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Java > Open Source Codes > org > apache > bcel > verifier > VerifierFactory


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 JavaDoc;
20 import java.util.Iterator JavaDoc;
21 import java.util.List JavaDoc;
22 import java.util.Map JavaDoc;
23 import java.util.Vector JavaDoc;
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 JavaDoc hashMap = new HashMap JavaDoc();
41     /**
42      * The VerifierFactoryObserver instances that observe the VerifierFactory.
43      */
44     private static List JavaDoc observers = new Vector JavaDoc();
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 JavaDoc 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 JavaDoc fully_qualified_classname ) {
74         // notify the observers
75 Iterator JavaDoc 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 }
111
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