    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.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}