1 /*
2 * Copyright (c) 2014, 2025, 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 jdk.internal.jrtfs;
26
27 import java.io.IOException;
28 import java.net.URISyntaxException;
29 import java.net.URL;
30 import java.nio.file.Files;
31 import java.nio.file.FileSystem;
32 import java.nio.file.FileSystems;
33 import java.nio.file.FileSystemNotFoundException;
34 import java.nio.file.Path;
35 import java.nio.file.Paths;
36 import java.security.AccessController;
37 import java.security.CodeSource;
38 import java.security.PrivilegedAction;
39
40 import jdk.internal.jimage.ImageReader;
41 import jdk.internal.jimage.ImageReader.Node;
42 import jdk.internal.jimage.PreviewMode;
43
44 /**
45 * @implNote This class needs to maintain JDK 8 source compatibility.
46 *
47 * It is used internally in the JDK to implement jimage/jrtfs access,
48 * but also compiled and delivered as part of the jrtfs.jar to support access
49 * to the jimage file provided by the shipped JDK by tools running on JDK 8.
50 */
51 @SuppressWarnings({"removal", "suppression"})
52 public abstract class SystemImage implements AutoCloseable {
53
54 public abstract Node findNode(String path) throws IOException;
55 public abstract byte[] getResource(Node node) throws IOException;
56 public abstract void close() throws IOException;
57
58 /**
59 * Opens the system image for the current runtime.
60 *
61 * @param mode determines whether preview mode should be enabled.
62 * @return a new system image based on either the jimage file or an "exploded"
63 * modules directory, according to the build state.
64 */
65 public static SystemImage open(PreviewMode mode) throws IOException {
66 return modulesImageExists ? fromJimage(moduleImageFile, mode) : fromDirectory(explodedModulesDir, mode);
67 }
68
69 /** Internal factory method for testing only, use {@link SystemImage#open(PreviewMode)}. */
70 public static SystemImage fromJimage(Path path, PreviewMode mode) throws IOException {
71 final ImageReader image = ImageReader.open(path, mode);
72 return new SystemImage() {
73 @Override
74 public Node findNode(String path) throws IOException {
75 return image.findNode(path);
76 }
77 @Override
78 public byte[] getResource(Node node) throws IOException {
79 return image.getResource(node);
80 }
81 @Override
82 public void close() throws IOException {
83 image.close();
84 }
85 };
86 }
87
88 /** Internal factory method for testing only, use {@link SystemImage#open(PreviewMode)}. */
89 public static SystemImage fromDirectory(Path modulesDir, PreviewMode mode) throws IOException {
90 if (!Files.isDirectory(modulesDir)) {
91 throw new FileSystemNotFoundException(modulesDir.toString());
92 }
93 return new ExplodedImage(modulesDir, mode.isPreviewModeEnabled());
94 }
95
96 private static final String RUNTIME_HOME;
97 // "modules" jimage file Path
98 private static final Path moduleImageFile;
99 // "modules" jimage exists or not?
100 private static final boolean modulesImageExists;
101 // <JAVA_HOME>/modules directory Path
102 private static final Path explodedModulesDir;
103
104 static {
105 PrivilegedAction<String> pa = SystemImage::findHome;
106 RUNTIME_HOME = AccessController.doPrivileged(pa);
107
108 FileSystem fs = FileSystems.getDefault();
109 moduleImageFile = fs.getPath(RUNTIME_HOME, "lib", "modules");
110 explodedModulesDir = fs.getPath(RUNTIME_HOME, "modules");
111
112 modulesImageExists = AccessController.doPrivileged(
113 new PrivilegedAction<Boolean>() {
114 @Override
115 public Boolean run() {
116 return Files.isRegularFile(moduleImageFile);
117 }
118 });
119 }
120
121 /**
122 * Returns the appropriate JDK home for this usage of the FileSystemProvider.
123 * When the CodeSource is null (null loader) then jrt:/ is the current runtime,
124 * otherwise the JDK home is located relative to jrt-fs.jar.
125 */
126 private static String findHome() {
127 CodeSource cs = SystemImage.class.getProtectionDomain().getCodeSource();
128 if (cs == null)
129 return System.getProperty("java.home");
130
131 // assume loaded from $TARGETJDK/lib/jrt-fs.jar
132 URL url = cs.getLocation();
133 if (!url.getProtocol().equalsIgnoreCase("file"))
134 throw new InternalError(url + " loaded in unexpected way");
135 try {
136 Path lib = Paths.get(url.toURI()).getParent();
137 if (!lib.getFileName().toString().equals("lib"))
138 throw new InternalError(url + " unexpected path");
139
140 return lib.getParent().toString();
141 } catch (URISyntaxException e) {
142 throw new InternalError(e);
143 }
144 }
145 }