this.excludeFieldNames.clone();
    240    }
    241
    242    private T getLeft() {
    243        return diffBuilder.getLeft();
    244    }
    245
    246    private T getRight() {
    247        return diffBuilder.getRight();
    248    }
    249
    250    /**
    251     * Reads a {@link Field}, forcing access if needed.
    252     *
    253     * @param field  the field to use.
    254     * @param target the object to call on, may be {@code null} for {@code static} fields.
    255     * @return the field value.
    256     * @throws NullPointerException   if the field is {@code null}.
    257     * @throws IllegalAccessException if the field is not made accessible.
    258     * @throws SecurityException      if an underlying accessible object's method denies the request.
    259     * @see SecurityManager#checkPermission
    260     */
    261    private Object readField(final Field field, final Object target) throws IllegalAccessException {
    262        return FieldUtils.readField(field, target, true);
    263    }
    264
    265    /**
    266     * Sets the field names to exclude.
    267     *
    268     * @param excludeFieldNames The field names to exclude from the diff or {@code null}.
    269     * @return {@code this} instance.
    270     * @since 3.13.0
    271     * @deprecated Use {@link Builder#setExcludeFieldNames(String[])}.
    272     */
    273    @Deprecated
    274    public ReflectionDiffBuilder<T> setExcludeFieldNames(final String... excludeFieldNames) {
    275        this.excludeFieldNames = toExcludeFieldNames(excludeFieldNames);
    276        return this;
    277    }
    278
    279}