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.lang.reflect.Type;
20
21 import org.apache.commons.lang3.ObjectUtils;
22 import org.apache.commons.lang3.reflect.TypeUtils;
23 import org.apache.commons.lang3.tuple.Pair;
24
25 /**
26 * A {@link Diff} contains the differences between two {@link Diffable} class
27 * fields.
28 *
29 * <p>
30 * Typically, {@link Diff}s are retrieved by using a {@link DiffBuilder} to
31 * produce a {@link DiffResult}, containing the differences between two objects.
32 * </p>
33 *
34 * @param <T>
35 * The type of object contained within this {@link Diff}. Differences
36 * between primitive objects are stored as their Object wrapper
37 * equivalent.
38 * @since 3.3
39 */
40 public abstract class Diff<T> extends Pair<T, T> {
41
42 private static final long serialVersionUID = 1L;
43
44 /** The field type. */
45 private final Type type;
46
47 /** The field name. */
48 private final String fieldName;
49
50 /**
51 * Constructs a new {@link Diff} for the given field name.
52 *
53 * @param fieldName
54 * the field name
55 */
56 protected Diff(final String fieldName) {
57 this.type = ObjectUtils.defaultIfNull(
58 TypeUtils.getTypeArguments(getClass(), Diff.class).get(
59 Diff.class.getTypeParameters()[0]), Object.class);
60 this.fieldName = fieldName;
61 }
62
63 /**
64 * Gets the name of the field.
65 *
66 * @return the field name
67 */
68 public final String getFieldName() {
69 return fieldName;
70 }
71
72 /**
73 * Gets the type of the field.
74 *
75 * @return the field type
76 */
77 public final Type getType() {
78 return type;
79 }
80
81 /**
82 * Throws {@link UnsupportedOperationException}.
83 *
84 * @param value
85 * ignored
86 * @return nothing
87 */
88 @Override
89 public final T setValue(final T value) {
90 throw new UnsupportedOperationException("Cannot alter Diff object.");
91 }
92
93 /**
94 * Returns a {@link String} representation of the {@link Diff}, with the
95 * following format:
96 *
97 * <pre>
98 * [fieldname: left-value, right-value]
99 * </pre>
100 *
101 * @return the string representation
102 */
103 @Override
104 public final String toString() {
105 return String.format("[%s: %s, %s]", fieldName, getLeft(), getRight());
106 }
107 }