| 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.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 |
| 28 | * object for a particular class given the name of a method |
| 29 | * and the parameters to the method in the form of an Object[] |
| 30 | * |
| 31 | * The first time the Introspector sees a |
| 32 | * class it creates a class method map for the |
| 33 | * class in question. Basically the class method map |
| 34 | * is a Hastable where Method objects are keyed by a |
| 35 | * concatenation of the method name and the names of |
| 36 | * classes that make up the parameters. |
| 37 | * |
| 38 | * For example, a method with the following signature: |
| 39 | * |
| 40 | * public void method(String a, StringBuffer b) |
| 41 | * |
| 42 | * would be mapped by the key: |
| 43 | * |
| 44 | * "method" + "java.lang.String" + "java.lang.StringBuffer" |
| 45 | * |
| 46 | * This mapping is performed for all the methods in a class |
| 47 | * and stored for |
| 48 | * @author <a href="mailto:jvanzyl@apache.org">Jason van Zyl</a> |
| 49 | * @author <a href="mailto:bob@werken.com">Bob McWhirter</a> |
| 50 | * @author <a href="mailto:szegedia@freemail.hu">Attila Szegedi</a> |
| 51 | * @author <a href="mailto:paulo.gaspar@krankikom.de">Paulo Gaspar</a> |
| 52 | * @version $Id: IntrospectorBase.java,v 1.2.8.1 2004/03/03 23:23:08 geirm Exp $ |
| 53 | */ |
| 54 | public class IntrospectorBase |
| 55 | { |
| 56 | /** |
| 57 | * Holds the method maps for the classes we know about, keyed by |
| 58 | * Class object. |
| 59 | */ |
| 60 | protected Map classMethodMaps = new HashMap(); |
| 61 | |
| 62 | /** |
| 63 | * Holds the qualified class names for the classes |
| 64 | * we hold in the classMethodMaps hash |
| 65 | */ |
| 66 | protected Set cachedClassNames = new HashSet(); |
| 67 | |
| 68 | /** |
| 69 | * Gets the method defined by <code>name</code> and |
| 70 | * <code>params</code> for the Class <code>c</code>. |
| 71 | * |
| 72 | * @param c Class in which the method search is taking place |
| 73 | * @param name Name of the method being searched for |
| 74 | * @param params An array of Objects (not Classes) that describe the |
| 75 | * the parameters |
| 76 | * |
| 77 | * @return The desired Method object. |
| 78 | */ |
| 79 | public Method getMethod(Class c, String name, Object[] params) |
| 80 | throws Exception |
| 81 | { |
| 82 | if (c == null) |
| 83 | { |
| 84 | throw new Exception ( |
| 85 | "Introspector.getMethod(): Class method key was null: " + name ); |
| 86 | } |
| 87 | |
| 88 | ClassMap classMap = null; |
| 89 | |
| 90 | synchronized(classMethodMaps) |
| 91 | { |
| 92 | classMap = (ClassMap)classMethodMaps.get(c); |
| 93 | |
| 94 | /* |
| 95 | * if we don't have this, check to see if we have it |
| 96 | * by name. if so, then we have a classloader change |
| 97 | * so dump our caches. |
| 98 | */ |
| 99 | |
| 100 | if (classMap == null) |
| 101 | { |
| 102 | if ( cachedClassNames.contains( c.getName() )) |
| 103 | { |
| 104 | /* |
| 105 | * we have a map for a class with same name, but not |
| 106 | * this class we are looking at. This implies a |
| 107 | * classloader change, so dump |
| 108 | */ |
| 109 | clearCache(); |
| 110 | } |
| 111 | |
| 112 | classMap = createClassMap(c); |
| 113 | } |
| 114 | } |
| 115 | |
| 116 | return classMap.findMethod(name, params); |
| 117 | } |
| 118 | |
| 119 | /** |
| 120 | * Creates a class map for specific class and registers it in the |
| 121 | * cache. Also adds the qualified name to the name->class map |
| 122 | * for later Classloader change detection. |
| 123 | */ |
| 124 | protected ClassMap createClassMap(Class c) |
| 125 | { |
| 126 | ClassMap classMap = new ClassMap( c ); |
| 127 | classMethodMaps.put(c, classMap); |
| 128 | cachedClassNames.add( c.getName() ); |
| 129 | |
| 130 | return classMap; |
| 131 | } |
| 132 | |
| 133 | /** |
| 134 | * Clears the classmap and classname |
| 135 | * caches |
| 136 | */ |
| 137 | protected void clearCache() |
| 138 | { |
| 139 | /* |
| 140 | * since we are synchronizing on this |
| 141 | * object, we have to clear it rather than |
| 142 | * just dump it. |
| 143 | */ |
| 144 | classMethodMaps.clear(); |
| 145 | |
| 146 | /* |
| 147 | * for speed, we can just make a new one |
| 148 | * and let the old one be GC'd |
| 149 | */ |
| 150 | cachedClassNames = new HashSet(); |
| 151 | } |
| 152 | } |