1 /* 2 * ==================================================================== 3 * Licensed to the Apache Software Foundation (ASF) under one 4 * or more contributor license agreements. See the NOTICE file 5 * distributed with this work for additional information 6 * regarding copyright ownership. The ASF licenses this file 7 * to you under the Apache License, Version 2.0 (the 8 * "License"); you may not use this file except in compliance 9 * with the License. You may obtain a copy of the License at 10 * 11 * http://www.apache.org/licenses/LICENSE-2.0 12 * 13 * Unless required by applicable law or agreed to in writing, 14 * software distributed under the License is distributed on an 15 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 16 * KIND, either express or implied. See the License for the 17 * specific language governing permissions and limitations 18 * under the License. 19 * ==================================================================== 20 * 21 * This software consists of voluntary contributions made by many 22 * individuals on behalf of the Apache Software Foundation. For more 23 * information on the Apache Software Foundation, please see 24 * <http://www.apache.org/>. 25 * 26 */ 27 package org.apache.hc.client5.http.cache; 28 29 import org.apache.hc.core5.annotation.Contract; 30 import org.apache.hc.core5.annotation.ThreadingBehavior; 31 32 /** 33 * Atomic Compare-And-Swap (CAS) cache operation. 34 * 35 * @since 5.0 36 */ 37 @Contract(threading = ThreadingBehavior.STATELESS) 38 public interface HttpCacheCASOperation { 39 40 /** 41 * Returns the new cache entry that should replace an existing one. 42 * 43 * @param existing 44 * the cache entry currently in-place in the cache, possibly 45 * {@code null} if nonexistent 46 * @return the cache entry that should replace it, again, 47 * possibly {@code null} if the entry should be deleted 48 */ 49 HttpCacheEntry execute(HttpCacheEntry existing) throws ResourceIOException; 50 51 }