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