001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 *  Unless required by applicable law or agreed to in writing, software
012 *  distributed under the License is distributed on an "AS IS" BASIS,
013 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 *  See the License for the specific language governing permissions and
015 *  limitations under the License.
016 *
017 */
018package org.apache.bcel.verifier;
019
020import java.util.HashMap;
021import java.util.List;
022import java.util.Map;
023import java.util.Vector;
024
025/**
026 * This class produces instances of the Verifier class. Its purpose is to make
027 * sure that they are singleton instances with respect to the class name they
028 * operate on. That means, for every class (represented by a unique fully qualified
029 * class name) there is exactly one Verifier.
030 *
031 * @see Verifier
032 */
033public class VerifierFactory {
034
035    /**
036     * The HashMap that holds the data about the already-constructed Verifier instances.
037     */
038    private static final Map<String, Verifier> hashMap = new HashMap<>();
039    /**
040     * The VerifierFactoryObserver instances that observe the VerifierFactory.
041     */
042    private static final List<VerifierFactoryObserver> observers = new Vector<>();
043
044
045    /**
046     * The VerifierFactory is not instantiable.
047     */
048    private VerifierFactory() {
049    }
050
051
052    /**
053     * Returns the (only) verifier responsible for the class with the given name.
054     * Possibly a new Verifier object is transparently created.
055     * @return the (only) verifier responsible for the class with the given name.
056     */
057    public static Verifier getVerifier( final String fullyQualifiedClassName ) {
058        Verifier v = hashMap.get(fullyQualifiedClassName);
059        if (v == null) {
060            v = new Verifier(fullyQualifiedClassName);
061            hashMap.put(fullyQualifiedClassName, v);
062            notify(fullyQualifiedClassName);
063        }
064        return v;
065    }
066
067
068    /**
069     * Notifies the observers of a newly generated Verifier.
070     */
071    private static void notify( final String fullyQualifiedClassName ) {
072        // notify the observers
073        for (final VerifierFactoryObserver vfo : observers) {
074            vfo.update(fullyQualifiedClassName);
075        }
076    }
077
078
079    /**
080     * Returns all Verifier instances created so far.
081     * This is useful when a Verifier recursively lets
082     * the VerifierFactory create other Verifier instances
083     * and if you want to verify the transitive hull of
084     * referenced class files.
085     */
086    public static Verifier[] getVerifiers() {
087        final Verifier[] vs = new Verifier[hashMap.values().size()];
088        return hashMap.values().toArray(vs); // Because vs is big enough, vs is used to store the values into and returned!
089    }
090
091
092    /**
093     * Adds the VerifierFactoryObserver o to the list of observers.
094     */
095    public static void attach( final VerifierFactoryObserver o ) {
096        observers.add(o);
097    }
098
099
100    /**
101     * Removes the VerifierFactoryObserver o from the list of observers.
102     */
103    public static void detach( final VerifierFactoryObserver o ) {
104        observers.remove(o);
105    }
106}