1 /*
2 * Copyright (c) 2015, 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
26 package jdk.internal.loader;
27
28 import java.io.IOException;
29 import java.net.URL;
30 import java.nio.file.InvalidPathException;
31 import java.nio.file.Path;
32 import java.security.CodeSource;
33 import java.security.PermissionCollection;
34 import java.util.jar.Manifest;
35
36 import jdk.internal.access.JavaLangAccess;
37 import jdk.internal.access.SharedSecrets;
38 import jdk.internal.misc.VM;
39
40 /**
41 * Creates and provides access to the built-in platform and application class
42 * loaders. It also creates the class loader that is used to locate resources
43 * in modules defined to the boot class loader.
44 */
45
46 public class ClassLoaders {
47
48 private ClassLoaders() { }
49
50 private static final JavaLangAccess JLA = SharedSecrets.getJavaLangAccess();
51
52 // the built-in class loaders
53 private static final BootClassLoader BOOT_LOADER;
54 private static final PlatformClassLoader PLATFORM_LOADER;
55 private static final AppClassLoader APP_LOADER;
56
57 // Creates the built-in class loaders.
58 static {
59 // -Xbootclasspath/a or -javaagent with Boot-Class-Path attribute
60 String append = VM.getSavedProperty("jdk.boot.class.path.append");
61 BOOT_LOADER =
62 new BootClassLoader((append != null && !append.isEmpty())
63 ? new URLClassPath(append, true)
64 : null);
65 PLATFORM_LOADER = new PlatformClassLoader(BOOT_LOADER);
66
67 // A class path is required when no initial module is specified.
68 // In this case the class path defaults to "", meaning the current
69 // working directory. When an initial module is specified, on the
70 // contrary, we drop this historic interpretation of the empty
71 // string and instead treat it as unspecified.
72 String cp = System.getProperty("java.class.path");
73 if (cp == null || cp.isEmpty()) {
74 String initialModuleName = System.getProperty("jdk.module.main");
75 cp = (initialModuleName == null) ? "" : null;
76 }
77 URLClassPath ucp = new URLClassPath(cp, false);
78 APP_LOADER = new AppClassLoader(PLATFORM_LOADER, ucp);
79 }
80
81 /**
82 * Returns the class loader that is used to find resources in modules
83 * defined to the boot class loader.
84 *
85 * @apiNote This method is not public, it should instead be used via
86 * the BootLoader class that provides a restricted API to this class
87 * loader.
88 */
89 static BuiltinClassLoader bootLoader() {
90 return BOOT_LOADER;
91 }
92
93 /**
94 * Returns the platform class loader.
95 */
96 public static ClassLoader platformClassLoader() {
97 return PLATFORM_LOADER;
98 }
99
100 /**
101 * Returns the application class loader.
102 */
103 public static ClassLoader appClassLoader() {
104 return APP_LOADER;
105 }
106
107 /**
108 * The class loader that is used to find resources in modules defined to
109 * the boot class loader. It is not used for class loading.
110 */
111 private static class BootClassLoader extends BuiltinClassLoader {
112 BootClassLoader(URLClassPath bcp) {
113 super(null, null, bcp);
114 }
115
116 @Override
117 protected Class<?> loadClassOrNull(String cn, boolean resolve) {
118 return JLA.findBootstrapClassOrNull(this, cn);
119 }
120 };
121
122 /**
123 * The platform class loader, a unique type to make it easier to distinguish
124 * from the application class loader.
125 */
126 private static class PlatformClassLoader extends BuiltinClassLoader {
127 static {
128 if (!ClassLoader.registerAsParallelCapable())
129 throw new InternalError();
130 }
131
132 PlatformClassLoader(BootClassLoader parent) {
133 super("platform", parent, null);
134 }
135 }
136
137 /**
138 * The application class loader that is a {@code BuiltinClassLoader} with
139 * customizations to be compatible with long standing behavior.
140 */
141 private static class AppClassLoader extends BuiltinClassLoader {
142 static {
143 if (!ClassLoader.registerAsParallelCapable())
144 throw new InternalError();
145 }
146
147 final URLClassPath ucp;
148
149 AppClassLoader(PlatformClassLoader parent, URLClassPath ucp) {
150 super("app", parent, ucp);
151 this.ucp = ucp;
152 }
153
154 @Override
155 protected Class<?> loadClass(String cn, boolean resolve)
156 throws ClassNotFoundException
157 {
158 // for compatibility reasons, say where restricted package list has
159 // been updated to list API packages in the unnamed module.
160 SecurityManager sm = System.getSecurityManager();
161 if (sm != null) {
162 int i = cn.lastIndexOf('.');
163 if (i != -1) {
164 sm.checkPackageAccess(cn.substring(0, i));
165 }
166 }
167
168 return super.loadClass(cn, resolve);
169 }
170
171 @Override
172 protected PermissionCollection getPermissions(CodeSource cs) {
173 PermissionCollection perms = super.getPermissions(cs);
174 perms.add(new RuntimePermission("exitVM"));
175 return perms;
176 }
177
178 /**
179 * Called by the VM to support dynamic additions to the class path
180 *
181 * @see java.lang.instrument.Instrumentation#appendToSystemClassLoaderSearch
182 */
183 void appendToClassPathForInstrumentation(String path) {
184 ucp.addFile(path);
185 }
186
187 /**
188 * Called by the VM to support define package for AppCDS
189 */
190 protected Package defineOrCheckPackage(String pn, Manifest man, URL url) {
191 return super.defineOrCheckPackage(pn, man, url);
192 }
193 }
194
195 /**
196 * Attempts to convert the given string to a file URL.
197 *
198 * @apiNote This is called by the VM
199 */
200 @Deprecated
201 private static URL toFileURL(String s) {
202 try {
203 // Use an intermediate File object to construct a URI/URL without
204 // authority component as URLClassPath can't handle URLs with a UNC
205 // server name in the authority component.
206 return Path.of(s).toRealPath().toFile().toURI().toURL();
207 } catch (InvalidPathException | IOException ignore) {
208 // malformed path string or class path element does not exist
209 return null;
210 }
211 }
212 }