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1   /*
2    * Copyright 2001,2004 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;
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 Hastable 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   * @author <a href="mailto:jvanzyl@apache.org">Jason van Zyl</a>
47   * @author <a href="mailto:bob@werken.com">Bob McWhirter</a>
48   * @author <a href="mailto:szegedia@freemail.hu">Attila Szegedi</a>
49   * @author <a href="mailto:paulo.gaspar@krankikom.de">Paulo Gaspar</a>
50   * @version $Id: Introspector.java,v 1.6 2004/08/23 13:50:00 dion Exp $
51   */
52  public class Introspector extends IntrospectorBase
53  {
54      /***
55       *  define a public string so that it can be looked for
56       *  if interested
57       */
58  
59      public static final String CACHEDUMP_MSG = 
60          "Introspector : detected classloader change. Dumping cache.";
61  
62      /***
63       *  our engine runtime services
64       */
65      private  Log rlog = null;
66  
67      /***
68       *  Recieves our RuntimeServices object
69       */
70      public Introspector(Log logger)
71      {
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       */
86      public Method getMethod(Class c, String name, Object[] params)
87          throws Exception
88      {
89          /*
90           *  just delegate to the base class
91           */
92  
93          try
94          {
95              return super.getMethod( c, name, params );
96          }
97          catch( MethodMap.AmbiguousException ae )
98          {
99              /*
100              *  whoops.  Ambiguous.  Make a nice log message and return null...
101              */
102 
103             String msg = "Introspection Error : Ambiguous method invocation "
104                 + name + "( ";
105 
106             for (int i = 0; i < params.length; i++)
107             {
108                 if ( i > 0)
109                     msg += ", ";
110                 
111                 msg += params[i].getClass().getName();
112             }
113             
114             msg = msg + ") for class " + c;
115             
116             rlog.error( msg );
117         }
118 
119         return null;
120     }
121 
122     /***
123      * Clears the classmap and classname
124      * caches, and logs that we did so
125      */
126     protected void clearCache()
127     {
128         super.clearCache();
129         rlog.info( CACHEDUMP_MSG );
130     }
131 }