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Java > Open Source Codes > org > apache > commons > jexl > util > introspection > Introspector


1 /*
2  * Copyright 2001-2006 The Apache Software Foundation.
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16
17 package org.apache.commons.jexl.util.introspection;
18
19 import java.lang.reflect.Method JavaDoc;
20
21 import org.apache.commons.logging.Log;
22
23
24 /**
25  * This basic function of this class is to return a Method
26  * object for a particular class given the name of a method
27  * and the parameters to the method in the form of an Object[]
28  *
29  * The first time the Introspector sees a
30  * class it creates a class method map for the
31  * class in question. Basically the class method map
32  * is a Hashtable where Method objects are keyed by a
33  * concatenation of the method name and the names of
34  * classes that make up the parameters.
35  *
36  * For example, a method with the following signature:
37  *
38  * public void method(String a, StringBuffer b)
39  *
40  * would be mapped by the key:
41  *
42  * "method" + "java.lang.String" + "java.lang.StringBuffer"
43  *
44  * This mapping is performed for all the methods in a class
45  * and stored for
46  * @since 1.0
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  * @version $Id: Introspector.java 398171 2006-04-29 14:57:29Z dion $
52  */
53 public class Introspector extends IntrospectorBase {
54     /**
55      * define a public string so that it can be looked for
56      * if interested.
57      */
58
59     public static final String JavaDoc CACHEDUMP_MSG =
60         "Introspector : detected classloader change. Dumping cache.";
61
62     /**
63      * our engine runtime services.
64      */
65     private final Log rlog;
66
67     /**
68      * Recieves our RuntimeServices object.
69      * @param logger a {@link Log}.
70      */
71     public Introspector(Log logger) {
72         this.rlog = logger;
73     }
74    
75     /**
76      * Gets the method defined by <code>name</code> and
77      * <code>params</code> for the Class <code>c</code>.
78      *
79      * @param c Class in which the method search is taking place
80      * @param name Name of the method being searched for
81      * @param params An array of Objects (not Classes) that describe the
82      * the parameters
83      *
84      * @return The desired Method object.
85      * @throws Exception if the superclass does.
86      */
87     public Method JavaDoc getMethod(Class JavaDoc c, String JavaDoc name, Object JavaDoc[] params) throws Exception JavaDoc {
88         /*
89          * just delegate to the base class
90          */
91
92         try {
93             return super.getMethod(c, name, params);
94         } catch (MethodMap.AmbiguousException ae) {
95             /*
96              * whoops. Ambiguous. Make a nice log message and return null...
97              */
98
99             StringBuffer JavaDoc msg = new StringBuffer JavaDoc("Introspection Error : Ambiguous method invocation ")
100                 .append(name).append("( ");
101
102             for (int i = 0; i < params.length; i++) {
103                 if (i > 0) {
104                     msg.append(", ");
105                 }
106                 
107                 msg.append(params[i].getClass().getName());
108             }
109             
110             msg.append(") for class ").append(c.getName());
111             
112             rlog.error(msg.toString());
113         }
114
115         return null;
116     }
117
118     /**
119      * Clears the classmap and classname
120      * caches, and logs that we did so.
121      */
122     protected void clearCache() {
123         super.clearCache();
124         rlog.info(CACHEDUMP_MSG);
125     }
126 }
127
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