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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 }