J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 1999-2006 Sun Microsystems, Inc. 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. Sun designates this |
| 8 | * particular file as subject to the "Classpath" exception as provided |
| 9 | * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| 22 | * CA 95054 USA or visit www.sun.com if you need additional information or |
| 23 | * have any 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.WeakHashMap; |
| 37 | import sun.misc.ProxyGenerator; |
| 38 | |
| 39 | /** |
| 40 | * {@code Proxy} provides static methods for creating dynamic proxy |
| 41 | * classes and instances, and it is also the superclass of all |
| 42 | * dynamic proxy classes created by those methods. |
| 43 | * |
| 44 | * <p>To create a proxy for some interface {@code Foo}: |
| 45 | * <pre> |
| 46 | * InvocationHandler handler = new MyInvocationHandler(...); |
| 47 | * Class proxyClass = Proxy.getProxyClass( |
| 48 | * Foo.class.getClassLoader(), new Class[] { Foo.class }); |
| 49 | * Foo f = (Foo) proxyClass. |
| 50 | * getConstructor(new Class[] { InvocationHandler.class }). |
| 51 | * newInstance(new Object[] { handler }); |
| 52 | * </pre> |
| 53 | * or more simply: |
| 54 | * <pre> |
| 55 | * Foo f = (Foo) Proxy.newProxyInstance(Foo.class.getClassLoader(), |
| 56 | * new Class[] { Foo.class }, |
| 57 | * handler); |
| 58 | * </pre> |
| 59 | * |
| 60 | * <p>A <i>dynamic proxy class</i> (simply referred to as a <i>proxy |
| 61 | * class</i> below) is a class that implements a list of interfaces |
| 62 | * specified at runtime when the class is created, with behavior as |
| 63 | * described below. |
| 64 | * |
| 65 | * A <i>proxy interface</i> is such an interface that is implemented |
| 66 | * by a proxy class. |
| 67 | * |
| 68 | * A <i>proxy instance</i> is an instance of a proxy class. |
| 69 | * |
| 70 | * Each proxy instance has an associated <i>invocation handler</i> |
| 71 | * object, which implements the interface {@link InvocationHandler}. |
| 72 | * A method invocation on a proxy instance through one of its proxy |
| 73 | * interfaces will be dispatched to the {@link InvocationHandler#invoke |
| 74 | * invoke} method of the instance's invocation handler, passing the proxy |
| 75 | * instance, a {@code java.lang.reflect.Method} object identifying |
| 76 | * the method that was invoked, and an array of type {@code Object} |
| 77 | * containing the arguments. The invocation handler processes the |
| 78 | * encoded method invocation as appropriate and the result that it |
| 79 | * returns will be returned as the result of the method invocation on |
| 80 | * the proxy instance. |
| 81 | * |
| 82 | * <p>A proxy class has the following properties: |
| 83 | * |
| 84 | * <ul> |
| 85 | * <li>Proxy classes are public, final, and not abstract. |
| 86 | * |
| 87 | * <li>The unqualified name of a proxy class is unspecified. The space |
| 88 | * of class names that begin with the string {@code "$Proxy"} |
| 89 | * should be, however, reserved for proxy classes. |
| 90 | * |
| 91 | * <li>A proxy class extends {@code java.lang.reflect.Proxy}. |
| 92 | * |
| 93 | * <li>A proxy class implements exactly the interfaces specified at its |
| 94 | * creation, in the same order. |
| 95 | * |
| 96 | * <li>If a proxy class implements a non-public interface, then it will |
| 97 | * be defined in the same package as that interface. Otherwise, the |
| 98 | * package of a proxy class is also unspecified. Note that package |
| 99 | * sealing will not prevent a proxy class from being successfully defined |
| 100 | * in a particular package at runtime, and neither will classes already |
| 101 | * defined by the same class loader and the same package with particular |
| 102 | * signers. |
| 103 | * |
| 104 | * <li>Since a proxy class implements all of the interfaces specified at |
| 105 | * its creation, invoking {@code getInterfaces} on its |
| 106 | * {@code Class} object will return an array containing the same |
| 107 | * list of interfaces (in the order specified at its creation), invoking |
| 108 | * {@code getMethods} on its {@code Class} object will return |
| 109 | * an array of {@code Method} objects that include all of the |
| 110 | * methods in those interfaces, and invoking {@code getMethod} will |
| 111 | * find methods in the proxy interfaces as would be expected. |
| 112 | * |
| 113 | * <li>The {@link Proxy#isProxyClass Proxy.isProxyClass} method will |
| 114 | * return true if it is passed a proxy class-- a class returned by |
| 115 | * {@code Proxy.getProxyClass} or the class of an object returned by |
| 116 | * {@code Proxy.newProxyInstance}-- and false otherwise. |
| 117 | * |
| 118 | * <li>The {@code java.security.ProtectionDomain} of a proxy class |
| 119 | * is the same as that of system classes loaded by the bootstrap class |
| 120 | * loader, such as {@code java.lang.Object}, because the code for a |
| 121 | * proxy class is generated by trusted system code. This protection |
| 122 | * domain will typically be granted |
| 123 | * {@code java.security.AllPermission}. |
| 124 | * |
| 125 | * <li>Each proxy class has one public constructor that takes one argument, |
| 126 | * an implementation of the interface {@link InvocationHandler}, to set |
| 127 | * the invocation handler for a proxy instance. Rather than having to use |
| 128 | * the reflection API to access the public constructor, a proxy instance |
| 129 | * can be also be created by calling the {@link Proxy#newProxyInstance |
| 130 | * Proxy.newProxyInstance} method, which combines the actions of calling |
| 131 | * {@link Proxy#getProxyClass Proxy.getProxyClass} with invoking the |
| 132 | * constructor with an invocation handler. |
| 133 | * </ul> |
| 134 | * |
| 135 | * <p>A proxy instance has the following properties: |
| 136 | * |
| 137 | * <ul> |
| 138 | * <li>Given a proxy instance {@code proxy} and one of the |
| 139 | * interfaces implemented by its proxy class {@code Foo}, the |
| 140 | * following expression will return true: |
| 141 | * <pre> |
| 142 | * {@code proxy instanceof Foo} |
| 143 | * </pre> |
| 144 | * and the following cast operation will succeed (rather than throwing |
| 145 | * a {@code ClassCastException}): |
| 146 | * <pre> |
| 147 | * {@code (Foo) proxy} |
| 148 | * </pre> |
| 149 | * |
| 150 | * <li>Each proxy instance has an associated invocation handler, the one |
| 151 | * that was passed to its constructor. The static |
| 152 | * {@link Proxy#getInvocationHandler Proxy.getInvocationHandler} method |
| 153 | * will return the invocation handler associated with the proxy instance |
| 154 | * passed as its argument. |
| 155 | * |
| 156 | * <li>An interface method invocation on a proxy instance will be |
| 157 | * encoded and dispatched to the invocation handler's {@link |
| 158 | * InvocationHandler#invoke invoke} method as described in the |
| 159 | * documentation for that method. |
| 160 | * |
| 161 | * <li>An invocation of the {@code hashCode}, |
| 162 | * {@code equals}, or {@code toString} methods declared in |
| 163 | * {@code java.lang.Object} on a proxy instance will be encoded and |
| 164 | * dispatched to the invocation handler's {@code invoke} method in |
| 165 | * the same manner as interface method invocations are encoded and |
| 166 | * dispatched, as described above. The declaring class of the |
| 167 | * {@code Method} object passed to {@code invoke} will be |
| 168 | * {@code java.lang.Object}. Other public methods of a proxy |
| 169 | * instance inherited from {@code java.lang.Object} are not |
| 170 | * overridden by a proxy class, so invocations of those methods behave |
| 171 | * like they do for instances of {@code java.lang.Object}. |
| 172 | * </ul> |
| 173 | * |
| 174 | * <h3>Methods Duplicated in Multiple Proxy Interfaces</h3> |
| 175 | * |
| 176 | * <p>When two or more interfaces of a proxy class contain a method with |
| 177 | * the same name and parameter signature, the order of the proxy class's |
| 178 | * interfaces becomes significant. When such a <i>duplicate method</i> |
| 179 | * is invoked on a proxy instance, the {@code Method} object passed |
| 180 | * to the invocation handler will not necessarily be the one whose |
| 181 | * declaring class is assignable from the reference type of the interface |
| 182 | * that the proxy's method was invoked through. This limitation exists |
| 183 | * because the corresponding method implementation in the generated proxy |
| 184 | * class cannot determine which interface it was invoked through. |
| 185 | * Therefore, when a duplicate method is invoked on a proxy instance, |
| 186 | * the {@code Method} object for the method in the foremost interface |
| 187 | * that contains the method (either directly or inherited through a |
| 188 | * superinterface) in the proxy class's list of interfaces is passed to |
| 189 | * the invocation handler's {@code invoke} method, regardless of the |
| 190 | * reference type through which the method invocation occurred. |
| 191 | * |
| 192 | * <p>If a proxy interface contains a method with the same name and |
| 193 | * parameter signature as the {@code hashCode}, {@code equals}, |
| 194 | * or {@code toString} methods of {@code java.lang.Object}, |
| 195 | * when such a method is invoked on a proxy instance, the |
| 196 | * {@code Method} object passed to the invocation handler will have |
| 197 | * {@code java.lang.Object} as its declaring class. In other words, |
| 198 | * the public, non-final methods of {@code java.lang.Object} |
| 199 | * logically precede all of the proxy interfaces for the determination of |
| 200 | * which {@code Method} object to pass to the invocation handler. |
| 201 | * |
| 202 | * <p>Note also that when a duplicate method is dispatched to an |
| 203 | * invocation handler, the {@code invoke} method may only throw |
| 204 | * checked exception types that are assignable to one of the exception |
| 205 | * types in the {@code throws} clause of the method in <i>all</i> of |
| 206 | * the proxy interfaces that it can be invoked through. If the |
| 207 | * {@code invoke} method throws a checked exception that is not |
| 208 | * assignable to any of the exception types declared by the method in one |
| 209 | * of the proxy interfaces that it can be invoked through, then an |
| 210 | * unchecked {@code UndeclaredThrowableException} will be thrown by |
| 211 | * the invocation on the proxy instance. This restriction means that not |
| 212 | * all of the exception types returned by invoking |
| 213 | * {@code getExceptionTypes} on the {@code Method} object |
| 214 | * passed to the {@code invoke} method can necessarily be thrown |
| 215 | * successfully by the {@code invoke} method. |
| 216 | * |
| 217 | * @author Peter Jones |
| 218 | * @see InvocationHandler |
| 219 | * @since 1.3 |
| 220 | */ |
| 221 | public class Proxy implements java.io.Serializable { |
| 222 | |
| 223 | private static final long serialVersionUID = -2222568056686623797L; |
| 224 | |
| 225 | /** prefix for all proxy class names */ |
| 226 | private final static String proxyClassNamePrefix = "$Proxy"; |
| 227 | |
| 228 | /** parameter types of a proxy class constructor */ |
| 229 | private final static Class[] constructorParams = |
| 230 | { InvocationHandler.class }; |
| 231 | |
| 232 | /** maps a class loader to the proxy class cache for that loader */ |
| 233 | private static Map loaderToCache = new WeakHashMap(); |
| 234 | |
| 235 | /** marks that a particular proxy class is currently being generated */ |
| 236 | private static Object pendingGenerationMarker = new Object(); |
| 237 | |
| 238 | /** next number to use for generation of unique proxy class names */ |
| 239 | private static long nextUniqueNumber = 0; |
| 240 | private static Object nextUniqueNumberLock = new Object(); |
| 241 | |
| 242 | /** set of all generated proxy classes, for isProxyClass implementation */ |
| 243 | private static Map proxyClasses = |
| 244 | Collections.synchronizedMap(new WeakHashMap()); |
| 245 | |
| 246 | /** |
| 247 | * the invocation handler for this proxy instance. |
| 248 | * @serial |
| 249 | */ |
| 250 | protected InvocationHandler h; |
| 251 | |
| 252 | /** |
| 253 | * Prohibits instantiation. |
| 254 | */ |
| 255 | private Proxy() { |
| 256 | } |
| 257 | |
| 258 | /** |
| 259 | * Constructs a new {@code Proxy} instance from a subclass |
| 260 | * (typically, a dynamic proxy class) with the specified value |
| 261 | * for its invocation handler. |
| 262 | * |
| 263 | * @param h the invocation handler for this proxy instance |
| 264 | */ |
| 265 | protected Proxy(InvocationHandler h) { |
| 266 | this.h = h; |
| 267 | } |
| 268 | |
| 269 | /** |
| 270 | * Returns the {@code java.lang.Class} object for a proxy class |
| 271 | * given a class loader and an array of interfaces. The proxy class |
| 272 | * will be defined by the specified class loader and will implement |
| 273 | * all of the supplied interfaces. If a proxy class for the same |
| 274 | * permutation of interfaces has already been defined by the class |
| 275 | * loader, then the existing proxy class will be returned; otherwise, |
| 276 | * a proxy class for those interfaces will be generated dynamically |
| 277 | * and defined by the class loader. |
| 278 | * |
| 279 | * <p>There are several restrictions on the parameters that may be |
| 280 | * passed to {@code Proxy.getProxyClass}: |
| 281 | * |
| 282 | * <ul> |
| 283 | * <li>All of the {@code Class} objects in the |
| 284 | * {@code interfaces} array must represent interfaces, not |
| 285 | * classes or primitive types. |
| 286 | * |
| 287 | * <li>No two elements in the {@code interfaces} array may |
| 288 | * refer to identical {@code Class} objects. |
| 289 | * |
| 290 | * <li>All of the interface types must be visible by name through the |
| 291 | * specified class loader. In other words, for class loader |
| 292 | * {@code cl} and every interface {@code i}, the following |
| 293 | * expression must be true: |
| 294 | * <pre> |
| 295 | * Class.forName(i.getName(), false, cl) == i |
| 296 | * </pre> |
| 297 | * |
| 298 | * <li>All non-public interfaces must be in the same package; |
| 299 | * otherwise, it would not be possible for the proxy class to |
| 300 | * implement all of the interfaces, regardless of what package it is |
| 301 | * defined in. |
| 302 | * |
| 303 | * <li>For any set of member methods of the specified interfaces |
| 304 | * that have the same signature: |
| 305 | * <ul> |
| 306 | * <li>If the return type of any of the methods is a primitive |
| 307 | * type or void, then all of the methods must have that same |
| 308 | * return type. |
| 309 | * <li>Otherwise, one of the methods must have a return type that |
| 310 | * is assignable to all of the return types of the rest of the |
| 311 | * methods. |
| 312 | * </ul> |
| 313 | * |
| 314 | * <li>The resulting proxy class must not exceed any limits imposed |
| 315 | * on classes by the virtual machine. For example, the VM may limit |
| 316 | * the number of interfaces that a class may implement to 65535; in |
| 317 | * that case, the size of the {@code interfaces} array must not |
| 318 | * exceed 65535. |
| 319 | * </ul> |
| 320 | * |
| 321 | * <p>If any of these restrictions are violated, |
| 322 | * {@code Proxy.getProxyClass} will throw an |
| 323 | * {@code IllegalArgumentException}. If the {@code interfaces} |
| 324 | * array argument or any of its elements are {@code null}, a |
| 325 | * {@code NullPointerException} will be thrown. |
| 326 | * |
| 327 | * <p>Note that the order of the specified proxy interfaces is |
| 328 | * significant: two requests for a proxy class with the same combination |
| 329 | * of interfaces but in a different order will result in two distinct |
| 330 | * proxy classes. |
| 331 | * |
| 332 | * @param loader the class loader to define the proxy class |
| 333 | * @param interfaces the list of interfaces for the proxy class |
| 334 | * to implement |
| 335 | * @return a proxy class that is defined in the specified class loader |
| 336 | * and that implements the specified interfaces |
| 337 | * @throws IllegalArgumentException if any of the restrictions on the |
| 338 | * parameters that may be passed to {@code getProxyClass} |
| 339 | * are violated |
| 340 | * @throws NullPointerException if the {@code interfaces} array |
| 341 | * argument or any of its elements are {@code null} |
| 342 | */ |
| 343 | public static Class<?> getProxyClass(ClassLoader loader, |
| 344 | Class<?>... interfaces) |
| 345 | throws IllegalArgumentException |
| 346 | { |
| 347 | if (interfaces.length > 65535) { |
| 348 | throw new IllegalArgumentException("interface limit exceeded"); |
| 349 | } |
| 350 | |
| 351 | Class proxyClass = null; |
| 352 | |
| 353 | /* collect interface names to use as key for proxy class cache */ |
| 354 | String[] interfaceNames = new String[interfaces.length]; |
| 355 | |
| 356 | Set interfaceSet = new HashSet(); // for detecting duplicates |
| 357 | |
| 358 | for (int i = 0; i < interfaces.length; i++) { |
| 359 | /* |
| 360 | * Verify that the class loader resolves the name of this |
| 361 | * interface to the same Class object. |
| 362 | */ |
| 363 | String interfaceName = interfaces[i].getName(); |
| 364 | Class interfaceClass = null; |
| 365 | try { |
| 366 | interfaceClass = Class.forName(interfaceName, false, loader); |
| 367 | } catch (ClassNotFoundException e) { |
| 368 | } |
| 369 | if (interfaceClass != interfaces[i]) { |
| 370 | throw new IllegalArgumentException( |
| 371 | interfaces[i] + " is not visible from class loader"); |
| 372 | } |
| 373 | |
| 374 | /* |
| 375 | * Verify that the Class object actually represents an |
| 376 | * interface. |
| 377 | */ |
| 378 | if (!interfaceClass.isInterface()) { |
| 379 | throw new IllegalArgumentException( |
| 380 | interfaceClass.getName() + " is not an interface"); |
| 381 | } |
| 382 | |
| 383 | /* |
| 384 | * Verify that this interface is not a duplicate. |
| 385 | */ |
| 386 | if (interfaceSet.contains(interfaceClass)) { |
| 387 | throw new IllegalArgumentException( |
| 388 | "repeated interface: " + interfaceClass.getName()); |
| 389 | } |
| 390 | interfaceSet.add(interfaceClass); |
| 391 | |
| 392 | interfaceNames[i] = interfaceName; |
| 393 | } |
| 394 | |
| 395 | /* |
| 396 | * Using string representations of the proxy interfaces as |
| 397 | * keys in the proxy class cache (instead of their Class |
| 398 | * objects) is sufficient because we require the proxy |
| 399 | * interfaces to be resolvable by name through the supplied |
| 400 | * class loader, and it has the advantage that using a string |
| 401 | * representation of a class makes for an implicit weak |
| 402 | * reference to the class. |
| 403 | */ |
| 404 | Object key = Arrays.asList(interfaceNames); |
| 405 | |
| 406 | /* |
| 407 | * Find or create the proxy class cache for the class loader. |
| 408 | */ |
| 409 | Map cache; |
| 410 | synchronized (loaderToCache) { |
| 411 | cache = (Map) loaderToCache.get(loader); |
| 412 | if (cache == null) { |
| 413 | cache = new HashMap(); |
| 414 | loaderToCache.put(loader, cache); |
| 415 | } |
| 416 | /* |
| 417 | * This mapping will remain valid for the duration of this |
| 418 | * method, without further synchronization, because the mapping |
| 419 | * will only be removed if the class loader becomes unreachable. |
| 420 | */ |
| 421 | } |
| 422 | |
| 423 | /* |
| 424 | * Look up the list of interfaces in the proxy class cache using |
| 425 | * the key. This lookup will result in one of three possible |
| 426 | * kinds of values: |
| 427 | * null, if there is currently no proxy class for the list of |
| 428 | * interfaces in the class loader, |
| 429 | * the pendingGenerationMarker object, if a proxy class for the |
| 430 | * list of interfaces is currently being generated, |
| 431 | * or a weak reference to a Class object, if a proxy class for |
| 432 | * the list of interfaces has already been generated. |
| 433 | */ |
| 434 | synchronized (cache) { |
| 435 | /* |
| 436 | * Note that we need not worry about reaping the cache for |
| 437 | * entries with cleared weak references because if a proxy class |
| 438 | * has been garbage collected, its class loader will have been |
| 439 | * garbage collected as well, so the entire cache will be reaped |
| 440 | * from the loaderToCache map. |
| 441 | */ |
| 442 | do { |
| 443 | Object value = cache.get(key); |
| 444 | if (value instanceof Reference) { |
| 445 | proxyClass = (Class) ((Reference) value).get(); |
| 446 | } |
| 447 | if (proxyClass != null) { |
| 448 | // proxy class already generated: return it |
| 449 | return proxyClass; |
| 450 | } else if (value == pendingGenerationMarker) { |
| 451 | // proxy class being generated: wait for it |
| 452 | try { |
| 453 | cache.wait(); |
| 454 | } catch (InterruptedException e) { |
| 455 | /* |
| 456 | * The class generation that we are waiting for should |
| 457 | * take a small, bounded time, so we can safely ignore |
| 458 | * thread interrupts here. |
| 459 | */ |
| 460 | } |
| 461 | continue; |
| 462 | } else { |
| 463 | /* |
| 464 | * No proxy class for this list of interfaces has been |
| 465 | * generated or is being generated, so we will go and |
| 466 | * generate it now. Mark it as pending generation. |
| 467 | */ |
| 468 | cache.put(key, pendingGenerationMarker); |
| 469 | break; |
| 470 | } |
| 471 | } while (true); |
| 472 | } |
| 473 | |
| 474 | try { |
| 475 | String proxyPkg = null; // package to define proxy class in |
| 476 | |
| 477 | /* |
| 478 | * Record the package of a non-public proxy interface so that the |
| 479 | * proxy class will be defined in the same package. Verify that |
| 480 | * all non-public proxy interfaces are in the same package. |
| 481 | */ |
| 482 | for (int i = 0; i < interfaces.length; i++) { |
| 483 | int flags = interfaces[i].getModifiers(); |
| 484 | if (!Modifier.isPublic(flags)) { |
| 485 | String name = interfaces[i].getName(); |
| 486 | int n = name.lastIndexOf('.'); |
| 487 | String pkg = ((n == -1) ? "" : name.substring(0, n + 1)); |
| 488 | if (proxyPkg == null) { |
| 489 | proxyPkg = pkg; |
| 490 | } else if (!pkg.equals(proxyPkg)) { |
| 491 | throw new IllegalArgumentException( |
| 492 | "non-public interfaces from different packages"); |
| 493 | } |
| 494 | } |
| 495 | } |
| 496 | |
| 497 | if (proxyPkg == null) { // if no non-public proxy interfaces, |
| 498 | proxyPkg = ""; // use the unnamed package |
| 499 | } |
| 500 | |
| 501 | { |
| 502 | /* |
| 503 | * Choose a name for the proxy class to generate. |
| 504 | */ |
| 505 | long num; |
| 506 | synchronized (nextUniqueNumberLock) { |
| 507 | num = nextUniqueNumber++; |
| 508 | } |
| 509 | String proxyName = proxyPkg + proxyClassNamePrefix + num; |
| 510 | /* |
| 511 | * Verify that the class loader hasn't already |
| 512 | * defined a class with the chosen name. |
| 513 | */ |
| 514 | |
| 515 | /* |
| 516 | * Generate the specified proxy class. |
| 517 | */ |
| 518 | byte[] proxyClassFile = ProxyGenerator.generateProxyClass( |
| 519 | proxyName, interfaces); |
| 520 | try { |
| 521 | proxyClass = defineClass0(loader, proxyName, |
| 522 | proxyClassFile, 0, proxyClassFile.length); |
| 523 | } catch (ClassFormatError e) { |
| 524 | /* |
| 525 | * A ClassFormatError here means that (barring bugs in the |
| 526 | * proxy class generation code) there was some other |
| 527 | * invalid aspect of the arguments supplied to the proxy |
| 528 | * class creation (such as virtual machine limitations |
| 529 | * exceeded). |
| 530 | */ |
| 531 | throw new IllegalArgumentException(e.toString()); |
| 532 | } |
| 533 | } |
| 534 | // add to set of all generated proxy classes, for isProxyClass |
| 535 | proxyClasses.put(proxyClass, null); |
| 536 | |
| 537 | } finally { |
| 538 | /* |
| 539 | * We must clean up the "pending generation" state of the proxy |
| 540 | * class cache entry somehow. If a proxy class was successfully |
| 541 | * generated, store it in the cache (with a weak reference); |
| 542 | * otherwise, remove the reserved entry. In all cases, notify |
| 543 | * all waiters on reserved entries in this cache. |
| 544 | */ |
| 545 | synchronized (cache) { |
| 546 | if (proxyClass != null) { |
| 547 | cache.put(key, new WeakReference(proxyClass)); |
| 548 | } else { |
| 549 | cache.remove(key); |
| 550 | } |
| 551 | cache.notifyAll(); |
| 552 | } |
| 553 | } |
| 554 | return proxyClass; |
| 555 | } |
| 556 | |
| 557 | /** |
| 558 | * Returns an instance of a proxy class for the specified interfaces |
| 559 | * that dispatches method invocations to the specified invocation |
| 560 | * handler. This method is equivalent to: |
| 561 | * <pre> |
| 562 | * Proxy.getProxyClass(loader, interfaces). |
| 563 | * getConstructor(new Class[] { InvocationHandler.class }). |
| 564 | * newInstance(new Object[] { handler }); |
| 565 | * </pre> |
| 566 | * |
| 567 | * <p>{@code Proxy.newProxyInstance} throws |
| 568 | * {@code IllegalArgumentException} for the same reasons that |
| 569 | * {@code Proxy.getProxyClass} does. |
| 570 | * |
| 571 | * @param loader the class loader to define the proxy class |
| 572 | * @param interfaces the list of interfaces for the proxy class |
| 573 | * to implement |
| 574 | * @param h the invocation handler to dispatch method invocations to |
| 575 | * @return a proxy instance with the specified invocation handler of a |
| 576 | * proxy class that is defined by the specified class loader |
| 577 | * and that implements the specified interfaces |
| 578 | * @throws IllegalArgumentException if any of the restrictions on the |
| 579 | * parameters that may be passed to {@code getProxyClass} |
| 580 | * are violated |
| 581 | * @throws NullPointerException if the {@code interfaces} array |
| 582 | * argument or any of its elements are {@code null}, or |
| 583 | * if the invocation handler, {@code h}, is |
| 584 | * {@code null} |
| 585 | */ |
| 586 | public static Object newProxyInstance(ClassLoader loader, |
| 587 | Class<?>[] interfaces, |
| 588 | InvocationHandler h) |
| 589 | throws IllegalArgumentException |
| 590 | { |
| 591 | if (h == null) { |
| 592 | throw new NullPointerException(); |
| 593 | } |
| 594 | |
| 595 | /* |
| 596 | * Look up or generate the designated proxy class. |
| 597 | */ |
| 598 | Class cl = getProxyClass(loader, interfaces); |
| 599 | |
| 600 | /* |
| 601 | * Invoke its constructor with the designated invocation handler. |
| 602 | */ |
| 603 | try { |
| 604 | Constructor cons = cl.getConstructor(constructorParams); |
| 605 | return (Object) cons.newInstance(new Object[] { h }); |
| 606 | } catch (NoSuchMethodException e) { |
| 607 | throw new InternalError(e.toString()); |
| 608 | } catch (IllegalAccessException e) { |
| 609 | throw new InternalError(e.toString()); |
| 610 | } catch (InstantiationException e) { |
| 611 | throw new InternalError(e.toString()); |
| 612 | } catch (InvocationTargetException e) { |
| 613 | throw new InternalError(e.toString()); |
| 614 | } |
| 615 | } |
| 616 | |
| 617 | /** |
| 618 | * Returns true if and only if the specified class was dynamically |
| 619 | * generated to be a proxy class using the {@code getProxyClass} |
| 620 | * method or the {@code newProxyInstance} method. |
| 621 | * |
| 622 | * <p>The reliability of this method is important for the ability |
| 623 | * to use it to make security decisions, so its implementation should |
| 624 | * not just test if the class in question extends {@code Proxy}. |
| 625 | * |
| 626 | * @param cl the class to test |
| 627 | * @return {@code true} if the class is a proxy class and |
| 628 | * {@code false} otherwise |
| 629 | * @throws NullPointerException if {@code cl} is {@code null} |
| 630 | */ |
| 631 | public static boolean isProxyClass(Class<?> cl) { |
| 632 | if (cl == null) { |
| 633 | throw new NullPointerException(); |
| 634 | } |
| 635 | |
| 636 | return proxyClasses.containsKey(cl); |
| 637 | } |
| 638 | |
| 639 | /** |
| 640 | * Returns the invocation handler for the specified proxy instance. |
| 641 | * |
| 642 | * @param proxy the proxy instance to return the invocation handler for |
| 643 | * @return the invocation handler for the proxy instance |
| 644 | * @throws IllegalArgumentException if the argument is not a |
| 645 | * proxy instance |
| 646 | */ |
| 647 | public static InvocationHandler getInvocationHandler(Object proxy) |
| 648 | throws IllegalArgumentException |
| 649 | { |
| 650 | /* |
| 651 | * Verify that the object is actually a proxy instance. |
| 652 | */ |
| 653 | if (!isProxyClass(proxy.getClass())) { |
| 654 | throw new IllegalArgumentException("not a proxy instance"); |
| 655 | } |
| 656 | |
| 657 | Proxy p = (Proxy) proxy; |
| 658 | return p.h; |
| 659 | } |
| 660 | |
| 661 | private static native Class defineClass0(ClassLoader loader, String name, |
| 662 | byte[] b, int off, int len); |
| 663 | } |