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
023/**
024 * <p>
025 * A {@code DiffResult} contains a collection of the differences between two
026 * {@link Diffable} objects. Typically these differences are displayed using
027 * {@link #toString()} method, which returns a string describing the fields that
028 * differ between the objects.
029 * </p>
030 * <p>
031 * Use a {@link DiffBuilder} to build a {@code DiffResult} comparing two objects.
032 * </p>
033 * 
034 * @since 3.3
035 * @version $Id: DiffResult.java 1561225 2014-01-24 23:17:29Z djones $
036 */
037public class DiffResult implements Iterable<Diff<?>> {
038
039    /**
040     * <p>
041     * The {@code String} returned when the objects have no differences:
042     * {@value}
043     * </p>
044     */
045    public static final String OBJECTS_SAME_STRING = "";
046
047    private static final String DIFFERS_STRING = "differs from";
048
049    private final List<Diff<?>> diffs;
050    private final Object lhs;
051    private final Object rhs;
052    private final ToStringStyle style;
053
054    /**
055     * <p>
056     * Creates a {@link DiffResult} containing the differences between two
057     * objects.
058     * </p>
059     * 
060     * @param lhs
061     *            the left hand object
062     * @param rhs
063     *            the right hand object
064     * @param diffs
065     *            the list of differences, may be empty
066     * @param style
067     *            the style to use for the {@link #toString()} method. May be
068     *            {@code null}, in which case
069     *            {@link ToStringStyle#DEFAULT_STYLE} is used
070     * @throws IllegalArgumentException
071     *             if {@code lhs}, {@code rhs} or {@code diffs} is {@code null}
072     */
073    DiffResult(final Object lhs, final Object rhs, final List<Diff<?>> diffs,
074            final ToStringStyle style) {
075        if (lhs == null) {
076            throw new IllegalArgumentException(
077                    "Left hand object cannot be null");
078        }
079        if (rhs == null) {
080            throw new IllegalArgumentException(
081                    "Right hand object cannot be null");
082        }
083        if (diffs == null) {
084            throw new IllegalArgumentException(
085                    "List of differences cannot be null");
086        }
087
088        this.diffs = diffs;
089        this.lhs = lhs;
090        this.rhs = rhs;
091
092        if (style == null) {
093            this.style = ToStringStyle.DEFAULT_STYLE;
094        } else {
095            this.style = style;
096        }
097    }
098
099    /**
100     * <p>
101     * Returns an unmodifiable list of {@code Diff}s. The list may be empty if
102     * there were no differences between the objects.
103     * </p>
104     * 
105     * @return an unmodifiable list of {@code Diff}s
106     */
107    public List<Diff<?>> getDiffs() {
108        return Collections.unmodifiableList(diffs);
109    }
110
111    /**
112     * <p>
113     * Returns the number of differences between the two objects.
114     * </p>
115     * 
116     * @return the number of differences
117     */
118    public int getNumberOfDiffs() {
119        return diffs.size();
120    }
121
122    /**
123     * <p>
124     * Returns the style used by the {@link #toString()} method.
125     * </p>
126     * 
127     * @return the style
128     */
129    public ToStringStyle getToStringStyle() {
130        return style;
131    }
132
133    /**
134     * <p>
135     * Builds a {@code String} description of the differences contained within
136     * this {@code DiffResult}. A {@link ToStringBuilder} is used for each object
137     * and the style of the output is governed by the {@code ToStringStyle}
138     * passed to the constructor.
139     * </p>
140     * 
141     * <p>
142     * If there are no differences stored in this list, the method will return
143     * {@link #OBJECTS_SAME_STRING}. Otherwise, using the example given in
144     * {@link Diffable} and {@link ToStringStyle#SHORT_PREFIX_STYLE}, an output
145     * might be:
146     * </p>
147     * 
148     * <pre>
149     * Person[name=John Doe,age=32] differs from Person[name=Joe Bloggs,age=26]
150     * </pre>
151     * 
152     * <p>
153     * This indicates that the objects differ in name and age, but not in
154     * smoking status.
155     * </p>
156     * 
157     * <p>
158     * To use a different {@code ToStringStyle} for an instance of this class,
159     * use {@link #toString(ToStringStyle)}.
160     * </p>
161     * 
162     * @return a {@code String} description of the differences.
163     */
164    @Override
165    public String toString() {
166        return toString(style);
167    }
168
169    /**
170     * <p>
171     * Builds a {@code String} description of the differences contained within
172     * this {@code DiffResult}, using the supplied {@code ToStringStyle}.
173     * </p>
174     * 
175     * @param style
176     *            the {@code ToStringStyle} to use when outputting the objects
177     * 
178     * @return a {@code String} description of the differences.
179     */
180    public String toString(ToStringStyle style) {
181        if (diffs.size() == 0) {
182            return OBJECTS_SAME_STRING;
183        }
184
185        ToStringBuilder lhsBuilder = new ToStringBuilder(lhs, style);
186        ToStringBuilder rhsBuilder = new ToStringBuilder(rhs, style);
187
188        for (Diff<?> diff : diffs) {
189            lhsBuilder.append(diff.getFieldName(), diff.getLeft());
190            rhsBuilder.append(diff.getFieldName(), diff.getRight());
191        }
192
193        return String.format("%s %s %s", lhsBuilder.build(), DIFFERS_STRING,
194                rhsBuilder.build());
195    }
196
197    /**
198     * <p>
199     * Returns an iterator over the {@code Diff} objects contained in this list.
200     * </p>
201     * 
202     * @return the iterator
203     */
204    @Override
205    public Iterator<Diff<?>> iterator() {
206        return diffs.iterator();
207    }
208}