    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 */
    043public abstract class Diff<T> extends Pair<T, T> {
    044
    045    private static final long serialVersionUID = 1L;
    046
    047    private final Type type;
    048    private final String fieldName;
    049
    050    /**
    051     * <p>
    052     * Constructs a new {@code Diff} for the given field name.
    053     * </p>
    054     *
    055     * @param fieldName
    056     *            the name of the field
    057     */
    058    protected Diff(final String fieldName) {
    059        this.type = ObjectUtils.defaultIfNull(
    060                TypeUtils.getTypeArguments(getClass(), Diff.class).get(
    061                        Diff.class.getTypeParameters()[0]), Object.class);
    062        this.fieldName = fieldName;
    063    }
    064
    065    /**
    066     * <p>
    067     * Returns the type of the field.
    068     * </p>
    069     *
    070     * @return the field type
    071     */
    072    public final Type getType() {
    073        return type;
    074    }
    075
    076    /**
    077     * <p>
    078     * Returns the name of the field.
    079     * </p>
    080     *
    081     * @return the field name
    082     */
    083    public final String getFieldName() {
    084        return fieldName;
    085    }
    086
    087    /**
    088     * <p>
    089     * Returns a {@code String} representation of the {@code Diff}, with the
    090     * following format:</p>
    091     *
    092     * <pre>
    093     * [fieldname: left-value, right-value]
    094     * </pre>
    095     *
    096     *
    097     * @return the string representation
    098     */
    099    @Override
    100    public final String toString() {
    101        return String.format("[%s: %s, %s]", fieldName, getLeft(), getRight());
    102    }
    103
    104    /**
    105     * <p>
    106     * Throws {@code UnsupportedOperationException}.
    107     * </p>
    108     *
    109     * @param value
    110     *            ignored
    111     * @return nothing
    112     */
    113    @Override
    114    public final T setValue(final T value) {
    115        throw new UnsupportedOperationException("Cannot alter Diff object.");
    116    }
    117}