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| org.apache.commons.jexl.util.introspection.IntrospectorBase | 
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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.util.Map; | |
| 20 |  import java.util.Set; | |
| 21 |  import java.util.HashMap; | |
| 22 |  import java.util.HashSet; | |
| 23 | ||
| 24 |  import java.lang.reflect.Method; | |
| 25 | ||
| 26 |  /** | |
| 27 |   * This basic function of this class is to return a Method object for a | |
| 28 |   * particular class given the name of a method and the parameters to the method | |
| 29 |   * in the form of an Object[] | |
| 30 |   *  | |
| 31 |   * The first time the Introspector sees a class it creates a class method map | |
| 32 |   * for the class in question. Basically the class method map is a Hastable where | |
| 33 |   * Method objects are keyed by a concatenation of the method name and the names | |
| 34 |   * of classes that make up the parameters. | |
| 35 |   *  | |
| 36 |   * For example, a method with the following signature: | |
| 37 |   *  | |
| 38 |   * public void method(String a, StringBuffer b) | |
| 39 |   *  | |
| 40 |   * would be mapped by the key: | |
| 41 |   *  | |
| 42 |   * "method" + "java.lang.String" + "java.lang.StringBuffer" | |
| 43 |   *  | |
| 44 |   * This mapping is performed for all the methods in a class and stored for | |
| 45 |   *  | |
| 46 |   * @since 1.0 | |
| 47 |   * @author <a href="mailto:jvanzyl@apache.org">Jason van Zyl</a> | |
| 48 |   * @author <a href="mailto:bob@werken.com">Bob McWhirter</a> | |
| 49 |   * @author <a href="mailto:szegedia@freemail.hu">Attila Szegedi</a> | |
| 50 |   * @author <a href="mailto:paulo.gaspar@krankikom.de">Paulo Gaspar</a> | |
| 51 |   * @version $Id: IntrospectorBase.java 398464 2006-04-30 23:50:43Z dion $ | |
| 52 |   */ | |
| 53 | 8 | public class IntrospectorBase { | 
| 54 |      /** | |
| 55 |       * Holds the method maps for the classes we know about, keyed by Class | |
| 56 |       * object. | |
| 57 |       */ | |
| 58 | 4 | protected Map classMethodMaps = new HashMap(); | 
| 59 | ||
| 60 |      /** | |
| 61 |       * Holds the qualified class names for the classes we hold in the | |
| 62 |       * classMethodMaps hash. | |
| 63 |       */ | |
| 64 | 4 | protected Set cachedClassNames = new HashSet(); | 
| 65 | ||
| 66 |      /** | |
| 67 |       * Gets the method defined by <code>name</code> and <code>params</code> | |
| 68 |       * for the Class <code>c</code>. | |
| 69 |       *  | |
| 70 |       * @param c Class in which the method search is taking place | |
| 71 |       * @param name Name of the method being searched for | |
| 72 |       * @param params An array of Objects (not Classes) that describe the the | |
| 73 |       *            parameters | |
| 74 |       *  | |
| 75 |       * @return The desired Method object. | |
| 76 |       * @throws Exception on any logical error. | |
| 77 |       */ | |
| 78 |      public Method getMethod(Class c, String name, Object[] params) throws Exception { | |
| 79 | 98 | if (c == null) { | 
| 80 | 0 |              throw new Exception("Introspector.getMethod(): Class method key was null: " + name); | 
| 81 | } | |
| 82 | ||
| 83 | 98 |          ClassMap classMap = null; | 
| 84 | ||
| 85 | 98 |          synchronized (classMethodMaps) { | 
| 86 | 98 | classMap = (ClassMap) classMethodMaps.get(c); | 
| 87 | ||
| 88 |              /* | |
| 89 |               * if we don't have this, check to see if we have it by name. if so, | |
| 90 |               * then we have a classloader change so dump our caches. | |
| 91 |               */ | |
| 92 | ||
| 93 | 98 | if (classMap == null) { | 
| 94 | 10 |                  if (cachedClassNames.contains(c.getName())) { | 
| 95 |                      /* | |
| 96 |                       * we have a map for a class with same name, but not this | |
| 97 |                       * class we are looking at. This implies a classloader | |
| 98 |                       * change, so dump | |
| 99 |                       */ | |
| 100 | 0 |                      clearCache(); | 
| 101 | } | |
| 102 | ||
| 103 | 10 | classMap = createClassMap(c); | 
| 104 | } | |
| 105 | 98 | } | 
| 106 | ||
| 107 | 98 |          return classMap.findMethod(name, params); | 
| 108 | } | |
| 109 | ||
| 110 |      /** | |
| 111 |       * Creates a class map for specific class and registers it in the cache. | |
| 112 |       * Also adds the qualified name to the name->class map for later Classloader | |
| 113 |       * change detection. | |
| 114 |       * @param c class. | |
| 115 |       * @return a {@link ClassMap} | |
| 116 |       */ | |
| 117 |      protected ClassMap createClassMap(Class c) { | |
| 118 | 10 |          ClassMap classMap = new ClassMap(c); | 
| 119 | 10 | classMethodMaps.put(c, classMap); | 
| 120 | 10 | cachedClassNames.add(c.getName()); | 
| 121 | ||
| 122 | 10 |          return classMap; | 
| 123 | } | |
| 124 | ||
| 125 |      /** | |
| 126 |       * Clears the classmap and classname caches. | |
| 127 |       */ | |
| 128 | protected void clearCache() { | |
| 129 |          /* | |
| 130 |           * since we are synchronizing on this object, we have to clear it rather | |
| 131 |           * than just dump it. | |
| 132 |           */ | |
| 133 | 0 |          classMethodMaps.clear(); | 
| 134 | ||
| 135 |          /* | |
| 136 |           * for speed, we can just make a new one and let the old one be GC'd | |
| 137 |           */ | |
| 138 | 0 |          cachedClassNames = new HashSet(); | 
| 139 | 0 |      } | 
| 140 | } | 
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