001/* 002 * Copyright 2002-2017 the original author or authors. 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * https://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 */ 016 017package org.springframework.cache.support; 018 019import java.io.Serializable; 020 021/** 022 * Simple serializable class that serves as a {@code null} replacement 023 * for cache stores which otherwise do not support {@code null} values. 024 * 025 * @author Juergen Hoeller 026 * @since 4.2.2 027 * @see AbstractValueAdaptingCache 028 */ 029public final class NullValue implements Serializable { 030 031 /** 032 * The canonical representation of a {@code null} replacement, as used by the 033 * default implementation of {@link AbstractValueAdaptingCache#toStoreValue}/ 034 * {@link AbstractValueAdaptingCache#fromStoreValue}. 035 * @since 4.3.10 036 */ 037 public static final Object INSTANCE = new NullValue(); 038 039 private static final long serialVersionUID = 1L; 040 041 042 private NullValue() { 043 } 044 045 private Object readResolve() { 046 return INSTANCE; 047 } 048 049}