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Java > Open Source Codes > org > apache > velocity > util > introspection > Introspector


1 package org.apache.velocity.util.introspection;
2
3 /*
4  * Copyright 2001,2004 The Apache Software Foundation.
5  *
6  * Licensed under the Apache License, Version 2.0 (the "License");
7  * you may not use this file except in compliance with the License.
8  * You may obtain a copy of the License at
9  *
10  * http://www.apache.org/licenses/LICENSE-2.0
11  *
12  * Unless required by applicable law or agreed to in writing, software
13  * distributed under the License is distributed on an "AS IS" BASIS,
14  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15  * See the License for the specific language governing permissions and
16  * limitations under the License.
17  */
18
19 import java.util.Map JavaDoc;
20 import java.util.Set JavaDoc;
21 import java.util.HashMap JavaDoc;
22 import java.util.HashSet JavaDoc;
23
24 import java.lang.reflect.Method JavaDoc;
25
26 import org.apache.velocity.runtime.RuntimeServices;
27 import org.apache.velocity.runtime.RuntimeLogger;
28
29 /**
30  * This basic function of this class is to return a Method
31  * object for a particular class given the name of a method
32  * and the parameters to the method in the form of an Object[]
33  *
34  * The first time the Introspector sees a
35  * class it creates a class method map for the
36  * class in question. Basically the class method map
37  * is a Hastable where Method objects are keyed by a
38  * concatenation of the method name and the names of
39  * classes that make up the parameters.
40  *
41  * For example, a method with the following signature:
42  *
43  * public void method(String a, StringBuffer b)
44  *
45  * would be mapped by the key:
46  *
47  * "method" + "java.lang.String" + "java.lang.StringBuffer"
48  *
49  * This mapping is performed for all the methods in a class
50  * and stored for
51  * @author <a HREF="mailto:jvanzyl@apache.org">Jason van Zyl</a>
52  * @author <a HREF="mailto:bob@werken.com">Bob McWhirter</a>
53  * @author <a HREF="mailto:szegedia@freemail.hu">Attila Szegedi</a>
54  * @author <a HREF="mailto:paulo.gaspar@krankikom.de">Paulo Gaspar</a>
55  * @version $Id: Introspector.java,v 1.21.4.1 2004/03/03 23:23:08 geirm Exp $
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 JavaDoc CACHEDUMP_MSG =
65         "Introspector : detected classloader change. Dumping cache.";
66
67     /**
68      * our engine runtime services
69      */
70     private RuntimeLogger rlog = null;
71
72     /**
73      * Recieves our RuntimeServices object
74      */
75     public Introspector(RuntimeLogger logger)
76     {
77         this.rlog = logger;
78     }
79    
80     /**
81      * Gets the method defined by <code>name</code> and
82      * <code>params</code> for the Class <code>c</code>.
83      *
84      * @param c Class in which the method search is taking place
85      * @param name Name of the method being searched for
86      * @param params An array of Objects (not Classes) that describe the
87      * the parameters
88      *
89      * @return The desired Method object.
90      */
91     public Method JavaDoc getMethod(Class JavaDoc c, String JavaDoc name, Object JavaDoc[] params)
92         throws Exception JavaDoc
93     {
94         /*
95          * just delegate to the base class
96          */
97
98         try
99         {
100             return super.getMethod( c, name, params );
101         }
102         catch( MethodMap.AmbiguousException ae )
103         {
104             /*
105              * whoops. Ambiguous. Make a nice log message and return null...
106              */
107
108             String JavaDoc msg = "Introspection Error : Ambiguous method invocation "
109                 + name + "( ";
110
111             for (int i = 0; i < params.length; i++)
112             {
113                 if ( i > 0)
114                     msg = msg + ", ";
115                 
116                 msg = msg + params[i].getClass().getName();
117             }
118             
119             msg = msg + ") for class " + c;
120             
121             rlog.error( msg );
122         }
123
124         return null;
125     }
126
127     /**
128      * Clears the classmap and classname
129      * caches, and logs that we did so
130      */
131     protected void clearCache()
132     {
133         super.clearCache();
134         rlog.info( CACHEDUMP_MSG );
135     }
136 }
137
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