1 package org.apache.velocity.util.introspection; 2 3 /* 4 * Licensed to the Apache Software Foundation (ASF) under one 5 * or more contributor license agreements. See the NOTICE file 6 * distributed with this work for additional information 7 * regarding copyright ownership. The ASF licenses this file 8 * to you under the Apache License, Version 2.0 (the 9 * "License"); you may not use this file except in compliance 10 * with the License. You may obtain a copy of the License at 11 * 12 * http://www.apache.org/licenses/LICENSE-2.0 13 * 14 * Unless required by applicable law or agreed to in writing, 15 * software distributed under the License is distributed on an 16 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 17 * KIND, either express or implied. See the License for the 18 * specific language governing permissions and limitations 19 * under the License. 20 */ 21 22 import java.lang.reflect.Method; 23 24 import org.apache.velocity.runtime.log.Log; 25 26 /** 27 * Lookup a a Method object for a particular class given the name of a method 28 * and its parameters. 29 * 30 * The first time the Introspector sees a 31 * class it creates a class method map for the 32 * class in question. Basically the class method map 33 * is a Hashtable where Method objects are keyed by a 34 * concatenation of the method name and the names of 35 * classes that make up the parameters. 36 * 37 * For example, a method with the following signature: 38 * 39 * public void method(String a, StringBuffer b) 40 * 41 * would be mapped by the key: 42 * 43 * "method" + "java.lang.String" + "java.lang.StringBuffer" 44 * 45 * This mapping is performed for all the methods in a class 46 * and stored for. 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 * @author <a href="mailto:henning@apache.org">Henning P. Schmiedehausen</a> 52 * @version $Id: IntrospectorBase.java 685685 2008-08-13 21:43:27Z nbubna $ 53 */ 54 public abstract class IntrospectorBase 55 { 56 /** Class logger */ 57 protected final Log log; 58 59 /** The Introspector Cache */ 60 private final IntrospectorCache introspectorCache; 61 62 /** 63 * C'tor. 64 */ 65 protected IntrospectorBase(final Log log) 66 { 67 this.log = log; 68 introspectorCache = new IntrospectorCacheImpl(log); // TODO: Load that from properties. 69 } 70 71 /** 72 * Gets the method defined by <code>name</code> and 73 * <code>params</code> for the Class <code>c</code>. 74 * 75 * @param c Class in which the method search is taking place 76 * @param name Name of the method being searched for 77 * @param params An array of Objects (not Classes) that describe the 78 * the parameters 79 * 80 * @return The desired Method object. 81 * @throws IllegalArgumentException When the parameters passed in can not be used for introspection. 82 * @throws MethodMap.AmbiguousException When the method map contains more than one match for the requested signature. 83 */ 84 public Method getMethod(final Class c, final String name, final Object[] params) 85 throws IllegalArgumentException,MethodMap.AmbiguousException 86 { 87 if (c == null) 88 { 89 throw new IllegalArgumentException ("class object is null!"); 90 } 91 92 if (params == null) 93 { 94 throw new IllegalArgumentException("params object is null!"); 95 } 96 97 IntrospectorCache ic = getIntrospectorCache(); 98 99 ClassMap classMap = ic.get(c); 100 if (classMap == null) 101 { 102 classMap = ic.put(c); 103 } 104 105 return classMap.findMethod(name, params); 106 } 107 108 /** 109 * Return the internal IntrospectorCache object. 110 * 111 * @return The internal IntrospectorCache object. 112 * @since 1.5 113 */ 114 protected IntrospectorCache getIntrospectorCache() 115 { 116 return introspectorCache; 117 } 118 119 }