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