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 }