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