Coverage report

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org.apache.commons.jexl.util.introspection.MethodMap$AmbiguousException |
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1 |  |
     /*
2 |  |
      * Copyright 2001,2004 The Apache Software Foundation.
3 |  |
      *
4 |  |
      * Licensed under the Apache License, Version 2.0 (the "License");
5 |  |
      * you may not use this file except in compliance with the License.
6 |  |
      * You may obtain a copy of the License at
7 |  |
      *
8 |  |
      *      http://www.apache.org/licenses/LICENSE-2.0
9 |  |
      *
10 |  |
      * Unless required by applicable law or agreed to in writing, software
11 |  |
      * distributed under the License is distributed on an "AS IS" BASIS,
12 |  |
      * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 |  |
      * See the License for the specific language governing permissions and
14 |  |
      * limitations under the License.
15 |  |
      */
16 |  |
17 |  |
     package org.apache.commons.jexl.util.introspection;
18 |  |
19 |  |
     import java.lang.reflect.Method;
20 |  |
     import java.util.ArrayList;
21 |  |
     import java.util.Hashtable;
22 |  |
     import java.util.Iterator;
23 |  |
     import java.util.LinkedList;
24 |  |
     import java.util.List;
25 |  |
     import java.util.Map;
26 |  |
27 |  |
     /**
28 |  |
      *
29 |  |
      * @author <a href="mailto:jvanzyl@apache.org">Jason van Zyl</a>
30 |  |
      * @author <a href="mailto:bob@werken.com">Bob McWhirter</a>
31 |  |
      * @author <a href="mailto:Christoph.Reck@dlr.de">Christoph Reck</a>
32 |  |
      * @author <a href="mailto:geirm@optonline.net">Geir Magnusson Jr.</a>
33 |  |
      * @author <a href="mailto:szegedia@freemail.hu">Attila Szegedi</a>
34 |  |
      * @since 1.0
35 |  |
      * @version $Id: MethodMap.java 398495 2006-05-01 01:33:43Z dion $
36 |  |
      */
37 |  |
     public class MethodMap {
38 |  |
         /** whether a method is more specific than a previously compared one. */
39 |  |
         private static final int MORE_SPECIFIC = 0;
40 |  |
         /** whether a method is less specific than a previously compared one. */
41 |  |
         private static final int LESS_SPECIFIC = 1;
42 |  |
         /** A method doesn't match a previously compared one. */
43 |  |
         private static final int INCOMPARABLE = 2;
44 |  |
45 |  |
         /**
46 |  |
          * Keep track of all methods with the same name.
47 |  |
          */
48 |  |
         protected Map methodByNameMap = new Hashtable();
49 |  |
50 |  |
         /**
51 |  |
          * Add a method to a list of methods by name. For a particular class we are
52 |  |
          * keeping track of all the methods with the same name.
53 |  |
          * @param method the method.
54 |  |
          */
55 |  |
         public void add(Method method) {
56 |  |
             String methodName = method.getName();
57 |  |
58 |  |
             List l = get(methodName);
59 |  |
60 |  |
             if (l == null) {
61 |  |
                 l = new ArrayList();
62 |  |
                 methodByNameMap.put(methodName, l);
63 |  |
             }
64 |  |
65 |  |
             l.add(method);
66 |  |
         }
67 |  |
68 |  |
         /**
69 |  |
          * Return a list of methods with the same name.
70 |  |
          *
71 |  |
          * @param key The method name.
72 |  |
          * @return List list of methods
73 |  |
          */
74 |  |
         public List get(String key) {
75 |  |
             return (List) methodByNameMap.get(key);
76 |  |
         }
77 |  |
78 |  |
         /**
79 |  |
          * <p>
80 |  |
          * Find a method. Attempts to find the most specific applicable method using
81 |  |
          * the algorithm described in the JLS section 15.12.2 (with the exception
82 |  |
          * that it can't distinguish a primitive type argument from an object type
83 |  |
          * argument, since in reflection primitive type arguments are represented by
84 |  |
          * their object counterparts, so for an argument of type (say)
85 |  |
          * java.lang.Integer, it will not be able to decide between a method that
86 |  |
          * takes int and a method that takes java.lang.Integer as a parameter.
87 |  |
          * </p>
88 |  |
          *
89 |  |
          * <p>
90 |  |
          * This turns out to be a relatively rare case where this is needed -
91 |  |
          * however, functionality like this is needed.
92 |  |
          * </p>
93 |  |
          *
94 |  |
          * @param methodName name of method
95 |  |
          * @param args the actual arguments with which the method is called
96 |  |
          * @return the most specific applicable method, or null if no method is
97 |  |
          *         applicable.
98 |  |
          * @throws AmbiguousException if there is more than one maximally specific
99 |  |
          *             applicable method
100 |  |
          */
101 |  |
         public Method find(String methodName, Object[] args) throws AmbiguousException {
102 |  |
             List methodList = get(methodName);
103 |  |
104 |  |
             if (methodList == null) {
105 |  |
                 return null;
106 |  |
             }
107 |  |
108 |  |
             int l = args.length;
109 |  |
             Class[] classes = new Class[l];
110 |  |
111 |  |
             for (int i = 0; i < l; ++i) {
112 |  |
                 Object arg = args[i];
113 |  |
114 |  |
                 /*
115 |  |
                  * if we are careful down below, a null argument goes in there so we
116 |  |
                  * can know that the null was passed to the method
117 |  |
                  */
118 |  |
                 classes[i] = arg == null ? class="keyword">null : arg.getClass();
119 |  |
             }
120 |  |
121 |  |
             return getMostSpecific(methodList, classes);
122 |  |
         }
123 |  |
124 |  |
         /**
125 |  |
          * simple distinguishable exception, used when we run across ambiguous
126 |  |
          * overloading.
127 |  |
          */
128 | 0 |
         public static class AmbiguousException extends Exception {
129 |  |
             /** serialization version id jdk13 generated. */
130 |  |
             static final long serialVersionUID = 8758118091728717367L;
131 |  |
         }
132 |  |
133 |  |
         /**
134 |  |
          * Gets the most specific method from a list.
135 |  |
          * @param methods list of {@link Method methods}
136 |  |
          * @param classes argument types
137 |  |
          * @return the most specific method, or null
138 |  |
          * @throws AmbiguousException if there is more than one specific method
139 |  |
          */
140 |  |
         private static Method getMostSpecific(List methods, Class[] classes) throws AmbiguousException {
141 |  |
             LinkedList applicables = getApplicables(methods, classes);
142 |  |
143 |  |
             if (applicables.isEmpty()) {
144 |  |
                 return null;
145 |  |
             }
146 |  |
147 |  |
             if (applicables.size() == 1) {
148 |  |
                 return (Method) applicables.getFirst();
149 |  |
             }
150 |  |
151 |  |
             /*
152 |  |
              * This list will contain the maximally specific methods. Hopefully at
153 |  |
              * the end of the below loop, the list will contain exactly one method,
154 |  |
              * (the most specific method) otherwise we have ambiguity.
155 |  |
              */
156 |  |
157 |  |
             LinkedList maximals = new LinkedList();
158 |  |
159 |  |
             for (Iterator applicable = applicables.iterator(); applicable.hasNext();) {
160 |  |
                 Method app = (Method) applicable.next();
161 |  |
                 Class[] appArgs = app.getParameterTypes();
162 |  |
                 boolean lessSpecific = false;
163 |  |
164 |  |
                 for (Iterator maximal = maximals.iterator(); !lessSpecific && maximal.hasNext();) {
165 |  |
                     Method max = (Method) maximal.next();
166 |  |
167 |  |
                     switch (moreSpecific(appArgs, max.getParameterTypes())) {
168 |  |
                         case MORE_SPECIFIC:
169 |  |
                             /*
170 |  |
                              * This method is more specific than the previously
171 |  |
                              * known maximally specific, so remove the old maximum.
172 |  |
                              */
173 |  |
                             maximal.remove();
174 |  |
                             break;
175 |  |
176 |  |
                         case LESS_SPECIFIC:
177 |  |
                             /*
178 |  |
                              * This method is less specific than some of the
179 |  |
                              * currently known maximally specific methods, so we
180 |  |
                              * won't add it into the set of maximally specific
181 |  |
                              * methods
182 |  |
                              */
183 |  |
                             lessSpecific = true;
184 |  |
                             break;
185 |  |
                     }
186 |  |
                 }
187 |  |
188 |  |
                 if (!lessSpecclass="keyword">ific) {
189 |  |
                     maximals.addLast(app);
190 |  |
                 }
191 |  |
             }
192 |  |
193 |  |
             if (maximals.size() > 1) {
194 |  |
                 // We have more than one maximally specific method
195 |  |
                 throw new AmbiguousException();
196 |  |
             }
197 |  |
198 |  |
             return (Method) maximals.getFirst();
199 |  |
         }
200 |  |
201 |  |
         /**
202 |  |
          * Determines which method signature (represented by a class array) is more
203 |  |
          * specific. This defines a partial ordering on the method signatures.
204 |  |
          *
205 |  |
          * @param c1 first signature to compare
206 |  |
          * @param c2 second signature to compare
207 |  |
          * @return MORE_SPECIFIC if c1 is more specific than c2, LESS_SPECIFIC if c1
208 |  |
          *         is less specific than c2, INCOMPARABLE if they are incomparable.
209 |  |
          */
210 |  |
         private static int moreSpecific(Class[] c1, Class[] c2) {
211 |  |
             boolean c1MoreSpecific = false;
212 |  |
             boolean c2MoreSpecific = false;
213 |  |
214 |  |
             for (int i = 0; i < c1.length; ++i) {
215 |  |
                 if (c1[i] != c2[i]) {
216 |  |
                     c1MoreSpecific = c1MoreSpecific || isStrictMethodInvocationConvertible(c2[i], c1[i]);
217 |  |
                     c2MoreSpecific = c2MoreSpecific || isStrictMethodInvocationConvertible(c1[i], c2[i]);
218 |  |
                 }
219 |  |
             }
220 |  |
221 |  |
             if (c1MoreSpecclass="keyword">ific) {
222 |  |
                 if (c2MoreSpecclass="keyword">ific) {
223 |  |
                     /*
224 |  |
                      * Incomparable due to cross-assignable arguments (i.e.
225 |  |
                      * foo(String, Object) vs. foo(Object, String))
226 |  |
                      */
227 |  |
228 |  |
                     return INCOMPARABLE;
229 |  |
                 }
230 |  |
231 |  |
                 return MORE_SPECIFIC;
232 |  |
             }
233 |  |
234 |  |
             if (c2MoreSpecclass="keyword">ific) {
235 |  |
                 return LESS_SPECIFIC;
236 |  |
             }
237 |  |
238 |  |
             /*
239 |  |
              * Incomparable due to non-related arguments (i.e. foo(Runnable) vs.
240 |  |
              * foo(Serializable))
241 |  |
              */
242 |  |
243 |  |
             return INCOMPARABLE;
244 |  |
         }
245 |  |
246 |  |
         /**
247 |  |
          * Returns all methods that are applicable to actual argument types.
248 |  |
          *
249 |  |
          * @param methods list of all candidate methods
250 |  |
          * @param classes the actual types of the arguments
251 |  |
          * @return a list that contains only applicable methods (number of formal
252 |  |
          *         and actual arguments matches, and argument types are assignable
253 |  |
          *         to formal types through a method invocation conversion).
254 |  |
          */
255 |  |
         private static LinkedList getApplicables(List methods, Class[] classes) {
256 |  |
             LinkedList list = new LinkedList();
257 |  |
258 |  |
             for (Iterator imethod = methods.iterator(); imethod.hasNext();) {
259 |  |
                 Method method = (Method) imethod.next();
260 |  |
261 |  |
                 if (isApplicable(method, classes)) {
262 |  |
                     list.add(method);
263 |  |
                 }
264 |  |
265 |  |
             }
266 |  |
             return list;
267 |  |
         }
268 |  |
269 |  |
         /**
270 |  |
          * Returns true if the supplied method is applicable to actual argument
271 |  |
          * types.
272 |  |
          * @param method the method to check
273 |  |
          * @param classes possible argument types
274 |  |
          * @return true if the arguments are applicable to the method.
275 |  |
          */
276 |  |
         private static boolean isApplicable(Method method, Class[] classes) {
277 |  |
             Class[] methodArgs = method.getParameterTypes();
278 |  |
279 |  |
             if (methodArgs.length != classes.length) {
280 |  |
                 return false;
281 |  |
             }
282 |  |
283 |  |
             for (int i = 0; i < classes.length; ++i) {
284 |  |
                 if (!isMethodInvocationConvertible(methodArgs[i], classes[i])) {
285 |  |
                     return false;
286 |  |
                 }
287 |  |
             }
288 |  |
289 |  |
             return true;
290 |  |
         }
291 |  |
292 |  |
         /**
293 |  |
          * Determines whether a type represented by a class object is convertible to
294 |  |
          * another type represented by a class object using a method invocation
295 |  |
          * conversion, treating object types of primitive types as if they were
296 |  |
          * primitive types (that is, a Boolean actual parameter type matches boolean
297 |  |
          * primitive formal type). This behavior is because this method is used to
298 |  |
          * determine applicable methods for an actual parameter list, and primitive
299 |  |
          * types are represented by their object duals in reflective method calls.
300 |  |
          *
301 |  |
          * @param formal the formal parameter type to which the actual parameter
302 |  |
          *            type should be convertible
303 |  |
          * @param actual the actual parameter type.
304 |  |
          * @return true if either formal type is assignable from actual type, or
305 |  |
          *         formal is a primitive type and actual is its corresponding object
306 |  |
          *         type or an object type of a primitive type that can be converted
307 |  |
          *         to the formal type.
308 |  |
          */
309 |  |
         private static boolean isMethodInvocationConvertible(Class formal, Class actual) {
310 |  |
             /*
311 |  |
              * if it's a null, it means the arg was null
312 |  |
              */
313 |  |
             if (actual == null && !formal.isPrimitive()) {
314 |  |
                 return true;
315 |  |
             }
316 |  |
317 |  |
             /*
318 |  |
              * Check for identity or widening reference conversion
319 |  |
              */
320 |  |
321 |  |
             if (actual != null && formal.isAssignableFrom(actual)) {
322 |  |
                 return true;
323 |  |
             }
324 |  |
325 |  |
             /*
326 |  |
              * Check for boxing with widening primitive conversion. Note that actual
327 |  |
              * parameters are never primitives.
328 |  |
              */
329 |  |
330 |  |
             if (formal.isPrimitive()) {
331 |  |
                 if (formal == Boolean.TYPE && actual == Boolean.class) {
332 |  |
                     return true;
333 |  |
                 }
334 |  |
                 if (formal == Character.TYPE && actual == Character.class) {
335 |  |
                     return true;
336 |  |
                 }
337 |  |
                 if (formal == Byte.TYPE && actual == Byte.class) {
338 |  |
                     return true;
339 |  |
                 }
340 |  |
                 if (formal == Short.TYPE && (actual == Short.class || actual == Byte.class)) {
341 |  |
                     return true;
342 |  |
                 }
343 |  |
                 if (formal == Integer.TYPE && (actual == Integer.class || actual == Short.class || actual == Byte.class)) {
344 |  |
                     return true;
345 |  |
                 }
346 |  |
                 if (formal == Long.TYPE
347 |  |
                     && (actual == Long.class || actual == Integer.class || actual == Short.class || actual == Byte.class)) {
348 |  |
                     return true;
349 |  |
                 }
350 |  |
                 if (formal == Float.TYPE
351 |  |
                     && (actual == Float.class || actual == Long.class || actual == Integer.class
352 |  |
                         || actual == Short.class || actual == Byte.class)) {
353 |  |
                     return true;
354 |  |
                 }
355 |  |
                 if (formal == Double.TYPE
356 |  |
                     && (actual == Double.class || actual == Float.class || actual == Long.class || actual == Integer.class
357 |  |
                         || actual == Short.class || actual == Byte.class)) {
358 |  |
                     return true;
359 |  |
                 }
360 |  |
             }
361 |  |
362 |  |
             return false;
363 |  |
         }
364 |  |
365 |  |
         /**
366 |  |
          * Determines whether a type represented by a class object is convertible to
367 |  |
          * another type represented by a class object using a method invocation
368 |  |
          * conversion, without matching object and primitive types. This method is
369 |  |
          * used to determine the more specific type when comparing signatures of
370 |  |
          * methods.
371 |  |
          *
372 |  |
          * @param formal the formal parameter type to which the actual parameter
373 |  |
          *            type should be convertible
374 |  |
          * @param actual the actual parameter type.
375 |  |
          * @return true if either formal type is assignable from actual type, or
376 |  |
          *         formal and actual are both primitive types and actual can be
377 |  |
          *         subject to widening conversion to formal.
378 |  |
          */
379 |  |
         private static boolean isStrictMethodInvocationConvertible(Class formal, Class actual) {
380 |  |
             /*
381 |  |
              * we shouldn't get a null into, but if so
382 |  |
              */
383 |  |
             if (actual == null && !formal.isPrimitive()) {
384 |  |
                 return true;
385 |  |
             }
386 |  |
387 |  |
             /*
388 |  |
              * Check for identity or widening reference conversion
389 |  |
              */
390 |  |
391 |  |
             if (formal.isAssignableFrom(actual)) {
392 |  |
                 return true;
393 |  |
             }
394 |  |
395 |  |
             /*
396 |  |
              * Check for widening primitive conversion.
397 |  |
              */
398 |  |
399 |  |
             if (formal.isPrimitive()) {
400 |  |
                 if (formal == Short.TYPE && (actual == Byte.TYPE)) {
401 |  |
                     return true;
402 |  |
                 }
403 |  |
                 if (formal == Integer.TYPE && (actual == Short.TYPE || actual == Byte.TYPE)) {
404 |  |
                     return true;
405 |  |
                 }
406 |  |
                 if (formal == Long.TYPE && (actual == Integer.TYPE || actual == Short.TYPE || actual == Byte.TYPE)) {
407 |  |
                     return true;
408 |  |
                 }
409 |  |
                 if (formal == Float.TYPE
410 |  |
                     && (actual == Long.TYPE || actual == Integer.TYPE || actual == Short.TYPE || actual == Byte.TYPE)) {
411 |  |
                     return true;
412 |  |
                 }
413 |  |
                 if (formal == Double.TYPE
414 |  |
                     && (actual == Float.TYPE || actual == Long.TYPE || actual == Integer.TYPE || actual == Short.TYPE
415 |  |
                         || actual == Byte.TYPE)) {
416 |  |
                     return true;
417 |  |
                 }
418 |  |
             }
419 |  |
             return false;
420 |  |
         }
421 |  |
     }

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