1 /* 2 * Copyright (c) 2015, 2016, 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 26 package jdk.internal.jimage; 27 28 import java.io.IOException; 29 import java.io.UncheckedIOException; 30 import java.nio.file.Path; 31 import java.nio.file.Paths; 32 import java.util.concurrent.ConcurrentHashMap; 33 import java.util.Map; 34 35 /** 36 * Factory to get ImageReader 37 * 38 * @implNote This class needs to maintain JDK 8 source compatibility. 39 * 40 * It is used internally in the JDK to implement jimage/jrtfs access, 41 * but also compiled and delivered as part of the jrtfs.jar to support access 42 * to the jimage file provided by the shipped JDK by tools running on JDK 8. 43 */ 44 public class ImageReaderFactory { 45 private ImageReaderFactory() {} 46 47 private static final String JAVA_HOME = System.getProperty("java.home"); 48 private static final Path BOOT_MODULES_JIMAGE = 49 Paths.get(JAVA_HOME, "lib", "modules"); 50 51 private static final Map<Path, ImageReader> readers = new ConcurrentHashMap<>(); 52 53 /** 54 * Returns an {@code ImageReader} to read from the given image file 55 */ 56 public static ImageReader get(Path jimage) throws IOException { 57 ImageReader reader = readers.get(jimage); 58 if (reader != null) { 59 return reader; 60 } 61 reader = ImageReader.open(jimage); 62 // potential race with other threads opening the same URL 63 ImageReader r = readers.putIfAbsent(jimage, reader); 64 if (r == null) { 65 return reader; 66 } else { 67 reader.close(); 68 return r; 69 } 70 } 71 72 /** 73 * Returns the {@code ImageReader} to read the image file in this 74 * run-time image. 75 * 76 * @throws UncheckedIOException if an I/O error occurs 77 */ 78 public static ImageReader getImageReader() { 79 try { 80 return get(BOOT_MODULES_JIMAGE); 81 } catch (IOException ioe) { 82 throw new UncheckedIOException(ioe); 83 } 84 } 85 }