1 /*
2 * Copyright (c) 2015, 2017, 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.Paths;
32 import java.security.CodeSource;
33 import java.security.PermissionCollection;
34 import java.util.jar.Manifest;
35
36 import jdk.internal.misc.JavaLangAccess;
37 import jdk.internal.misc.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 public class ClassLoaders {
46
47 private ClassLoaders() { }
48
49 private static final JavaLangAccess JLA = SharedSecrets.getJavaLangAccess();
50
51 // the built-in class loaders
52 private static final BootClassLoader BOOT_LOADER;
53 private static final PlatformClassLoader PLATFORM_LOADER;
54 private static final AppClassLoader APP_LOADER;
55
56 // Creates the built-in class loaders.
57 static {
58 // -Xbootclasspath/a or -javaagent with Boot-Class-Path attribute
59 String s = VM.getSavedProperty("jdk.boot.class.path.append");
60 BOOT_LOADER = new BootClassLoader((s != null && s.length() > 0)
61 ? new URLClassPath(s, true)
62 : null);
63 PLATFORM_LOADER = new PlatformClassLoader(BOOT_LOADER);
64
65 // A class path is required when no main module is specified.
66 // In this case the class path defaults to "", meaning the
67 // current working directory. When a main module is specified,
68 // on the contrary, we drop this historic interpretation of
69 // the empty string and instead treat it as unspecified.
70 String cp = System.getProperty("java.class.path");
71 if (cp == null || cp.length() == 0) {
72 String mainMid = System.getProperty("jdk.module.main");
73 cp = (mainMid == null) ? "" : null;
74 }
75 URLClassPath ucp = new URLClassPath(cp, false);
76 APP_LOADER = new AppClassLoader(PLATFORM_LOADER, ucp);
77 }
78
79 /**
80 * Returns the class loader that is used to find resources in modules
81 * defined to the boot class loader.
82 *
83 * @apiNote This method is not public, it should instead be used via
84 * the BootLoader class that provides a restricted API to this class
85 * loader.
86 */
87 static BuiltinClassLoader bootLoader() {
88 return BOOT_LOADER;
89 }
90
91 /**
92 * Returns the platform class loader.
93 */
94 public static ClassLoader platformClassLoader() {
95 return PLATFORM_LOADER;
96 }
97
98 /**
99 * Returns the application class loader.
100 */
101 public static ClassLoader appClassLoader() {
102 return APP_LOADER;
103 }
104
105 /**
106 * The class loader that is used to find resources in modules defined to
107 * the boot class loader. It is not used for class loading.
108 */
109 private static class BootClassLoader extends BuiltinClassLoader {
110 BootClassLoader(URLClassPath bcp) {
111 super(null, null, bcp);
112 }
113
114 @Override
115 protected Class<?> loadClassOrNull(String cn) {
116 return JLA.findBootstrapClassOrNull(this, cn);
117 }
118 };
119
120 /**
121 * The platform class loader, a unique type to make it easier to distinguish
122 * from the application class loader.
123 */
124 private static class PlatformClassLoader extends BuiltinClassLoader {
125 static {
126 if (!ClassLoader.registerAsParallelCapable())
127 throw new InternalError();
128 }
129
130 PlatformClassLoader(BootClassLoader parent) {
131 super("platform", parent, null);
132 }
133
134 /**
135 * Called by the VM to support define package for AppCDS.
136 *
137 * Shared classes are returned in ClassLoader::findLoadedClass
138 * that bypass the defineClass call.
139 */
140 private Package definePackage(String pn, Module module) {
141 return JLA.definePackage(this, pn, module);
142 }
143 }
144
145 /**
146 * The application class loader that is a {@code BuiltinClassLoader} with
147 * customizations to be compatible with long standing behavior.
148 */
149 private static class AppClassLoader extends BuiltinClassLoader {
150 static {
151 if (!ClassLoader.registerAsParallelCapable())
152 throw new InternalError();
153 }
154
155 final URLClassPath ucp;
156
157 AppClassLoader(PlatformClassLoader parent, URLClassPath ucp) {
158 super("app", parent, ucp);
159 this.ucp = ucp;
160 }
161
162 @Override
163 protected Class<?> loadClass(String cn, boolean resolve)
164 throws ClassNotFoundException
165 {
166 // for compatibility reasons, say where restricted package list has
167 // been updated to list API packages in the unnamed module.
168 SecurityManager sm = System.getSecurityManager();
169 if (sm != null) {
170 int i = cn.lastIndexOf('.');
171 if (i != -1) {
172 sm.checkPackageAccess(cn.substring(0, i));
173 }
174 }
175
176 return super.loadClass(cn, resolve);
177 }
178
179 @Override
180 protected PermissionCollection getPermissions(CodeSource cs) {
181 PermissionCollection perms = super.getPermissions(cs);
182 perms.add(new RuntimePermission("exitVM"));
183 return perms;
184 }
185
186 /**
187 * Called by the VM to support dynamic additions to the class path
188 *
189 * @see java.lang.instrument.Instrumentation#appendToSystemClassLoaderSearch
190 */
191 void appendToClassPathForInstrumentation(String path) {
192 ucp.addFile(path);
193 }
194
195 /**
196 * Called by the VM to support define package for AppCDS
197 *
198 * Shared classes are returned in ClassLoader::findLoadedClass
199 * that bypass the defineClass call.
200 */
201 private Package definePackage(String pn, Module module) {
202 return JLA.definePackage(this, pn, module);
203 }
204
205 /**
206 * Called by the VM to support define package for AppCDS
207 */
208 protected Package defineOrCheckPackage(String pn, Manifest man, URL url) {
209 return super.defineOrCheckPackage(pn, man, url);
210 }
211 }
212
213 /**
214 * Attempts to convert the given string to a file URL.
215 *
216 * @apiNote This is called by the VM
217 */
218 @Deprecated
219 private static URL toFileURL(String s) {
220 try {
221 // Use an intermediate File object to construct a URI/URL without
222 // authority component as URLClassPath can't handle URLs with a UNC
223 // server name in the authority component.
224 return Paths.get(s).toRealPath().toFile().toURI().toURL();
225 } catch (InvalidPathException | IOException ignore) {
226 // malformed path string or class path element does not exist
227 return null;
228 }
229 }
230 }