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 477003 2006-11-20 01:14:22Z henning $
53 */
54 public abstract class IntrospectorBase
55 implements IntrospectorCacheListener
56 {
57 /** Class logger */
58 protected final Log log;
59
60 /** The Introspector Cache */
61 private final IntrospectorCache introspectorCache;
62
63 /**
64 * C'tor.
65 */
66 protected IntrospectorBase(final Log log)
67 {
68 this.log = log;
69 introspectorCache = new IntrospectorCacheImpl(log); // TODO: Load that from properties.
70 introspectorCache.addListener(this);
71 }
72
73 /**
74 * Gets the method defined by <code>name</code> and
75 * <code>params</code> for the Class <code>c</code>.
76 *
77 * @param c Class in which the method search is taking place
78 * @param name Name of the method being searched for
79 * @param params An array of Objects (not Classes) that describe the
80 * the parameters
81 *
82 * @return The desired Method object.
83 * @throws IllegalArgumentException When the parameters passed in can not be used for introspection.
84 * @throws MethodMap.AmbiguousException When the method map contains more than one match for the requested signature.
85 */
86 public Method getMethod(final Class c, final String name, final Object[] params)
87 throws IllegalArgumentException,MethodMap.AmbiguousException
88 {
89 if (c == null)
90 {
91 throw new IllegalArgumentException ("class object is null!");
92 }
93
94 if (params == null)
95 {
96 throw new IllegalArgumentException("params object is null!");
97 }
98
99 ClassMap classMap = null;
100
101 IntrospectorCache ic = getIntrospectorCache();
102
103 synchronized(ic)
104 {
105 classMap = ic.get(c);
106
107 if (classMap == null)
108 {
109 classMap = ic.put(c);
110 }
111 }
112
113 return classMap.findMethod(name, params);
114 }
115
116 /**
117 * Return the internal IntrospectorCache object.
118 *
119 * @return The internal IntrospectorCache object.
120 */
121 protected IntrospectorCache getIntrospectorCache()
122 {
123 return introspectorCache;
124 }
125
126 /**
127 * Clears the internal cache.
128 *
129 * @deprecated Use getIntrospectorCache().clear();
130 */
131 protected void clearCache()
132 {
133 getIntrospectorCache().clear();
134 }
135
136 /**
137 * Creates a class map for specific class and registers it in the
138 * cache. Also adds the qualified name to the name->class map
139 * for later Classloader change detection.
140 *
141 * @param c The class for which the class map gets generated.
142 * @return A ClassMap object.
143 *
144 * @deprecated Use getIntrospectorCache().put(c);
145 */
146 protected ClassMap createClassMap(final Class c)
147 {
148 return getIntrospectorCache().put(c);
149 }
150
151 /**
152 * Lookup a given Class object in the cache. If it does not exist,
153 * check whether this is due to a class change and purge the caches
154 * eventually.
155 *
156 * @param c The class to look up.
157 * @return A ClassMap object or null if it does not exist in the cache.
158 *
159 * @deprecated Use getIntrospectorCache().get(c);
160 */
161 protected ClassMap lookupClassMap(final Class c)
162 {
163 return getIntrospectorCache().get(c);
164 }
165
166 /**
167 * @see IntrospectorCacheListener#triggerClear()
168 */
169 public void triggerClear()
170 {
171 }
172
173 /**
174 * @see IntrospectorCacheListener#triggerGet(Class, ClassMap)
175 */
176 public void triggerGet(Class c, ClassMap classMap)
177 {
178 }
179
180 /**
181 * @see IntrospectorCacheListener#triggerPut(Class, ClassMap)
182 */
183 public void triggerPut(Class c, ClassMap classMap)
184 {
185 }
186 }