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.loader;
27
28 import java.io.File;
29 import java.io.IOException;
30 import java.lang.reflect.Module;
31 import java.net.URL;
32 import java.nio.file.InvalidPathException;
33 import java.nio.file.Paths;
34 import java.security.CodeSource;
35 import java.security.PermissionCollection;
36 import java.util.jar.Manifest;
37
38 import jdk.internal.misc.JavaLangAccess;
39 import jdk.internal.misc.SharedSecrets;
40 import jdk.internal.misc.VM;
41
42
43 /**
44 * Creates and provides access to the built-in platform and application class
45 * loaders. It also creates the class loader that is used to locate resources
46 * in modules defined to the boot class loader.
47 */
48
49 public class ClassLoaders {
50
51 private ClassLoaders() { }
52
53 private static final JavaLangAccess JLA = SharedSecrets.getJavaLangAccess();
54
55 // the built-in class loaders
56 private static final BootClassLoader BOOT_LOADER;
57 private static final PlatformClassLoader PLATFORM_LOADER;
58 private static final AppClassLoader APP_LOADER;
59
60 /**
61 * Creates the built-in class loaders
62 */
63 static {
64
65 // -Xbootclasspth/a or -javaagent Boot-Class-Path
66 URLClassPath bcp = null;
67 String s = VM.getSavedProperty("jdk.boot.class.path.append");
68 if (s != null && s.length() > 0)
69 bcp = toURLClassPath(s);
70
71 // we have a class path if -cp is specified or -m is not specified.
72 // If neither is specified then default to -cp <working directory>.
73 URLClassPath ucp = null;
74 String mainMid = System.getProperty("jdk.module.main");
75 String cp = System.getProperty("java.class.path");
76 if (mainMid == null && cp == null)
77 cp = "";
78 if (cp != null)
79 ucp = toURLClassPath(cp);
80
81
82 // create the class loaders
83 BOOT_LOADER = new BootClassLoader(bcp);
84 PLATFORM_LOADER = new PlatformClassLoader(BOOT_LOADER);
85 APP_LOADER = new AppClassLoader(PLATFORM_LOADER, ucp);
86 }
87
88 /**
89 * Returns the class loader that is used to find resources in modules
90 * defined to the boot class loader.
91 *
92 * @apiNote This method is not public, it should instead be used via
93 * the BootLoader class that provides a restricted API to this class
94 * loader.
95 */
96 static BuiltinClassLoader bootLoader() {
97 return BOOT_LOADER;
98 }
99
100 /**
101 * Returns the platform class loader.
102 */
103 public static ClassLoader platformClassLoader() {
104 return PLATFORM_LOADER;
105 }
106
107 /**
108 * Returns the application class loader.
109 */
110 public static ClassLoader appClassLoader() {
111 return APP_LOADER;
112 }
113
114 /**
115 * The class loader that is used to find resources in modules defined to
116 * the boot class loader. It is not used for class loading.
117 */
118 private static class BootClassLoader extends BuiltinClassLoader {
119 BootClassLoader(URLClassPath bcp) {
120 super(null, bcp);
121 }
122
123 @Override
124 protected Class<?> loadClassOrNull(String cn) {
125 return JLA.findBootstrapClassOrNull(this, cn);
126 }
127 };
128
129 /**
130 * The platform class loader, a unique type to make it easier to distinguish
131 * from the application class loader.
132 */
133 private static class PlatformClassLoader extends BuiltinClassLoader {
134 static {
135 if (!ClassLoader.registerAsParallelCapable())
136 throw new InternalError();
137 }
138
139 PlatformClassLoader(BootClassLoader parent) {
140 super(parent, null);
141 }
142
143 /**
144 * Called by the VM to support define package for AppCDS.
145 *
146 * Shared classes are returned in ClassLoader::findLoadedClass
147 * that bypass the defineClass call.
148 */
149 private Package definePackage(String pn, Module module) {
150 return JLA.definePackage(this, pn, module);
151 }
152 }
153
154 /**
155 * The application class loader that is a {@code BuiltinClassLoader} with
156 * customizations to be compatible with long standing behavior.
157 */
158 private static class AppClassLoader extends BuiltinClassLoader {
159 static {
160 if (!ClassLoader.registerAsParallelCapable())
161 throw new InternalError();
162 }
163
164 final URLClassPath ucp;
165
166 AppClassLoader(PlatformClassLoader parent, URLClassPath ucp) {
167 super(parent, ucp);
168 this.ucp = ucp;
169 }
170
171 @Override
172 protected Class<?> loadClass(String cn, boolean resolve)
173 throws ClassNotFoundException
174 {
175 // for compatibility reasons, say where restricted package list has
176 // been updated to list API packages in the unnamed module.
177 SecurityManager sm = System.getSecurityManager();
178 if (sm != null) {
179 int i = cn.lastIndexOf('.');
180 if (i != -1) {
181 sm.checkPackageAccess(cn.substring(0, i));
182 }
183 }
184
185 return super.loadClass(cn, resolve);
186 }
187
188 @Override
189 protected PermissionCollection getPermissions(CodeSource cs) {
190 PermissionCollection perms = super.getPermissions(cs);
191 perms.add(new RuntimePermission("exitVM"));
192 return perms;
193 }
194
195 /**
196 * Called by the VM to support dynamic additions to the class path
197 *
198 * @see java.lang.instrument.Instrumentation#appendToSystemClassLoaderSearch
199 */
200 void appendToClassPathForInstrumentation(String path) {
201 addClassPathToUCP(path, ucp);
202 }
203
204 /**
205 * Called by the VM to support define package for AppCDS
206 *
207 * Shared classes are returned in ClassLoader::findLoadedClass
208 * that bypass the defineClass call.
209 */
210 private Package definePackage(String pn, Module module) {
211 return JLA.definePackage(this, pn, module);
212 }
213
214 /**
215 * Called by the VM to support define package for AppCDS
216 */
217 protected Package defineOrCheckPackage(String pn, Manifest man, URL url) {
218 return super.defineOrCheckPackage(pn, man, url);
219 }
220 }
221
222 /**
223 * Returns a {@code URLClassPath} of file URLs to each of the elements in
224 * the given class path.
225 */
226 private static URLClassPath toURLClassPath(String cp) {
227 URLClassPath ucp = new URLClassPath(new URL[0]);
228 addClassPathToUCP(cp, ucp);
229 return ucp;
230 }
231
232 /**
233 * Converts the elements in the given class path to file URLs and adds
234 * them to the given URLClassPath.
235 */
236 private static void addClassPathToUCP(String cp, URLClassPath ucp) {
237 int off = 0;
238 int next;
239 while ((next = cp.indexOf(File.pathSeparator, off)) != -1) {
240 URL url = toFileURL(cp.substring(off, next));
241 if (url != null)
242 ucp.addURL(url);
243 off = next + 1;
244 }
245
246 // remaining
247 URL url = toFileURL(cp.substring(off));
248 if (url != null)
249 ucp.addURL(url);
250 }
251
252 /**
253 * Attempts to convert the given string to a file URL.
254 *
255 * @apiNote This is called by the VM
256 */
257 private static URL toFileURL(String s) {
258 try {
259 return Paths.get(s).toRealPath().toUri().toURL();
260 } catch (InvalidPathException | IOException ignore) {
261 // malformed path string or class path element does not exist
262 return null;
263 }
264 }
265
266 }