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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 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 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 getMethod(Class c, String name, Object[] params) throws Exception {
88
89
90
91
92 try {
93 return super.getMethod(c, name, params);
94 } catch (MethodMap.AmbiguousException ae) {
95
96
97
98
99 StringBuffer msg = new StringBuffer("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 }