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.Field;
23 import java.lang.reflect.Method;
24
25 import org.apache.velocity.runtime.log.Log;
26
27 /**
28 * Lookup a a Method object for a particular class given the name of a method
29 * and its parameters.
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 Hashtable 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 * @author <a href="mailto:henning@apache.org">Henning P. Schmiedehausen</a>
53 * @author <a href="mailto:cdauth@cdauth.eu">Candid Dauth</a>
54 * @version $Id: IntrospectorBase.java 1329799 2012-04-24 15:41:21Z cbrisson $
55 */
56 public abstract class IntrospectorBase
57 {
58 /** Class logger */
59 protected final Log log;
60
61 /** The Introspector Cache */
62 private final IntrospectorCache introspectorCache;
63
64 /**
65 * C'tor.
66 */
67 protected IntrospectorBase(final Log log)
68 {
69 this.log = log;
70 introspectorCache = new IntrospectorCacheImpl(log); // TODO: Load that from properties.
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 IntrospectorCache ic = getIntrospectorCache();
100
101 ClassMap classMap = ic.get(c);
102 if (classMap == null)
103 {
104 classMap = ic.put(c);
105 }
106
107 return classMap.findMethod(name, params);
108 }
109
110 /**
111 * Gets the field defined by <code>name</code>.
112 *
113 * @param c Class in which the method search is taking place
114 * @param name Name of the field being searched for
115 *
116 * @return The desired Field object.
117 * @throws IllegalArgumentException When the parameters passed in can not be used for introspection.
118 */
119 public Field getField(final Class c, final String name)
120 throws IllegalArgumentException
121 {
122 if (c == null)
123 {
124 throw new IllegalArgumentException("class object is null!");
125 }
126
127 IntrospectorCache ic = getIntrospectorCache();
128
129 ClassFieldMap classFieldMap = ic.getFieldMap(c);
130 if (classFieldMap == null)
131 {
132 ic.put(c);
133 classFieldMap = ic.getFieldMap(c);
134 }
135
136 return classFieldMap.findField(name);
137 }
138
139 /**
140 * Return the internal IntrospectorCache object.
141 *
142 * @return The internal IntrospectorCache object.
143 * @since 1.5
144 */
145 protected IntrospectorCache getIntrospectorCache()
146 {
147 return introspectorCache;
148 }
149
150 }