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    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;
    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           *  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 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 }