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 * @version $Id: VerifierFactory.java 1749603 2016-06-21 20:50:19Z ggregory $
032 * @see Verifier
033 */
034public class VerifierFactory {
035
036    /**
037     * The HashMap that holds the data about the already-constructed Verifier instances.
038     */
039    private static final Map<String, Verifier> hashMap = new HashMap<>();
040    /**
041     * The VerifierFactoryObserver instances that observe the VerifierFactory.
042     */
043    private static final List<VerifierFactoryObserver> observers = new Vector<>();
044
045
046    /**
047     * The VerifierFactory is not instantiable.
048     */
049    private VerifierFactory() {
050    }
051
052
053    /**
054     * Returns the (only) verifier responsible for the class with the given name.
055     * Possibly a new Verifier object is transparently created.
056     * @return the (only) verifier responsible for the class with the given name.
057     */
058    public static Verifier getVerifier( final String fully_qualified_classname ) {
059        Verifier v = hashMap.get(fully_qualified_classname);
060        if (v == null) {
061            v = new Verifier(fully_qualified_classname);
062            hashMap.put(fully_qualified_classname, v);
063            notify(fully_qualified_classname);
064        }
065        return v;
066    }
067
068
069    /**
070     * Notifies the observers of a newly generated Verifier.
071     */
072    private static void notify( final String fully_qualified_classname ) {
073        // notify the observers
074        for (final VerifierFactoryObserver vfo : observers) {
075            vfo.update(fully_qualified_classname);
076        }
077    }
078
079
080    /**
081     * Returns all Verifier instances created so far.
082     * This is useful when a Verifier recursively lets
083     * the VerifierFactory create other Verifier instances
084     * and if you want to verify the transitive hull of
085     * referenced class files.
086     */
087    public static Verifier[] getVerifiers() {
088        final Verifier[] vs = new Verifier[hashMap.values().size()];
089        return hashMap.values().toArray(vs); // Because vs is big enough, vs is used to store the values into and returned!
090    }
091
092
093    /**
094     * Adds the VerifierFactoryObserver o to the list of observers.
095     */
096    public static void attach( final VerifierFactoryObserver o ) {
097        observers.add(o);
098    }
099
100
101    /**
102     * Removes the VerifierFactoryObserver o from the list of observers.
103     */
104    public static void detach( final VerifierFactoryObserver o ) {
105        observers.remove(o);
106    }
107}