1   package org.apache.bcel.verifier;
2   
3   /* ====================================================================
4    * The Apache Software License, Version 1.1
5    *
6    * Copyright (c) 2001 The Apache Software Foundation.  All rights
7    * reserved.
8    *
9    * Redistribution and use in source and binary forms, with or without
10   * modification, are permitted provided that the following conditions
11   * are met:
12   *
13   * 1. Redistributions of source code must retain the above copyright
14   *    notice, this list of conditions and the following disclaimer.
15   *
16   * 2. Redistributions in binary form must reproduce the above copyright
17   *    notice, this list of conditions and the following disclaimer in
18   *    the documentation and/or other materials provided with the
19   *    distribution.
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21   * 3. The end-user documentation included with the redistribution,
22   *    if any, must include the following acknowledgment:
23   *       "This product includes software developed by the
24   *        Apache Software Foundation (http://www.apache.org/)."
25   *    Alternately, this acknowledgment may appear in the software itself,
26   *    if and wherever such third-party acknowledgments normally appear.
27   *
28   * 4. The names "Apache" and "Apache Software Foundation" and
29   *    "Apache BCEL" must not be used to endorse or promote products
30   *    derived from this software without prior written permission. For
31   *    written permission, please contact apache@apache.org.
32   *
33   * 5. Products derived from this software may not be called "Apache",
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35   *    prior written permission of the Apache Software Foundation.
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50   *
51   * This software consists of voluntary contributions made by many
52   * individuals on behalf of the Apache Software Foundation.  For more
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54   * <http://www.apache.org/>.
55   */
56  
57  import java.util.HashMap;
58  import java.util.Iterator;
59  import java.util.Vector;
60  
61  /***
62   * This class produces instances of the Verifier class. Its purpose is to make
63   * sure that they are singleton instances with respect to the class name they
64   * operate on. That means, for every class (represented by a unique fully qualified
65   * class name) there is exactly one Verifier.
66   *
67   * @version $Id: VerifierFactory.java,v 1.2 2002/02/07 23:22:30 enver Exp $
68   * @author <A HREF="http://www.inf.fu-berlin.de/~ehaase"/>Enver Haase</A>
69   * @see org.apache.bcel.verifier.Verifier
70   */
71  public class VerifierFactory{
72  
73  	/***
74  	 * The HashMap that holds the data about the already-constructed Verifier instances.
75  	 */
76  	private static HashMap hashMap = new HashMap();
77  
78  	/***
79  	 * The VerifierFactoryObserver instances that observe the VerifierFactory.
80  	 */
81  	private static Vector observers = new Vector();
82  
83  	/***
84  	 * The VerifierFactory is not instantiable.
85  	 */
86  	private VerifierFactory(){}
87  	
88  	/***
89  	 * Returns the (only) verifier responsible for the class with the given name.
90  	 * Possibly a new Verifier object is transparently created.
91  	 * @return the (only) verifier responsible for the class with the given name.
92  	 */
93  	public static Verifier getVerifier(String fully_qualified_classname){
94  		fully_qualified_classname = fully_qualified_classname;
95  		
96  		Verifier v = (Verifier) (hashMap.get(fully_qualified_classname));
97  		if (v==null){
98  			v = new Verifier(fully_qualified_classname);
99  			hashMap.put(fully_qualified_classname, v);
100 			notify(fully_qualified_classname);
101 		}
102 		
103 		return v;
104 	}
105 
106 	/***
107 	 * Notifies the observers of a newly generated Verifier.
108 	 */
109 	private static void notify(String fully_qualified_classname){
110 		// notify the observers
111 		Iterator i = observers.iterator();
112 		while (i.hasNext()){
113 			VerifierFactoryObserver vfo = (VerifierFactoryObserver) i.next();
114 			vfo.update(fully_qualified_classname);
115 		}
116 	}
117 
118 	/***
119 	 * Returns all Verifier instances created so far.
120 	 * This is useful when a Verifier recursively lets
121 	 * the VerifierFactory create other Verifier instances
122 	 * and if you want to verify the transitive hull of
123 	 * referenced class files.
124 	 */
125 	public static Verifier[] getVerifiers(){
126 		Verifier[] vs = new Verifier[hashMap.values().size()];
127 		return (Verifier[]) (hashMap.values().toArray(vs));	// Because vs is big enough, vs is used to store the values into and returned!
128 	}
129 
130 	/***
131 	 * Adds the VerifierFactoryObserver o to the list of observers.
132 	 */
133 	public static void attach(VerifierFactoryObserver o){
134 		observers.addElement(o);
135 	}
136 	
137 	/***
138 	 * Removes the VerifierFactoryObserver o from the list of observers.
139 	 */
140 	public static void detach(VerifierFactoryObserver o){
141 			observers.removeElement(o);
142 	}
143 }
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