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    1   /*
    2    * Copyright  2000-2004 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.bcel.verifier;
    18
    19  import java.util.HashMap;
    20  import java.util.Iterator;
    21  import java.util.List;
    22  import java.util.Map;
    23  import java.util.Vector;
    24
    25  /***
    26   * This class produces instances of the Verifier class. Its purpose is to make
    27   * sure that they are singleton instances with respect to the class name they
    28   * operate on. That means, for every class (represented by a unique fully qualified
    29   * class name) there is exactly one Verifier.
    30   *
    31   * @version $Id: VerifierFactory.java 386056 2006-03-15 11:31:56Z tcurdt $
    32   * @author Enver Haase
    33   * @see org.apache.bcel.verifier.Verifier
    34   */
    35  public class VerifierFactory {
    36
    37      /***
    38       * The HashMap that holds the data about the already-constructed Verifier instances.
    39       */
    40      private static Map hashMap = new HashMap();
    41      /***
    42       * The VerifierFactoryObserver instances that observe the VerifierFactory.
    43       */
    44      private static List observers = new Vector();
    45
    46
    47      /***
    48       * The VerifierFactory is not instantiable.
    49       */
    50      private VerifierFactory() {
    51      }
    52
    53
    54      /***
    55       * Returns the (only) verifier responsible for the class with the given name.
    56       * Possibly a new Verifier object is transparently created.
    57       * @return the (only) verifier responsible for the class with the given name.
    58       */
    59      public static Verifier getVerifier( String fully_qualified_classname ) {
    60          Verifier v = (Verifier) (hashMap.get(fully_qualified_classname));
    61          if (v == null) {
    62              v = new Verifier(fully_qualified_classname);
    63              hashMap.put(fully_qualified_classname, v);
    64              notify(fully_qualified_classname);
    65          }
    66          return v;
    67      }
    68
    69
    70      /***
    71       * Notifies the observers of a newly generated Verifier.
    72       */
    73      private static void notify( String fully_qualified_classname ) {
    74          // notify the observers
    75          Iterator i = observers.iterator();
    76          while (i.hasNext()) {
    77              VerifierFactoryObserver vfo = (VerifierFactoryObserver) i.next();
    78              vfo.update(fully_qualified_classname);
    79          }
    80      }
    81
    82
    83      /***
    84       * Returns all Verifier instances created so far.
    85       * This is useful when a Verifier recursively lets
    86       * the VerifierFactory create other Verifier instances
    87       * and if you want to verify the transitive hull of
    88       * referenced class files.
    89       */
    90      public static Verifier[] getVerifiers() {
    91          Verifier[] vs = new Verifier[hashMap.values().size()];
    92          return (Verifier[]) (hashMap.values().toArray(vs)); // Because vs is big enough, vs is used to store the values into and returned!
    93      }
    94
    95
    96      /***
    97       * Adds the VerifierFactoryObserver o to the list of observers.
    98       */
    99      public static void attach( VerifierFactoryObserver o ) {
    100         observers.add(o);
    101     }
    102
    103
    104     /***
    105      * Removes the VerifierFactoryObserver o from the list of observers.
    106      */
    107     public static void detach( VerifierFactoryObserver o ) {
    108         observers.remove(o);
    109     }
    110 }