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.lang.reflect.Type;
020
021import org.apache.commons.lang3.ObjectUtils;
022import org.apache.commons.lang3.reflect.TypeUtils;
023import org.apache.commons.lang3.tuple.Pair;
024
025/**
026 * <p>
027 * A {@code Diff} contains the differences between two {@link Diffable} class
028 * fields.
029 * </p>
030 * 
031 * <p>
032 * Typically, {@code Diff}s are retrieved by using a {@link DiffBuilder} to
033 * produce a {@link DiffResult}, containing the differences between two objects.
034 * </p>
035 * 
036 * 
037 * @param <T>
038 *            The type of object contained within this {@code Diff}. Differences
039 *            between primitive objects are stored as their Object wrapper
040 *            equivalent.
041 * @since 3.3
042 * @version $Id: Diff.java 1583482 2014-03-31 22:54:57Z niallp $
043 */
044public abstract class Diff<T> extends Pair<T, T> {
045
046    private static final long serialVersionUID = 1L;
047
048    private final Type type;
049    private final String fieldName;
050
051    /**
052     * <p>
053     * Constructs a new {@code Diff} for the given field name.
054     * </p>
055     * 
056     * @param fieldName
057     *            the name of the field
058     */
059    protected Diff(String fieldName) {
060        this.type = ObjectUtils.defaultIfNull(
061                TypeUtils.getTypeArguments(getClass(), Diff.class).get(
062                        Diff.class.getTypeParameters()[0]), Object.class);
063        this.fieldName = fieldName;
064    }
065
066    /**
067     * <p>
068     * Returns the type of the field.
069     * </p>
070     * 
071     * @return the field type
072     */
073    public final Type getType() {
074        return type;
075    }
076
077    /**
078     * <p>
079     * Returns the name of the field.
080     * </p>
081     * 
082     * @return the field name
083     */
084    public final String getFieldName() {
085        return fieldName;
086    }
087
088    /**
089     * <p>
090     * Returns a {@code String} representation of the {@code Diff}, with the
091     * following format:</p>
092     * 
093     * <pre>
094     * [fieldname: left-value, right-value]
095     * </pre>
096     * 
097     * 
098     * @return the string representation
099     */
100    @Override
101    public final String toString() {
102        return String.format("[%s: %s, %s]", fieldName, getLeft(), getRight());
103    }
104
105    /**
106     * <p>
107     * Throws {@code UnsupportedOperationException}.
108     * </p>
109     * 
110     * @param value
111     *            ignored
112     * @return nothing
113     */
114    @Override
115    public final T setValue(T value) {
116        throw new UnsupportedOperationException("Cannot alter Diff object.");
117    }
118}