    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.builder;
    018
    019import java.util.Collections;
    020import java.util.Iterator;
    021import java.util.List;
    022
    023import org.apache.commons.lang3.Validate;
    024
    025/**
    026 * <p>
    027 * A {@code DiffResult} contains a collection of the differences between two
    028 * {@link Diffable} objects. Typically these differences are displayed using
    029 * {@link #toString()} method, which returns a string describing the fields that
    030 * differ between the objects.
    031 * </p>
    032 * <p>
    033 * Use a {@link DiffBuilder} to build a {@code DiffResult} comparing two objects.
    034 * </p>
    035 * @param <T> type of the left and right object.
    036 *
    037 * @since 3.3
    038 */
    039public class DiffResult<T> implements Iterable<Diff<?>> {
    040
    041    /**
    042     * <p>
    043     * The {@code String} returned when the objects have no differences:
    044     * {@value}
    045     * </p>
    046     */
    047    public static final String OBJECTS_SAME_STRING = "";
    048
    049    private static final String DIFFERS_STRING = "differs from";
    050
    051    private final List<Diff<?>> diffs;
    052    private final T lhs;
    053    private final T rhs;
    054    private final ToStringStyle style;
    055
    056    /**
    057     * <p>
    058     * Creates a {@link DiffResult} containing the differences between two
    059     * objects.
    060     * </p>
    061     *
    062     * @param lhs
    063     *            the left hand object
    064     * @param rhs
    065     *            the right hand object
    066     * @param diffs
    067     *            the list of differences, may be empty
    068     * @param style
    069     *            the style to use for the {@link #toString()} method. May be
    070     *            {@code null}, in which case
    071     *            {@link ToStringStyle#DEFAULT_STYLE} is used
    072     * @throws NullPointerException if {@code lhs}, {@code rhs} or {@code diffs} is {@code null}
    073     */
    074    DiffResult(final T lhs, final T rhs, final List<Diff<?>> diffs,
    075            final ToStringStyle style) {
    076        Validate.notNull(lhs, "Left hand object cannot be null");
    077        Validate.notNull(rhs, "Right hand object cannot be null");
    078        Validate.notNull(diffs, "List of differences cannot be null");
    079
    080        this.diffs = diffs;
    081        this.lhs = lhs;
    082        this.rhs = rhs;
    083
    084        if (style == null) {
    085            this.style = ToStringStyle.DEFAULT_STYLE;
    086        } else {
    087            this.style = style;
    088        }
    089    }
    090
    091    /**
    092     * <p>Returns the object the right object has been compared to.</p>
    093     *
    094     * @return the left object of the diff
    095     * @since 3.10
    096     */
    097    public T getLeft() {
    098        return this.lhs;
    099    }
    100
    101    /**
    102     * <p>Returns the object the left object has been compared to.</p>
    103     *
    104     * @return the right object of the diff
    105     * @since 3.10
    106     */
    107    public T getRight() {
    108        return this.rhs;
    109    }
    110
    111    /**
    112     * <p>
    113     * Returns an unmodifiable list of {@code Diff}s. The list may be empty if
    114     * there were no differences between the objects.
    115     * </p>
    116     *
    117     * @return an unmodifiable list of {@code Diff}s
    118     */
    119    public List<Diff<?>> getDiffs() {
    120        return Collections.unmodifiableList(diffs);
    121    }
    122
    123    /**
    124     * <p>
    125     * Returns the number of differences between the two objects.
    126     * </p>
    127     *
    128     * @return the number of differences
    129     */
    130    public int getNumberOfDiffs() {
    131        return diffs.size();
    132    }
    133
    134    /**
    135     * <p>
    136     * Returns the style used by the {@link #toString()} method.
    137     * </p>
    138     *
    139     * @return the style
    140     */
    141    public ToStringStyle getToStringStyle() {
    142        return style;
    143    }
    144
    145    /**
    146     * <p>
    147     * Builds a {@code String} description of the differences contained within
    148     * this {@code DiffResult}. A {@link ToStringBuilder} is used for each object
    149     * and the style of the output is governed by the {@code ToStringStyle}
    150     * passed to the constructor.
    151     * </p>
    152     *
    153     * <p>
    154     * If there are no differences stored in this list, the method will return
    155     * {@link #OBJECTS_SAME_STRING}. Otherwise, using the example given in
    156     * {@link Diffable} and {@link ToStringStyle#SHORT_PREFIX_STYLE}, an output
    157     * might be:
    158     * </p>
    159     *
    160     * <pre>
    161     * Person[name=John Doe,age=32] differs from Person[name=Joe Bloggs,age=26]
    162     * </pre>
    163     *
    164     * <p>
    165     * This indicates that the objects differ in name and age, but not in
    166     * smoking status.
    167     * </p>
    168     *
    169     * <p>
    170     * To use a different {@code ToStringStyle} for an instance of this class,
    171     * use {@link #toString(ToStringStyle)}.
    172     * </p>
    173     *
    174     * @return a {@code String} description of the differences.
    175     */
    176    @Override
    177    public String toString() {
    178        return toString(style);
    179    }
    180
    181    /**
    182     * <p>
    183     * Builds a {@code String} description of the differences contained within
    184     * this {@code DiffResult}, using the supplied {@code ToStringStyle}.
    185     * </p>
    186     *
    187     * @param style
    188     *            the {@code ToStringStyle} to use when outputting the objects
    189     *
    190     * @return a {@code String} description of the differences.
    191     */
    192    public String toString(final ToStringStyle style) {
    193        if (diffs.isEmpty()) {
    194            return OBJECTS_SAME_STRING;
    195        }
    196
    197        final ToStringBuilder lhsBuilder = new ToStringBuilder(lhs, style);
    198        final ToStringBuilder rhsBuilder = new ToStringBuilder(rhs, style);
    199
    200        for (final Diff<?> diff : diffs) {
    201            lhsBuilder.append(diff.getFieldName(), diff.getLeft());
    202            rhsBuilder.append(diff.getFieldName(), diff.getRight());
    203        }
    204
    205        return String.format("%s %s %s", lhsBuilder.build(), DIFFERS_STRING,
    206                rhsBuilder.build());
    207    }
    208
    209    /**
    210     * <p>
    211     * Returns an iterator over the {@code Diff} objects contained in this list.
    212     * </p>
    213     *
    214     * @return the iterator
    215     */
    216    @Override
    217    public Iterator<Diff<?>> iterator() {
    218        return diffs.iterator();
    219    }
    220}