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| 1 | +/* | |
| 2 | + * Copyright (c) 1999, 2010, 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 java.lang.reflect; | |
| 27 | + | |
| 28 | +import java.lang.ref.Reference; | |
| 29 | +import java.lang.ref.WeakReference; | |
| 30 | +import java.util.Arrays; | |
| 31 | +import java.util.Collections; | |
| 32 | +import java.util.HashMap; | |
| 33 | +import java.util.HashSet; | |
| 34 | +import java.util.Map; | |
| 35 | +import java.util.Set; | |
| 36 | +import java.util.List; | |
| 37 | +import java.util.WeakHashMap; | |
| 38 | +import sun.misc.ProxyGenerator; | |
| 39 | + | |
| 40 | +/** | |
| 41 | + * {@code Proxy} provides static methods for creating dynamic proxy | |
| 42 | + * classes and instances, and it is also the superclass of all | |
| 43 | + * dynamic proxy classes created by those methods. | |
| 44 | + * | |
| 45 | + * <p>To create a proxy for some interface {@code Foo}: | |
| 46 | + * <pre> | |
| 47 | + * InvocationHandler handler = new MyInvocationHandler(...); | |
| 48 | + * Class proxyClass = Proxy.getProxyClass( | |
| 49 | + * Foo.class.getClassLoader(), new Class[] { Foo.class }); | |
| 50 | + * Foo f = (Foo) proxyClass. | |
| 51 | + * getConstructor(new Class[] { InvocationHandler.class }). | |
| 52 | + * newInstance(new Object[] { handler }); | |
| 53 | + * </pre> | |
| 54 | + * or more simply: | |
| 55 | + * <pre> | |
| 56 | + * Foo f = (Foo) Proxy.newProxyInstance(Foo.class.getClassLoader(), | |
| 57 | + * new Class[] { Foo.class }, | |
| 58 | + * handler); | |
| 59 | + * </pre> | |
| 60 | + * | |
| 61 | + * <p>A <i>dynamic proxy class</i> (simply referred to as a <i>proxy | |
| 62 | + * class</i> below) is a class that implements a list of interfaces | |
| 63 | + * specified at runtime when the class is created, with behavior as | |
| 64 | + * described below. | |
| 65 | + * | |
| 66 | + * A <i>proxy interface</i> is such an interface that is implemented | |
| 67 | + * by a proxy class. | |
| 68 | + * | |
| 69 | + * A <i>proxy instance</i> is an instance of a proxy class. | |
| 70 | + * | |
| 71 | + * Each proxy instance has an associated <i>invocation handler</i> | |
| 72 | + * object, which implements the interface {@link InvocationHandler}. | |
| 73 | + * A method invocation on a proxy instance through one of its proxy | |
| 74 | + * interfaces will be dispatched to the {@link InvocationHandler#invoke | |
| 75 | + * invoke} method of the instance's invocation handler, passing the proxy | |
| 76 | + * instance, a {@code java.lang.reflect.Method} object identifying | |
| 77 | + * the method that was invoked, and an array of type {@code Object} | |
| 78 | + * containing the arguments. The invocation handler processes the | |
| 79 | + * encoded method invocation as appropriate and the result that it | |
| 80 | + * returns will be returned as the result of the method invocation on | |
| 81 | + * the proxy instance. | |
| 82 | + * | |
| 83 | + * <p>A proxy class has the following properties: | |
| 84 | + * | |
| 85 | + * <ul> | |
| 86 | + * <li>Proxy classes are public, final, and not abstract. | |
| 87 | + * | |
| 88 | + * <li>The unqualified name of a proxy class is unspecified. The space | |
| 89 | + * of class names that begin with the string {@code "$Proxy"} | |
| 90 | + * should be, however, reserved for proxy classes. | |
| 91 | + * | |
| 92 | + * <li>A proxy class extends {@code java.lang.reflect.Proxy}. | |
| 93 | + * | |
| 94 | + * <li>A proxy class implements exactly the interfaces specified at its | |
| 95 | + * creation, in the same order. | |
| 96 | + * | |
| 97 | + * <li>If a proxy class implements a non-public interface, then it will | |
| 98 | + * be defined in the same package as that interface. Otherwise, the | |
| 99 | + * package of a proxy class is also unspecified. Note that package | |
| 100 | + * sealing will not prevent a proxy class from being successfully defined | |
| 101 | + * in a particular package at runtime, and neither will classes already | |
| 102 | + * defined by the same class loader and the same package with particular | |
| 103 | + * signers. | |
| 104 | + * | |
| 105 | + * <li>Since a proxy class implements all of the interfaces specified at | |
| 106 | + * its creation, invoking {@code getInterfaces} on its | |
| 107 | + * {@code Class} object will return an array containing the same | |
| 108 | + * list of interfaces (in the order specified at its creation), invoking | |
| 109 | + * {@code getMethods} on its {@code Class} object will return | |
| 110 | + * an array of {@code Method} objects that include all of the | |
| 111 | + * methods in those interfaces, and invoking {@code getMethod} will | |
| 112 | + * find methods in the proxy interfaces as would be expected. | |
| 113 | + * | |
| 114 | + * <li>The {@link Proxy#isProxyClass Proxy.isProxyClass} method will | |
| 115 | + * return true if it is passed a proxy class-- a class returned by | |
| 116 | + * {@code Proxy.getProxyClass} or the class of an object returned by | |
| 117 | + * {@code Proxy.newProxyInstance}-- and false otherwise. | |
| 118 | + * | |
| 119 | + * <li>The {@code java.security.ProtectionDomain} of a proxy class | |
| 120 | + * is the same as that of system classes loaded by the bootstrap class | |
| 121 | + * loader, such as {@code java.lang.Object}, because the code for a | |
| 122 | + * proxy class is generated by trusted system code. This protection | |
| 123 | + * domain will typically be granted | |
| 124 | + * {@code java.security.AllPermission}. | |
| 125 | + * | |
| 126 | + * <li>Each proxy class has one public constructor that takes one argument, | |
| 127 | + * an implementation of the interface {@link InvocationHandler}, to set | |
| 128 | + * the invocation handler for a proxy instance. Rather than having to use | |
| 129 | + * the reflection API to access the public constructor, a proxy instance | |
| 130 | + * can be also be created by calling the {@link Proxy#newProxyInstance | |
| 131 | + * Proxy.newProxyInstance} method, which combines the actions of calling | |
| 132 | + * {@link Proxy#getProxyClass Proxy.getProxyClass} with invoking the | |
| 133 | + * constructor with an invocation handler. | |
| 134 | + * </ul> | |
| 135 | + * | |
| 136 | + * <p>A proxy instance has the following properties: | |
| 137 | + * | |
| 138 | + * <ul> | |
| 139 | + * <li>Given a proxy instance {@code proxy} and one of the | |
| 140 | + * interfaces implemented by its proxy class {@code Foo}, the | |
| 141 | + * following expression will return true: | |
| 142 | + * <pre> | |
| 143 | + * {@code proxy instanceof Foo} | |
| 144 | + * </pre> | |
| 145 | + * and the following cast operation will succeed (rather than throwing | |
| 146 | + * a {@code ClassCastException}): | |
| 147 | + * <pre> | |
| 148 | + * {@code (Foo) proxy} | |
| 149 | + * </pre> | |
| 150 | + * | |
| 151 | + * <li>Each proxy instance has an associated invocation handler, the one | |
| 152 | + * that was passed to its constructor. The static | |
| 153 | + * {@link Proxy#getInvocationHandler Proxy.getInvocationHandler} method | |
| 154 | + * will return the invocation handler associated with the proxy instance | |
| 155 | + * passed as its argument. | |
| 156 | + * | |
| 157 | + * <li>An interface method invocation on a proxy instance will be | |
| 158 | + * encoded and dispatched to the invocation handler's {@link | |
| 159 | + * InvocationHandler#invoke invoke} method as described in the | |
| 160 | + * documentation for that method. | |
| 161 | + * | |
| 162 | + * <li>An invocation of the {@code hashCode}, | |
| 163 | + * {@code equals}, or {@code toString} methods declared in | |
| 164 | + * {@code java.lang.Object} on a proxy instance will be encoded and | |
| 165 | + * dispatched to the invocation handler's {@code invoke} method in | |
| 166 | + * the same manner as interface method invocations are encoded and | |
| 167 | + * dispatched, as described above. The declaring class of the | |
| 168 | + * {@code Method} object passed to {@code invoke} will be | |
| 169 | + * {@code java.lang.Object}. Other public methods of a proxy | |
| 170 | + * instance inherited from {@code java.lang.Object} are not | |
| 171 | + * overridden by a proxy class, so invocations of those methods behave | |
| 172 | + * like they do for instances of {@code java.lang.Object}. | |
| 173 | + * </ul> | |
| 174 | + * | |
| 175 | + * <h3>Methods Duplicated in Multiple Proxy Interfaces</h3> | |
| 176 | + * | |
| 177 | + * <p>When two or more interfaces of a proxy class contain a method with | |
| 178 | + * the same name and parameter signature, the order of the proxy class's | |
| 179 | + * interfaces becomes significant. When such a <i>duplicate method</i> | |
| 180 | + * is invoked on a proxy instance, the {@code Method} object passed | |
| 181 | + * to the invocation handler will not necessarily be the one whose | |
| 182 | + * declaring class is assignable from the reference type of the interface | |
| 183 | + * that the proxy's method was invoked through. This limitation exists | |
| 184 | + * because the corresponding method implementation in the generated proxy | |
| 185 | + * class cannot determine which interface it was invoked through. | |
| 186 | + * Therefore, when a duplicate method is invoked on a proxy instance, | |
| 187 | + * the {@code Method} object for the method in the foremost interface | |
| 188 | + * that contains the method (either directly or inherited through a | |
| 189 | + * superinterface) in the proxy class's list of interfaces is passed to | |
| 190 | + * the invocation handler's {@code invoke} method, regardless of the | |
| 191 | + * reference type through which the method invocation occurred. | |
| 192 | + * | |
| 193 | + * <p>If a proxy interface contains a method with the same name and | |
| 194 | + * parameter signature as the {@code hashCode}, {@code equals}, | |
| 195 | + * or {@code toString} methods of {@code java.lang.Object}, | |
| 196 | + * when such a method is invoked on a proxy instance, the | |
| 197 | + * {@code Method} object passed to the invocation handler will have | |
| 198 | + * {@code java.lang.Object} as its declaring class. In other words, | |
| 199 | + * the public, non-final methods of {@code java.lang.Object} | |
| 200 | + * logically precede all of the proxy interfaces for the determination of | |
| 201 | + * which {@code Method} object to pass to the invocation handler. | |
| 202 | + * | |
| 203 | + * <p>Note also that when a duplicate method is dispatched to an | |
| 204 | + * invocation handler, the {@code invoke} method may only throw | |
| 205 | + * checked exception types that are assignable to one of the exception | |
| 206 | + * types in the {@code throws} clause of the method in <i>all</i> of | |
| 207 | + * the proxy interfaces that it can be invoked through. If the | |
| 208 | + * {@code invoke} method throws a checked exception that is not | |
| 209 | + * assignable to any of the exception types declared by the method in one | |
| 210 | + * of the proxy interfaces that it can be invoked through, then an | |
| 211 | + * unchecked {@code UndeclaredThrowableException} will be thrown by | |
| 212 | + * the invocation on the proxy instance. This restriction means that not | |
| 213 | + * all of the exception types returned by invoking | |
| 214 | + * {@code getExceptionTypes} on the {@code Method} object | |
| 215 | + * passed to the {@code invoke} method can necessarily be thrown | |
| 216 | + * successfully by the {@code invoke} method. | |
| 217 | + * | |
| 218 | + * @author Peter Jones | |
| 219 | + * @see InvocationHandler | |
| 220 | + * @since 1.3 | |
| 221 | + */ | |
| 222 | +public class Proxy implements java.io.Serializable { | |
| 223 | + | |
| 224 | + private static final long serialVersionUID = -2222568056686623797L; | |
| 225 | + | |
| 226 | + /** prefix for all proxy class names */ | |
| 227 | + private final static String proxyClassNamePrefix = "$Proxy"; | |
| 228 | + | |
| 229 | + /** parameter types of a proxy class constructor */ | |
| 230 | + private final static Class[] constructorParams = | |
| 231 | + { InvocationHandler.class }; | |
| 232 | + | |
| 233 | + /** maps a class loader to the proxy class cache for that loader */ | |
| 234 | + private static Map<ClassLoader, Map<List<String>, Object>> loaderToCache | |
| 235 | + = new WeakHashMap<>(); | |
| 236 | + | |
| 237 | + /** marks that a particular proxy class is currently being generated */ | |
| 238 | + private static Object pendingGenerationMarker = new Object(); | |
| 239 | + | |
| 240 | + /** next number to use for generation of unique proxy class names */ | |
| 241 | + private static long nextUniqueNumber = 0; | |
| 242 | + private static Object nextUniqueNumberLock = new Object(); | |
| 243 | + | |
| 244 | + /** set of all generated proxy classes, for isProxyClass implementation */ | |
| 245 | + private static Map<Class<?>, Void> proxyClasses = | |
| 246 | + Collections.synchronizedMap(new WeakHashMap<Class<?>, Void>()); | |
| 247 | + | |
| 248 | + /** | |
| 249 | + * the invocation handler for this proxy instance. | |
| 250 | + * @serial | |
| 251 | + */ | |
| 252 | + protected InvocationHandler h; | |
| 253 | + | |
| 254 | + /** | |
| 255 | + * Prohibits instantiation. | |
| 256 | + */ | |
| 257 | + private Proxy() { | |
| 258 | + } | |
| 259 | + | |
| 260 | + /** | |
| 261 | + * Constructs a new {@code Proxy} instance from a subclass | |
| 262 | + * (typically, a dynamic proxy class) with the specified value | |
| 263 | + * for its invocation handler. | |
| 264 | + * | |
| 265 | + * @param h the invocation handler for this proxy instance | |
| 266 | + */ | |
| 267 | + protected Proxy(InvocationHandler h) { | |
| 268 | + this.h = h; | |
| 269 | + } | |
| 270 | + | |
| 271 | + /** | |
| 272 | + * Returns the {@code java.lang.Class} object for a proxy class | |
| 273 | + * given a class loader and an array of interfaces. The proxy class | |
| 274 | + * will be defined by the specified class loader and will implement | |
| 275 | + * all of the supplied interfaces. If a proxy class for the same | |
| 276 | + * permutation of interfaces has already been defined by the class | |
| 277 | + * loader, then the existing proxy class will be returned; otherwise, | |
| 278 | + * a proxy class for those interfaces will be generated dynamically | |
| 279 | + * and defined by the class loader. | |
| 280 | + * | |
| 281 | + * <p>There are several restrictions on the parameters that may be | |
| 282 | + * passed to {@code Proxy.getProxyClass}: | |
| 283 | + * | |
| 284 | + * <ul> | |
| 285 | + * <li>All of the {@code Class} objects in the | |
| 286 | + * {@code interfaces} array must represent interfaces, not | |
| 287 | + * classes or primitive types. | |
| 288 | + * | |
| 289 | + * <li>No two elements in the {@code interfaces} array may | |
| 290 | + * refer to identical {@code Class} objects. | |
| 291 | + * | |
| 292 | + * <li>All of the interface types must be visible by name through the | |
| 293 | + * specified class loader. In other words, for class loader | |
| 294 | + * {@code cl} and every interface {@code i}, the following | |
| 295 | + * expression must be true: | |
| 296 | + * <pre> | |
| 297 | + * Class.forName(i.getName(), false, cl) == i | |
| 298 | + * </pre> | |
| 299 | + * | |
| 300 | + * <li>All non-public interfaces must be in the same package; | |
| 301 | + * otherwise, it would not be possible for the proxy class to | |
| 302 | + * implement all of the interfaces, regardless of what package it is | |
| 303 | + * defined in. | |
| 304 | + * | |
| 305 | + * <li>For any set of member methods of the specified interfaces | |
| 306 | + * that have the same signature: | |
| 307 | + * <ul> | |
| 308 | + * <li>If the return type of any of the methods is a primitive | |
| 309 | + * type or void, then all of the methods must have that same | |
| 310 | + * return type. | |
| 311 | + * <li>Otherwise, one of the methods must have a return type that | |
| 312 | + * is assignable to all of the return types of the rest of the | |
| 313 | + * methods. | |
| 314 | + * </ul> | |
| 315 | + * | |
| 316 | + * <li>The resulting proxy class must not exceed any limits imposed | |
| 317 | + * on classes by the virtual machine. For example, the VM may limit | |
| 318 | + * the number of interfaces that a class may implement to 65535; in | |
| 319 | + * that case, the size of the {@code interfaces} array must not | |
| 320 | + * exceed 65535. | |
| 321 | + * </ul> | |
| 322 | + * | |
| 323 | + * <p>If any of these restrictions are violated, | |
| 324 | + * {@code Proxy.getProxyClass} will throw an | |
| 325 | + * {@code IllegalArgumentException}. If the {@code interfaces} | |
| 326 | + * array argument or any of its elements are {@code null}, a | |
| 327 | + * {@code NullPointerException} will be thrown. | |
| 328 | + * | |
| 329 | + * <p>Note that the order of the specified proxy interfaces is | |
| 330 | + * significant: two requests for a proxy class with the same combination | |
| 331 | + * of interfaces but in a different order will result in two distinct | |
| 332 | + * proxy classes. | |
| 333 | + * | |
| 334 | + * @param loader the class loader to define the proxy class | |
| 335 | + * @param interfaces the list of interfaces for the proxy class | |
| 336 | + * to implement | |
| 337 | + * @return a proxy class that is defined in the specified class loader | |
| 338 | + * and that implements the specified interfaces | |
| 339 | + * @throws IllegalArgumentException if any of the restrictions on the | |
| 340 | + * parameters that may be passed to {@code getProxyClass} | |
| 341 | + * are violated | |
| 342 | + * @throws NullPointerException if the {@code interfaces} array | |
| 343 | + * argument or any of its elements are {@code null} | |
| 344 | + */ | |
| 345 | + public static Class<?> getProxyClass(ClassLoader loader, | |
| 346 | + Class<?>... interfaces) | |
| 347 | + throws IllegalArgumentException | |
| 348 | + { | |
| 349 | + if (interfaces.length > 65535) { | |
| 350 | + throw new IllegalArgumentException("interface limit exceeded"); | |
| 351 | + } | |
| 352 | + | |
| 353 | + Class<?> proxyClass = null; | |
| 354 | + | |
| 355 | + /* collect interface names to use as key for proxy class cache */ | |
| 356 | + String[] interfaceNames = new String[interfaces.length]; | |
| 357 | + | |
| 358 | + // for detecting duplicates | |
| 359 | + Set<Class<?>> interfaceSet = new HashSet<>(); | |
| 360 | + | |
| 361 | + for (int i = 0; i < interfaces.length; i++) { | |
| 362 | + /* | |
| 363 | + * Verify that the class loader resolves the name of this | |
| 364 | + * interface to the same Class object. | |
| 365 | + */ | |
| 366 | + String interfaceName = interfaces[i].getName(); | |
| 367 | + Class<?> interfaceClass = null; | |
| 368 | + try { | |
| 369 | + interfaceClass = Class.forName(interfaceName, false, loader); | |
| 370 | + } catch (ClassNotFoundException e) { | |
| 371 | + } | |
| 372 | + if (interfaceClass != interfaces[i]) { | |
| 373 | + throw new IllegalArgumentException( | |
| 374 | + interfaces[i] + " is not visible from class loader"); | |
| 375 | + } | |
| 376 | + | |
| 377 | + /* | |
| 378 | + * Verify that the Class object actually represents an | |
| 379 | + * interface. | |
| 380 | + */ | |
| 381 | + if (!interfaceClass.isInterface()) { | |
| 382 | + throw new IllegalArgumentException( | |
| 383 | + interfaceClass.getName() + " is not an interface"); | |
| 384 | + } | |
| 385 | + | |
| 386 | + /* | |
| 387 | + * Verify that this interface is not a duplicate. | |
| 388 | + */ | |
| 389 | + if (interfaceSet.contains(interfaceClass)) { | |
| 390 | + throw new IllegalArgumentException( | |
| 391 | + "repeated interface: " + interfaceClass.getName()); | |
| 392 | + } | |
| 393 | + interfaceSet.add(interfaceClass); | |
| 394 | + | |
| 395 | + interfaceNames[i] = interfaceName; | |
| 396 | + } | |
| 397 | + | |
| 398 | + /* | |
| 399 | + * Using string representations of the proxy interfaces as | |
| 400 | + * keys in the proxy class cache (instead of their Class | |
| 401 | + * objects) is sufficient because we require the proxy | |
| 402 | + * interfaces to be resolvable by name through the supplied | |
| 403 | + * class loader, and it has the advantage that using a string | |
| 404 | + * representation of a class makes for an implicit weak | |
| 405 | + * reference to the class. | |
| 406 | + */ | |
| 407 | + List<String> key = Arrays.asList(interfaceNames); | |
| 408 | + | |
| 409 | + /* | |
| 410 | + * Find or create the proxy class cache for the class loader. | |
| 411 | + */ | |
| 412 | + Map<List<String>, Object> cache; | |
| 413 | + synchronized (loaderToCache) { | |
| 414 | + cache = loaderToCache.get(loader); | |
| 415 | + if (cache == null) { | |
| 416 | + cache = new HashMap<>(); | |
| 417 | + loaderToCache.put(loader, cache); | |
| 418 | + } | |
| 419 | + /* | |
| 420 | + * This mapping will remain valid for the duration of this | |
| 421 | + * method, without further synchronization, because the mapping | |
| 422 | + * will only be removed if the class loader becomes unreachable. | |
| 423 | + */ | |
| 424 | + } | |
| 425 | + | |
| 426 | + /* | |
| 427 | + * Look up the list of interfaces in the proxy class cache using | |
| 428 | + * the key. This lookup will result in one of three possible | |
| 429 | + * kinds of values: | |
| 430 | + * null, if there is currently no proxy class for the list of | |
| 431 | + * interfaces in the class loader, | |
| 432 | + * the pendingGenerationMarker object, if a proxy class for the | |
| 433 | + * list of interfaces is currently being generated, | |
| 434 | + * or a weak reference to a Class object, if a proxy class for | |
| 435 | + * the list of interfaces has already been generated. | |
| 436 | + */ | |
| 437 | + synchronized (cache) { | |
| 438 | + /* | |
| 439 | + * Note that we need not worry about reaping the cache for | |
| 440 | + * entries with cleared weak references because if a proxy class | |
| 441 | + * has been garbage collected, its class loader will have been | |
| 442 | + * garbage collected as well, so the entire cache will be reaped | |
| 443 | + * from the loaderToCache map. | |
| 444 | + */ | |
| 445 | + do { | |
| 446 | + Object value = cache.get(key); | |
| 447 | + if (value instanceof Reference) { | |
| 448 | + proxyClass = (Class<?>) ((Reference) value).get(); | |
| 449 | + } | |
| 450 | + if (proxyClass != null) { | |
| 451 | + // proxy class already generated: return it | |
| 452 | + return proxyClass; | |
| 453 | + } else if (value == pendingGenerationMarker) { | |
| 454 | + // proxy class being generated: wait for it | |
| 455 | + try { | |
| 456 | + cache.wait(); | |
| 457 | + } catch (InterruptedException e) { | |
| 458 | + /* | |
| 459 | + * The class generation that we are waiting for should | |
| 460 | + * take a small, bounded time, so we can safely ignore | |
| 461 | + * thread interrupts here. | |
| 462 | + */ | |
| 463 | + } | |
| 464 | + continue; | |
| 465 | + } else { | |
| 466 | + /* | |
| 467 | + * No proxy class for this list of interfaces has been | |
| 468 | + * generated or is being generated, so we will go and | |
| 469 | + * generate it now. Mark it as pending generation. | |
| 470 | + */ | |
| 471 | + cache.put(key, pendingGenerationMarker); | |
| 472 | + break; | |
| 473 | + } | |
| 474 | + } while (true); | |
| 475 | + } | |
| 476 | + | |
| 477 | + try { | |
| 478 | + String proxyPkg = null; // package to define proxy class in | |
| 479 | + | |
| 480 | + /* | |
| 481 | + * Record the package of a non-public proxy interface so that the | |
| 482 | + * proxy class will be defined in the same package. Verify that | |
| 483 | + * all non-public proxy interfaces are in the same package. | |
| 484 | + */ | |
| 485 | + for (int i = 0; i < interfaces.length; i++) { | |
| 486 | + int flags = interfaces[i].getModifiers(); | |
| 487 | + if (!Modifier.isPublic(flags)) { | |
| 488 | + String name = interfaces[i].getName(); | |
| 489 | + int n = name.lastIndexOf('.'); | |
| 490 | + String pkg = ((n == -1) ? "" : name.substring(0, n + 1)); | |
| 491 | + if (proxyPkg == null) { | |
| 492 | + proxyPkg = pkg; | |
| 493 | + } else if (!pkg.equals(proxyPkg)) { | |
| 494 | + throw new IllegalArgumentException( | |
| 495 | + "non-public interfaces from different packages"); | |
| 496 | + } | |
| 497 | + } | |
| 498 | + } | |
| 499 | + | |
| 500 | + if (proxyPkg == null) { // if no non-public proxy interfaces, | |
| 501 | + proxyPkg = ""; // use the unnamed package | |
| 502 | + } | |
| 503 | + | |
| 504 | + { | |
| 505 | + /* | |
| 506 | + * Choose a name for the proxy class to generate. | |
| 507 | + */ | |
| 508 | + long num; | |
| 509 | + synchronized (nextUniqueNumberLock) { | |
| 510 | + num = nextUniqueNumber++; | |
| 511 | + } | |
| 512 | + String proxyName = proxyPkg + proxyClassNamePrefix + num; | |
| 513 | + /* | |
| 514 | + * Verify that the class loader hasn't already | |
| 515 | + * defined a class with the chosen name. | |
| 516 | + */ | |
| 517 | + | |
| 518 | + /* | |
| 519 | + * Generate the specified proxy class. | |
| 520 | + */ | |
| 521 | + byte[] proxyClassFile = ProxyGenerator.generateProxyClass( | |
| 522 | + proxyName, interfaces); | |
| 523 | + try { | |
| 524 | + proxyClass = defineClass0(loader, proxyName, | |
| 525 | + proxyClassFile, 0, proxyClassFile.length); | |
| 526 | + } catch (ClassFormatError e) { | |
| 527 | + /* | |
| 528 | + * A ClassFormatError here means that (barring bugs in the | |
| 529 | + * proxy class generation code) there was some other | |
| 530 | + * invalid aspect of the arguments supplied to the proxy | |
| 531 | + * class creation (such as virtual machine limitations | |
| 532 | + * exceeded). | |
| 533 | + */ | |
| 534 | + throw new IllegalArgumentException(e.toString()); | |
| 535 | + } | |
| 536 | + } | |
| 537 | + // add to set of all generated proxy classes, for isProxyClass | |
| 538 | + proxyClasses.put(proxyClass, null); | |
| 539 | + | |
| 540 | + } finally { | |
| 541 | + /* | |
| 542 | + * We must clean up the "pending generation" state of the proxy | |
| 543 | + * class cache entry somehow. If a proxy class was successfully | |
| 544 | + * generated, store it in the cache (with a weak reference); | |
| 545 | + * otherwise, remove the reserved entry. In all cases, notify | |
| 546 | + * all waiters on reserved entries in this cache. | |
| 547 | + */ | |
| 548 | + synchronized (cache) { | |
| 549 | + if (proxyClass != null) { | |
| 550 | + cache.put(key, new WeakReference<Class<?>>(proxyClass)); | |
| 551 | + } else { | |
| 552 | + cache.remove(key); | |
| 553 | + } | |
| 554 | + cache.notifyAll(); | |
| 555 | + } | |
| 556 | + } | |
| 557 | + return proxyClass; | |
| 558 | + } | |
| 559 | + | |
| 560 | + /** | |
| 561 | + * Returns an instance of a proxy class for the specified interfaces | |
| 562 | + * that dispatches method invocations to the specified invocation | |
| 563 | + * handler. This method is equivalent to: | |
| 564 | + * <pre> | |
| 565 | + * Proxy.getProxyClass(loader, interfaces). | |
| 566 | + * getConstructor(new Class[] { InvocationHandler.class }). | |
| 567 | + * newInstance(new Object[] { handler }); | |
| 568 | + * </pre> | |
| 569 | + * | |
| 570 | + * <p>{@code Proxy.newProxyInstance} throws | |
| 571 | + * {@code IllegalArgumentException} for the same reasons that | |
| 572 | + * {@code Proxy.getProxyClass} does. | |
| 573 | + * | |
| 574 | + * @param loader the class loader to define the proxy class | |
| 575 | + * @param interfaces the list of interfaces for the proxy class | |
| 576 | + * to implement | |
| 577 | + * @param h the invocation handler to dispatch method invocations to | |
| 578 | + * @return a proxy instance with the specified invocation handler of a | |
| 579 | + * proxy class that is defined by the specified class loader | |
| 580 | + * and that implements the specified interfaces | |
| 581 | + * @throws IllegalArgumentException if any of the restrictions on the | |
| 582 | + * parameters that may be passed to {@code getProxyClass} | |
| 583 | + * are violated | |
| 584 | + * @throws NullPointerException if the {@code interfaces} array | |
| 585 | + * argument or any of its elements are {@code null}, or | |
| 586 | + * if the invocation handler, {@code h}, is | |
| 587 | + * {@code null} | |
| 588 | + */ | |
| 589 | + public static Object newProxyInstance(ClassLoader loader, | |
| 590 | + Class<?>[] interfaces, | |
| 591 | + InvocationHandler h) | |
| 592 | + throws IllegalArgumentException | |
| 593 | + { | |
| 594 | + if (h == null) { | |
| 595 | + throw new NullPointerException(); | |
| 596 | + } | |
| 597 | + | |
| 598 | + /* | |
| 599 | + * Look up or generate the designated proxy class. | |
| 600 | + */ | |
| 601 | + Class<?> cl = getProxyClass(loader, interfaces); | |
| 602 | + | |
| 603 | + /* | |
| 604 | + * Invoke its constructor with the designated invocation handler. | |
| 605 | + */ | |
| 606 | + try { | |
| 607 | + Constructor cons = cl.getConstructor(constructorParams); | |
| 608 | + return cons.newInstance(new Object[] { h }); | |
| 609 | + } catch (NoSuchMethodException e) { | |
| 610 | + throw new InternalError(e.toString()); | |
| 611 | + } catch (IllegalAccessException e) { | |
| 612 | + throw new InternalError(e.toString()); | |
| 613 | + } catch (InstantiationException e) { | |
| 614 | + throw new InternalError(e.toString()); | |
| 615 | + } catch (InvocationTargetException e) { | |
| 616 | + throw new InternalError(e.toString()); | |
| 617 | + } | |
| 618 | + } | |
| 619 | + | |
| 620 | + /** | |
| 621 | + * Returns true if and only if the specified class was dynamically | |
| 622 | + * generated to be a proxy class using the {@code getProxyClass} | |
| 623 | + * method or the {@code newProxyInstance} method. | |
| 624 | + * | |
| 625 | + * <p>The reliability of this method is important for the ability | |
| 626 | + * to use it to make security decisions, so its implementation should | |
| 627 | + * not just test if the class in question extends {@code Proxy}. | |
| 628 | + * | |
| 629 | + * @param cl the class to test | |
| 630 | + * @return {@code true} if the class is a proxy class and | |
| 631 | + * {@code false} otherwise | |
| 632 | + * @throws NullPointerException if {@code cl} is {@code null} | |
| 633 | + */ | |
| 634 | + public static boolean isProxyClass(Class<?> cl) { | |
| 635 | + if (cl == null) { | |
| 636 | + throw new NullPointerException(); | |
| 637 | + } | |
| 638 | + | |
| 639 | + return proxyClasses.containsKey(cl); | |
| 640 | + } | |
| 641 | + | |
| 642 | + /** | |
| 643 | + * Returns the invocation handler for the specified proxy instance. | |
| 644 | + * | |
| 645 | + * @param proxy the proxy instance to return the invocation handler for | |
| 646 | + * @return the invocation handler for the proxy instance | |
| 647 | + * @throws IllegalArgumentException if the argument is not a | |
| 648 | + * proxy instance | |
| 649 | + */ | |
| 650 | + public static InvocationHandler getInvocationHandler(Object proxy) | |
| 651 | + throws IllegalArgumentException | |
| 652 | + { | |
| 653 | + /* | |
| 654 | + * Verify that the object is actually a proxy instance. | |
| 655 | + */ | |
| 656 | + if (!isProxyClass(proxy.getClass())) { | |
| 657 | + throw new IllegalArgumentException("not a proxy instance"); | |
| 658 | + } | |
| 659 | + | |
| 660 | + Proxy p = (Proxy) proxy; | |
| 661 | + return p.h; | |
| 662 | + } | |
| 663 | + | |
| 664 | + private static native Class defineClass0(ClassLoader loader, String name, | |
| 665 | + byte[] b, int off, int len); | |
| 666 | +} | |