1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.lang3.builder;
18
19 import java.util.Collections;
20 import java.util.Iterator;
21 import java.util.List;
22 import java.util.Objects;
23
24 /**
25 * A {@link DiffResult} contains a collection of the differences between two
26 * {@link Diffable} objects. Typically these differences are displayed using
27 * {@link #toString()} method, which returns a string describing the fields that
28 * differ between the objects.
29 *
30 * <p>
31 * Use a {@link DiffBuilder} to build a {@link DiffResult} comparing two objects.
32 * </p>
33 * @param <T> type of the left and right object.
34 *
35 * @since 3.3
36 */
37 public class DiffResult<T> implements Iterable<Diff<?>> {
38
39 /**
40 * The {@link String} returned when the objects have no differences:
41 * {@value}
42 *
43 */
44 public static final String OBJECTS_SAME_STRING = "";
45
46 private static final String DIFFERS_STRING = "differs from";
47
48 private final List<Diff<?>> diffList;
49 private final T lhs;
50 private final T rhs;
51 private final ToStringStyle style;
52
53 /**
54 * Creates a {@link DiffResult} containing the differences between two
55 * objects.
56 *
57 * @param lhs
58 * the left-hand object
59 * @param rhs
60 * the right-hand object
61 * @param diffList
62 * the list of differences, may be empty
63 * @param style
64 * the style to use for the {@link #toString()} method. May be
65 * {@code null}, in which case
66 * {@link ToStringStyle#DEFAULT_STYLE} is used
67 * @throws NullPointerException if {@code lhs}, {@code rhs} or {@code diffs} is {@code null}
68 */
69 DiffResult(final T lhs, final T rhs, final List<Diff<?>> diffList,
70 final ToStringStyle style) {
71 Objects.requireNonNull(lhs, "lhs");
72 Objects.requireNonNull(rhs, "rhs");
73 Objects.requireNonNull(diffList, "diffList");
74
75 this.diffList = diffList;
76 this.lhs = lhs;
77 this.rhs = rhs;
78
79 if (style == null) {
80 this.style = ToStringStyle.DEFAULT_STYLE;
81 } else {
82 this.style = style;
83 }
84 }
85
86 /**
87 * Returns an unmodifiable list of {@link Diff}s. The list may be empty if
88 * there were no differences between the objects.
89 *
90 * @return an unmodifiable list of {@link Diff}s
91 */
92 public List<Diff<?>> getDiffs() {
93 return Collections.unmodifiableList(diffList);
94 }
95
96 /**
97 * Returns the object the right object has been compared to.
98 *
99 * @return the left object of the diff
100 * @since 3.10
101 */
102 public T getLeft() {
103 return this.lhs;
104 }
105
106 /**
107 * Returns the number of differences between the two objects.
108 *
109 * @return the number of differences
110 */
111 public int getNumberOfDiffs() {
112 return diffList.size();
113 }
114
115 /**
116 * Returns the object the left object has been compared to.
117 *
118 * @return the right object of the diff
119 * @since 3.10
120 */
121 public T getRight() {
122 return this.rhs;
123 }
124
125 /**
126 * Returns the style used by the {@link #toString()} method.
127 *
128 * @return the style
129 */
130 public ToStringStyle getToStringStyle() {
131 return style;
132 }
133
134 /**
135 * Returns an iterator over the {@link Diff} objects contained in this list.
136 *
137 * @return the iterator
138 */
139 @Override
140 public Iterator<Diff<?>> iterator() {
141 return diffList.iterator();
142 }
143
144 /**
145 * Builds a {@link String} description of the differences contained within
146 * this {@link DiffResult}. A {@link ToStringBuilder} is used for each object
147 * and the style of the output is governed by the {@link ToStringStyle}
148 * passed to the constructor.
149 *
150 * <p>
151 * If there are no differences stored in this list, the method will return
152 * {@link #OBJECTS_SAME_STRING}. Otherwise, using the example given in
153 * {@link Diffable} and {@link ToStringStyle#SHORT_PREFIX_STYLE}, an output
154 * might be:
155 * </p>
156 *
157 * <pre>
158 * Person[name=John Doe,age=32] differs from Person[name=Joe Bloggs,age=26]
159 * </pre>
160 *
161 * <p>
162 * This indicates that the objects differ in name and age, but not in
163 * smoking status.
164 * </p>
165 *
166 * <p>
167 * To use a different {@link ToStringStyle} for an instance of this class,
168 * use {@link #toString(ToStringStyle)}.
169 * </p>
170 *
171 * @return a {@link String} description of the differences.
172 */
173 @Override
174 public String toString() {
175 return toString(style);
176 }
177
178 /**
179 * Builds a {@link String} description of the differences contained within
180 * this {@link DiffResult}, using the supplied {@link ToStringStyle}.
181 *
182 * @param style
183 * the {@link ToStringStyle} to use when outputting the objects
184 *
185 * @return a {@link String} description of the differences.
186 */
187 public String toString(final ToStringStyle style) {
188 if (diffList.isEmpty()) {
189 return OBJECTS_SAME_STRING;
190 }
191
192 final ToStringBuilder lhsBuilder = new ToStringBuilder(lhs, style);
193 final ToStringBuilder rhsBuilder = new ToStringBuilder(rhs, style);
194
195 diffList.forEach(diff -> {
196 lhsBuilder.append(diff.getFieldName(), diff.getLeft());
197 rhsBuilder.append(diff.getFieldName(), diff.getRight());
198 });
199
200 return String.format("%s %s %s", lhsBuilder.build(), DIFFERS_STRING, rhsBuilder.build());
201 }
202 }