    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 *
    036 * @since 3.3
    037 */
    038public class DiffResult implements Iterable<Diff<?>> {
    039
    040    /**
    041     * <p>
    042     * The {@code String} returned when the objects have no differences:
    043     * {@value}
    044     * </p>
    045     */
    046    public static final String OBJECTS_SAME_STRING = "";
    047
    048    private static final String DIFFERS_STRING = "differs from";
    049
    050    private final List<Diff<?>> diffs;
    051    private final Object lhs;
    052    private final Object rhs;
    053    private final ToStringStyle style;
    054
    055    /**
    056     * <p>
    057     * Creates a {@link DiffResult} containing the differences between two
    058     * objects.
    059     * </p>
    060     *
    061     * @param lhs
    062     *            the left hand object
    063     * @param rhs
    064     *            the right hand object
    065     * @param diffs
    066     *            the list of differences, may be empty
    067     * @param style
    068     *            the style to use for the {@link #toString()} method. May be
    069     *            {@code null}, in which case
    070     *            {@link ToStringStyle#DEFAULT_STYLE} is used
    071     * @throws IllegalArgumentException
    072     *             if {@code lhs}, {@code rhs} or {@code diffs} is {@code null}
    073     */
    074    DiffResult(final Object lhs, final Object rhs, final List<Diff<?>> diffs,
    075            final ToStringStyle style) {
    076        Validate.isTrue(lhs != null, "Left hand object cannot be null");
    077        Validate.isTrue(rhs != null, "Right hand object cannot be null");
    078        Validate.isTrue(diffs != null, "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>
    093     * Returns an unmodifiable list of {@code Diff}s. The list may be empty if
    094     * there were no differences between the objects.
    095     * </p>
    096     *
    097     * @return an unmodifiable list of {@code Diff}s
    098     */
    099    public List<Diff<?>> getDiffs() {
    100        return Collections.unmodifiableList(diffs);
    101    }
    102
    103    /**
    104     * <p>
    105     * Returns the number of differences between the two objects.
    106     * </p>
    107     *
    108     * @return the number of differences
    109     */
    110    public int getNumberOfDiffs() {
    111        return diffs.size();
    112    }
    113
    114    /**
    115     * <p>
    116     * Returns the style used by the {@link #toString()} method.
    117     * </p>
    118     *
    119     * @return the style
    120     */
    121    public ToStringStyle getToStringStyle() {
    122        return style;
    123    }
    124
    125    /**
    126     * <p>
    127     * Builds a {@code String} description of the differences contained within
    128     * this {@code DiffResult}. A {@link ToStringBuilder} is used for each object
    129     * and the style of the output is governed by the {@code ToStringStyle}
    130     * passed to the constructor.
    131     * </p>
    132     *
    133     * <p>
    134     * If there are no differences stored in this list, the method will return
    135     * {@link #OBJECTS_SAME_STRING}. Otherwise, using the example given in
    136     * {@link Diffable} and {@link ToStringStyle#SHORT_PREFIX_STYLE}, an output
    137     * might be:
    138     * </p>
    139     *
    140     * <pre>
    141     * Person[name=John Doe,age=32] differs from Person[name=Joe Bloggs,age=26]
    142     * </pre>
    143     *
    144     * <p>
    145     * This indicates that the objects differ in name and age, but not in
    146     * smoking status.
    147     * </p>
    148     *
    149     * <p>
    150     * To use a different {@code ToStringStyle} for an instance of this class,
    151     * use {@link #toString(ToStringStyle)}.
    152     * </p>
    153     *
    154     * @return a {@code String} description of the differences.
    155     */
    156    @Override
    157    public String toString() {
    158        return toString(style);
    159    }
    160
    161    /**
    162     * <p>
    163     * Builds a {@code String} description of the differences contained within
    164     * this {@code DiffResult}, using the supplied {@code ToStringStyle}.
    165     * </p>
    166     *
    167     * @param style
    168     *            the {@code ToStringStyle} to use when outputting the objects
    169     *
    170     * @return a {@code String} description of the differences.
    171     */
    172    public String toString(final ToStringStyle style) {
    173        if (diffs.isEmpty()) {
    174            return OBJECTS_SAME_STRING;
    175        }
    176
    177        final ToStringBuilder lhsBuilder = new ToStringBuilder(lhs, style);
    178        final ToStringBuilder rhsBuilder = new ToStringBuilder(rhs, style);
    179
    180        for (final Diff<?> diff : diffs) {
    181            lhsBuilder.append(diff.getFieldName(), diff.getLeft());
    182            rhsBuilder.append(diff.getFieldName(), diff.getRight());
    183        }
    184
    185        return String.format("%s %s %s", lhsBuilder.build(), DIFFERS_STRING,
    186                rhsBuilder.build());
    187    }
    188
    189    /**
    190     * <p>
    191     * Returns an iterator over the {@code Diff} objects contained in this list.
    192     * </p>
    193     *
    194     * @return the iterator
    195     */
    196    @Override
    197    public Iterator<Diff<?>> iterator() {
    198        return diffs.iterator();
    199    }
    200}