1 /* 2 * Copyright (c) 2005, 2019, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 package java.io; 26 27 import java.util.*; 28 29 import jdk.internal.access.SharedSecrets; 30 31 /** 32 * This class holds a set of filenames to be deleted on VM exit through a shutdown hook. 33 * A set is used both to prevent double-insertion of the same file as well as offer 34 * quick removal. 35 */ 36 37 class DeleteOnExitHook { 38 private static class OrderCount { 39 long order; 40 int count; 41 } 42 private static long nextOrder; 43 private static HashMap<String, OrderCount> files = new HashMap<>(); 44 static { 45 // DeleteOnExitHook must be the last shutdown hook to be invoked. 46 // Application shutdown hooks may add the first file to the 47 // delete on exit list and cause the DeleteOnExitHook to be 48 // registered during shutdown in progress. So set the 49 // registerShutdownInProgress parameter to true. 50 SharedSecrets.getJavaLangAccess() 51 .registerShutdownHook(2 /* Shutdown hook invocation order */, 52 true /* register even if shutdown in progress */, 53 new Runnable() { 54 public void run() { 55 runHooks(); 56 } 57 } 58 ); 59 } 60 61 private DeleteOnExitHook() {} 62 63 static synchronized void deleteOnExit(String file) { 64 if(files == null) { 65 // DeleteOnExitHook is running. Too late to add a file 66 throw new IllegalStateException("Shutdown in progress"); 67 } 68 69 OrderCount oc = files.computeIfAbsent(file, f -> new OrderCount()); 70 oc.order = nextOrder++; 71 oc.count++; 72 } 73 74 static synchronized void cancelDeleteOnExit(String file) { 75 if(files != null) { 76 files.compute(file, (f, oc) -> { 77 if (oc == null) { 78 throw new IllegalStateException( 79 "Unbalanced cancelDeleteOnExit for missing deleteOnExit"); 80 } 81 return --oc.count <= 0 ? null : oc; 82 }); 83 } 84 } 85 86 static void runHooks() { 87 HashMap<String, OrderCount> theFiles; 88 89 synchronized (DeleteOnExitHook.class) { 90 theFiles = files; 91 files = null; 92 } 93 94 theFiles 95 .entrySet() 96 .stream() 97 // last registered -> first deleted 98 .sorted(Comparator.comparing(e -> -e.getValue().order)) 99 .map(e -> new File(e.getKey())) 100 .forEach(File::delete); 101 } 102 }