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.RuntimeLogger;
25 import org.apache.velocity.runtime.log.Log;
26 import org.apache.velocity.runtime.log.RuntimeLoggerLog;
27
28 /**
29 * This basic function of this class is to return a Method
30 * object for a particular class given the name of a method
31 * and the parameters to the method in the form of an Object[]
32 *
33 * The first time the Introspector sees a
34 * class it creates a class method map for the
35 * class in question. Basically the class method map
36 * is a Hastable where Method objects are keyed by a
37 * concatenation of the method name and the names of
38 * classes that make up the parameters.
39 *
40 * For example, a method with the following signature:
41 *
42 * public void method(String a, StringBuffer b)
43 *
44 * would be mapped by the key:
45 *
46 * "method" + "java.lang.String" + "java.lang.StringBuffer"
47 *
48 * This mapping is performed for all the methods in a class
49 * and stored for
50 * @author <a href="mailto:jvanzyl@apache.org">Jason van Zyl</a>
51 * @author <a href="mailto:bob@werken.com">Bob McWhirter</a>
52 * @author <a href="mailto:szegedia@freemail.hu">Attila Szegedi</a>
53 * @author <a href="mailto:paulo.gaspar@krankikom.de">Paulo Gaspar</a>
54 * @author <a href="mailto:henning@apache.org">Henning P. Schmiedehausen</a>
55 * @version $Id: Introspector.java 477003 2006-11-20 01:14:22Z henning $
56 */
57 public class Introspector extends IntrospectorBase
58 {
59 /**
60 * define a public string so that it can be looked for
61 * if interested
62 */
63
64 public final static String CACHEDUMP_MSG =
65 "Introspector: detected classloader change. Dumping cache.";
66
67 /**
68 * @param log A Log object to use for the introspector.
69 */
70 public Introspector(final Log log)
71 {
72 super(log);
73 }
74
75 /**
76 * @param logger A runtime logger object.
77 * @deprecated RuntimeLogger is deprecated. Use Introspector(Log log).
78 */
79 public Introspector(final RuntimeLogger logger)
80 {
81 this(new RuntimeLoggerLog(logger));
82 }
83
84 /**
85 * Gets the method defined by <code>name</code> and
86 * <code>params</code> for the Class <code>c</code>.
87 *
88 * @param c Class in which the method search is taking place
89 * @param name Name of the method being searched for
90 * @param params An array of Objects (not Classes) that describe the
91 * the parameters
92 *
93 * @return The desired Method object.
94 * @throws IllegalArgumentException When the parameters passed in can not be used for introspection.
95 */
96 public Method getMethod(final Class c, final String name, final Object[] params)
97 throws IllegalArgumentException
98 {
99 try
100 {
101 return super.getMethod(c, name, params);
102 }
103 catch(MethodMap.AmbiguousException ae)
104 {
105 /*
106 * whoops. Ambiguous. Make a nice log message and return null...
107 */
108
109 StringBuffer msg = new StringBuffer("Introspection Error : Ambiguous method invocation ")
110 .append(name)
111 .append("(");
112
113 for (int i = 0; i < params.length; i++)
114 {
115 if (i > 0)
116 {
117 msg.append(", ");
118 }
119
120 if (params[i] == null)
121 {
122 msg.append("null");
123 }
124 else
125 {
126 msg.append(params[i].getClass().getName());
127 }
128 }
129
130 msg.append(") for class ")
131 .append(c);
132
133 log.error(msg.toString());
134 }
135
136 return null;
137 }
138
139 /**
140 * Logs that the Introspector Cache has been cleared.
141 */
142 public void triggerClear()
143 {
144 super.triggerClear();
145 log.info(CACHEDUMP_MSG);
146 }
147 }