| 1 | package org.apache.velocity.util.introspection; |
| 2 | |
| 3 | /* |
| 4 | * Copyright 2001,2004 The Apache Software Foundation. |
| 5 | * |
| 6 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 7 | * you may not use this file except in compliance with the License. |
| 8 | * You may obtain a copy of the License at |
| 9 | * |
| 10 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 11 | * |
| 12 | * Unless required by applicable law or agreed to in writing, software |
| 13 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 14 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 15 | * See the License for the specific language governing permissions and |
| 16 | * limitations under the License. |
| 17 | */ |
| 18 | |
| 19 | import java.util.Map; |
| 20 | import java.util.List; |
| 21 | import java.util.Hashtable; |
| 22 | |
| 23 | import java.lang.reflect.Method; |
| 24 | import java.lang.reflect.Modifier; |
| 25 | |
| 26 | /** |
| 27 | * A cache of introspection information for a specific class instance. |
| 28 | * Keys {@link java.lang.Method} objects by a concatenation of the |
| 29 | * method name and the names of classes that make up the parameters. |
| 30 | * |
| 31 | * @author <a href="mailto:jvanzyl@apache.org">Jason van Zyl</a> |
| 32 | * @author <a href="mailto:bob@werken.com">Bob McWhirter</a> |
| 33 | * @author <a href="mailto:szegedia@freemail.hu">Attila Szegedi</a> |
| 34 | * @author <a href="mailto:geirm@optonline.net">Geir Magnusson Jr.</a> |
| 35 | * @version $Id: ClassMap.java,v 1.20.8.1 2004/03/03 23:23:08 geirm Exp $ |
| 36 | */ |
| 37 | public class ClassMap |
| 38 | { |
| 39 | private static final class CacheMiss { } |
| 40 | private static final CacheMiss CACHE_MISS = new CacheMiss(); |
| 41 | private static final Object OBJECT = new Object(); |
| 42 | |
| 43 | /** |
| 44 | * Class passed into the constructor used to as |
| 45 | * the basis for the Method map. |
| 46 | */ |
| 47 | |
| 48 | private Class clazz; |
| 49 | |
| 50 | /** |
| 51 | * Cache of Methods, or CACHE_MISS, keyed by method |
| 52 | * name and actual arguments used to find it. |
| 53 | */ |
| 54 | private Map methodCache = new Hashtable(); |
| 55 | |
| 56 | private MethodMap methodMap = new MethodMap(); |
| 57 | |
| 58 | /** |
| 59 | * Standard constructor |
| 60 | */ |
| 61 | public ClassMap( Class clazz) |
| 62 | { |
| 63 | this.clazz = clazz; |
| 64 | populateMethodCache(); |
| 65 | } |
| 66 | |
| 67 | private ClassMap() |
| 68 | { |
| 69 | } |
| 70 | |
| 71 | /** |
| 72 | * @return the class object whose methods are cached by this map. |
| 73 | */ |
| 74 | Class getCachedClass() |
| 75 | { |
| 76 | return clazz; |
| 77 | } |
| 78 | |
| 79 | /** |
| 80 | * Find a Method using the methodKey |
| 81 | * provided. |
| 82 | * |
| 83 | * Look in the methodMap for an entry. If found, |
| 84 | * it'll either be a CACHE_MISS, in which case we |
| 85 | * simply give up, or it'll be a Method, in which |
| 86 | * case, we return it. |
| 87 | * |
| 88 | * If nothing is found, then we must actually go |
| 89 | * and introspect the method from the MethodMap. |
| 90 | */ |
| 91 | public Method findMethod(String name, Object[] params) |
| 92 | throws MethodMap.AmbiguousException |
| 93 | { |
| 94 | String methodKey = makeMethodKey(name, params); |
| 95 | Object cacheEntry = methodCache.get( methodKey ); |
| 96 | |
| 97 | if (cacheEntry == CACHE_MISS) |
| 98 | { |
| 99 | return null; |
| 100 | } |
| 101 | |
| 102 | if (cacheEntry == null) |
| 103 | { |
| 104 | try |
| 105 | { |
| 106 | cacheEntry = methodMap.find( name, |
| 107 | params ); |
| 108 | } |
| 109 | catch( MethodMap.AmbiguousException ae ) |
| 110 | { |
| 111 | /* |
| 112 | * that's a miss :) |
| 113 | */ |
| 114 | |
| 115 | methodCache.put( methodKey, |
| 116 | CACHE_MISS ); |
| 117 | |
| 118 | throw ae; |
| 119 | } |
| 120 | |
| 121 | if ( cacheEntry == null ) |
| 122 | { |
| 123 | methodCache.put( methodKey, |
| 124 | CACHE_MISS ); |
| 125 | } |
| 126 | else |
| 127 | { |
| 128 | methodCache.put( methodKey, |
| 129 | cacheEntry ); |
| 130 | } |
| 131 | } |
| 132 | |
| 133 | // Yes, this might just be null. |
| 134 | |
| 135 | return (Method) cacheEntry; |
| 136 | } |
| 137 | |
| 138 | /** |
| 139 | * Populate the Map of direct hits. These |
| 140 | * are taken from all the public methods |
| 141 | * that our class provides. |
| 142 | */ |
| 143 | private void populateMethodCache() |
| 144 | { |
| 145 | StringBuffer methodKey; |
| 146 | |
| 147 | /* |
| 148 | * get all publicly accessible methods |
| 149 | */ |
| 150 | |
| 151 | Method[] methods = getAccessibleMethods(clazz); |
| 152 | |
| 153 | /* |
| 154 | * map and cache them |
| 155 | */ |
| 156 | |
| 157 | for (int i = 0; i < methods.length; i++) |
| 158 | { |
| 159 | Method method = methods[i]; |
| 160 | |
| 161 | /* |
| 162 | * now get the 'public method', the method declared by a |
| 163 | * public interface or class. (because the actual implementing |
| 164 | * class may be a facade... |
| 165 | */ |
| 166 | |
| 167 | Method publicMethod = getPublicMethod( method ); |
| 168 | |
| 169 | /* |
| 170 | * it is entirely possible that there is no public method for |
| 171 | * the methods of this class (i.e. in the facade, a method |
| 172 | * that isn't on any of the interfaces or superclass |
| 173 | * in which case, ignore it. Otherwise, map and cache |
| 174 | */ |
| 175 | |
| 176 | if ( publicMethod != null) |
| 177 | { |
| 178 | methodMap.add( publicMethod ); |
| 179 | methodCache.put( makeMethodKey( publicMethod), publicMethod); |
| 180 | } |
| 181 | } |
| 182 | } |
| 183 | |
| 184 | /** |
| 185 | * Make a methodKey for the given method using |
| 186 | * the concatenation of the name and the |
| 187 | * types of the method parameters. |
| 188 | */ |
| 189 | private String makeMethodKey(Method method) |
| 190 | { |
| 191 | Class[] parameterTypes = method.getParameterTypes(); |
| 192 | |
| 193 | StringBuffer methodKey = new StringBuffer(method.getName()); |
| 194 | |
| 195 | for (int j = 0; j < parameterTypes.length; j++) |
| 196 | { |
| 197 | /* |
| 198 | * If the argument type is primitive then we want |
| 199 | * to convert our primitive type signature to the |
| 200 | * corresponding Object type so introspection for |
| 201 | * methods with primitive types will work correctly. |
| 202 | */ |
| 203 | if (parameterTypes[j].isPrimitive()) |
| 204 | { |
| 205 | if (parameterTypes[j].equals(Boolean.TYPE)) |
| 206 | methodKey.append("java.lang.Boolean"); |
| 207 | else if (parameterTypes[j].equals(Byte.TYPE)) |
| 208 | methodKey.append("java.lang.Byte"); |
| 209 | else if (parameterTypes[j].equals(Character.TYPE)) |
| 210 | methodKey.append("java.lang.Character"); |
| 211 | else if (parameterTypes[j].equals(Double.TYPE)) |
| 212 | methodKey.append("java.lang.Double"); |
| 213 | else if (parameterTypes[j].equals(Float.TYPE)) |
| 214 | methodKey.append("java.lang.Float"); |
| 215 | else if (parameterTypes[j].equals(Integer.TYPE)) |
| 216 | methodKey.append("java.lang.Integer"); |
| 217 | else if (parameterTypes[j].equals(Long.TYPE)) |
| 218 | methodKey.append("java.lang.Long"); |
| 219 | else if (parameterTypes[j].equals(Short.TYPE)) |
| 220 | methodKey.append("java.lang.Short"); |
| 221 | } |
| 222 | else |
| 223 | { |
| 224 | methodKey.append(parameterTypes[j].getName()); |
| 225 | } |
| 226 | } |
| 227 | |
| 228 | return methodKey.toString(); |
| 229 | } |
| 230 | |
| 231 | private static String makeMethodKey(String method, Object[] params) |
| 232 | { |
| 233 | StringBuffer methodKey = new StringBuffer().append(method); |
| 234 | |
| 235 | for (int j = 0; j < params.length; j++) |
| 236 | { |
| 237 | Object arg = params[j]; |
| 238 | |
| 239 | if (arg == null) |
| 240 | { |
| 241 | arg = OBJECT; |
| 242 | } |
| 243 | |
| 244 | methodKey.append(arg.getClass().getName()); |
| 245 | } |
| 246 | |
| 247 | return methodKey.toString(); |
| 248 | } |
| 249 | |
| 250 | /** |
| 251 | * Retrieves public methods for a class. In case the class is not |
| 252 | * public, retrieves methods with same signature as its public methods |
| 253 | * from public superclasses and interfaces (if they exist). Basically |
| 254 | * upcasts every method to the nearest acccessible method. |
| 255 | */ |
| 256 | private static Method[] getAccessibleMethods(Class clazz) |
| 257 | { |
| 258 | Method[] methods = clazz.getMethods(); |
| 259 | |
| 260 | /* |
| 261 | * Short circuit for the (hopefully) majority of cases where the |
| 262 | * clazz is public |
| 263 | */ |
| 264 | |
| 265 | if (Modifier.isPublic(clazz.getModifiers())) |
| 266 | { |
| 267 | return methods; |
| 268 | } |
| 269 | |
| 270 | /* |
| 271 | * No luck - the class is not public, so we're going the longer way. |
| 272 | */ |
| 273 | |
| 274 | MethodInfo[] methodInfos = new MethodInfo[methods.length]; |
| 275 | |
| 276 | for(int i = methods.length; i-- > 0; ) |
| 277 | { |
| 278 | methodInfos[i] = new MethodInfo(methods[i]); |
| 279 | } |
| 280 | |
| 281 | int upcastCount = getAccessibleMethods(clazz, methodInfos, 0); |
| 282 | |
| 283 | /* |
| 284 | * Reallocate array in case some method had no accessible counterpart. |
| 285 | */ |
| 286 | |
| 287 | if(upcastCount < methods.length) |
| 288 | { |
| 289 | methods = new Method[upcastCount]; |
| 290 | } |
| 291 | |
| 292 | int j = 0; |
| 293 | for(int i = 0; i < methodInfos.length; ++i) |
| 294 | { |
| 295 | MethodInfo methodInfo = methodInfos[i]; |
| 296 | if(methodInfo.upcast) |
| 297 | { |
| 298 | methods[j++] = methodInfo.method; |
| 299 | } |
| 300 | } |
| 301 | return methods; |
| 302 | } |
| 303 | |
| 304 | /** |
| 305 | * Recursively finds a match for each method, starting with the class, and then |
| 306 | * searching the superclass and interfaces. |
| 307 | * |
| 308 | * @param clazz Class to check |
| 309 | * @param methodInfos array of methods we are searching to match |
| 310 | * @param upcastCount current number of methods we have matched |
| 311 | * @return count of matched methods |
| 312 | */ |
| 313 | private static int getAccessibleMethods( Class clazz, MethodInfo[] methodInfos, int upcastCount) |
| 314 | { |
| 315 | int l = methodInfos.length; |
| 316 | |
| 317 | /* |
| 318 | * if this class is public, then check each of the currently |
| 319 | * 'non-upcasted' methods to see if we have a match |
| 320 | */ |
| 321 | |
| 322 | if( Modifier.isPublic(clazz.getModifiers()) ) |
| 323 | { |
| 324 | for(int i = 0; i < l && upcastCount < l; ++i) |
| 325 | { |
| 326 | try |
| 327 | { |
| 328 | MethodInfo methodInfo = methodInfos[i]; |
| 329 | |
| 330 | if(!methodInfo.upcast) |
| 331 | { |
| 332 | methodInfo.tryUpcasting(clazz); |
| 333 | upcastCount++; |
| 334 | } |
| 335 | } |
| 336 | catch(NoSuchMethodException e) |
| 337 | { |
| 338 | /* |
| 339 | * Intentionally ignored - it means |
| 340 | * it wasn't found in the current class |
| 341 | */ |
| 342 | } |
| 343 | } |
| 344 | |
| 345 | /* |
| 346 | * Short circuit if all methods were upcast |
| 347 | */ |
| 348 | |
| 349 | if(upcastCount == l) |
| 350 | { |
| 351 | return upcastCount; |
| 352 | } |
| 353 | } |
| 354 | |
| 355 | /* |
| 356 | * Examine superclass |
| 357 | */ |
| 358 | |
| 359 | Class superclazz = clazz.getSuperclass(); |
| 360 | |
| 361 | if(superclazz != null) |
| 362 | { |
| 363 | upcastCount = getAccessibleMethods(superclazz , methodInfos, upcastCount); |
| 364 | |
| 365 | /* |
| 366 | * Short circuit if all methods were upcast |
| 367 | */ |
| 368 | |
| 369 | if(upcastCount == l) |
| 370 | { |
| 371 | return upcastCount; |
| 372 | } |
| 373 | } |
| 374 | |
| 375 | /* |
| 376 | * Examine interfaces. Note we do it even if superclazz == null. |
| 377 | * This is redundant as currently java.lang.Object does not implement |
| 378 | * any interfaces, however nothing guarantees it will not in future. |
| 379 | */ |
| 380 | |
| 381 | Class[] interfaces = clazz.getInterfaces(); |
| 382 | |
| 383 | for(int i = interfaces.length; i-- > 0; ) |
| 384 | { |
| 385 | upcastCount = getAccessibleMethods(interfaces[i], methodInfos, upcastCount); |
| 386 | |
| 387 | /* |
| 388 | * Short circuit if all methods were upcast |
| 389 | */ |
| 390 | |
| 391 | if(upcastCount == l) |
| 392 | { |
| 393 | return upcastCount; |
| 394 | } |
| 395 | } |
| 396 | |
| 397 | return upcastCount; |
| 398 | } |
| 399 | |
| 400 | /** |
| 401 | * For a given method, retrieves its publicly accessible counterpart. |
| 402 | * This method will look for a method with same name |
| 403 | * and signature declared in a public superclass or implemented interface of this |
| 404 | * method's declaring class. This counterpart method is publicly callable. |
| 405 | * |
| 406 | * @param method a method whose publicly callable counterpart is requested. |
| 407 | * @return the publicly callable counterpart method. Note that if the parameter |
| 408 | * method is itself declared by a public class, this method is an identity |
| 409 | * function. |
| 410 | */ |
| 411 | public static Method getPublicMethod(Method method) |
| 412 | { |
| 413 | Class clazz = method.getDeclaringClass(); |
| 414 | |
| 415 | /* |
| 416 | * Short circuit for (hopefully the majority of) cases where the declaring |
| 417 | * class is public. |
| 418 | */ |
| 419 | |
| 420 | if((clazz.getModifiers() & Modifier.PUBLIC) != 0) |
| 421 | { |
| 422 | return method; |
| 423 | } |
| 424 | |
| 425 | return getPublicMethod(clazz, method.getName(), method.getParameterTypes()); |
| 426 | } |
| 427 | |
| 428 | /** |
| 429 | * Looks up the method with specified name and signature in the first public |
| 430 | * superclass or implemented interface of the class. |
| 431 | * |
| 432 | * @param class the class whose method is sought |
| 433 | * @param name the name of the method |
| 434 | * @param paramTypes the classes of method parameters |
| 435 | */ |
| 436 | private static Method getPublicMethod(Class clazz, String name, Class[] paramTypes) |
| 437 | { |
| 438 | /* |
| 439 | * if this class is public, then try to get it |
| 440 | */ |
| 441 | |
| 442 | if((clazz.getModifiers() & Modifier.PUBLIC) != 0) |
| 443 | { |
| 444 | try |
| 445 | { |
| 446 | return clazz.getMethod(name, paramTypes); |
| 447 | } |
| 448 | catch(NoSuchMethodException e) |
| 449 | { |
| 450 | /* |
| 451 | * If the class does not have the method, then neither its |
| 452 | * superclass nor any of its interfaces has it so quickly return |
| 453 | * null. |
| 454 | */ |
| 455 | return null; |
| 456 | } |
| 457 | } |
| 458 | |
| 459 | /* |
| 460 | * try the superclass |
| 461 | */ |
| 462 | |
| 463 | |
| 464 | Class superclazz = clazz.getSuperclass(); |
| 465 | |
| 466 | if ( superclazz != null ) |
| 467 | { |
| 468 | Method superclazzMethod = getPublicMethod(superclazz, name, paramTypes); |
| 469 | |
| 470 | if(superclazzMethod != null) |
| 471 | { |
| 472 | return superclazzMethod; |
| 473 | } |
| 474 | } |
| 475 | |
| 476 | /* |
| 477 | * and interfaces |
| 478 | */ |
| 479 | |
| 480 | Class[] interfaces = clazz.getInterfaces(); |
| 481 | |
| 482 | for(int i = 0; i < interfaces.length; ++i) |
| 483 | { |
| 484 | Method interfaceMethod = getPublicMethod(interfaces[i], name, paramTypes); |
| 485 | |
| 486 | if(interfaceMethod != null) |
| 487 | { |
| 488 | return interfaceMethod; |
| 489 | } |
| 490 | } |
| 491 | |
| 492 | return null; |
| 493 | } |
| 494 | |
| 495 | /** |
| 496 | * Used for the iterative discovery process for public methods. |
| 497 | */ |
| 498 | private static final class MethodInfo |
| 499 | { |
| 500 | Method method; |
| 501 | String name; |
| 502 | Class[] parameterTypes; |
| 503 | boolean upcast; |
| 504 | |
| 505 | MethodInfo(Method method) |
| 506 | { |
| 507 | this.method = null; |
| 508 | name = method.getName(); |
| 509 | parameterTypes = method.getParameterTypes(); |
| 510 | upcast = false; |
| 511 | } |
| 512 | |
| 513 | void tryUpcasting(Class clazz) |
| 514 | throws NoSuchMethodException |
| 515 | { |
| 516 | method = clazz.getMethod(name, parameterTypes); |
| 517 | name = null; |
| 518 | parameterTypes = null; |
| 519 | upcast = true; |
| 520 | } |
| 521 | } |
| 522 | } |