    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one
    003 * or more contributor license agreements.  See the NOTICE file
    004 * distributed with this work for additional information
    005 * regarding copyright ownership.  The ASF licenses this file
    006 * to you under the Apache License, Version 2.0 (the
    007 * "License"); you may not use this file except in compliance
    008 * with the License.  You may obtain a copy of the License at
    009 *
    010 *   https://www.apache.org/licenses/LICENSE-2.0
    011 *
    012 * Unless required by applicable law or agreed to in writing,
    013 * software distributed under the License is distributed on an
    014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
    015 * KIND, either express or implied.  See the License for the
    016 * specific language governing permissions and limitations
    017 * under the License.
    018 */
    019package org.apache.bcel.verifier;
    020
    021import java.util.HashMap;
    022import java.util.List;
    023import java.util.Map;
    024import java.util.Vector;
    025
    026/**
    027 * This class produces instances of the Verifier class. Its purpose is to make sure that they are singleton instances
    028 * with respect to the class name they 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> MAP = new HashMap<>();
    039
    040    /**
    041     * The VerifierFactoryObserver instances that observe the VerifierFactory.
    042     */
    043    private static final List<VerifierFactoryObserver> OBSVERVERS = new Vector<>();
    044
    045    /**
    046     * Adds the VerifierFactoryObserver o to the list of observers.
    047     */
    048    public static void attach(final VerifierFactoryObserver o) {
    049        OBSVERVERS.add(o);
    050    }
    051
    052    /**
    053     * Clears the factory.
    054     *
    055     * @since 6.6.2
    056     */
    057    public static void clear() {
    058        MAP.clear();
    059        OBSVERVERS.clear();
    060    }
    061
    062    /**
    063     * Removes the VerifierFactoryObserver o from the list of observers.
    064     */
    065    public static void detach(final VerifierFactoryObserver o) {
    066        OBSVERVERS.remove(o);
    067    }
    068
    069    /**
    070     * Returns the (only) verifier responsible for the class with the given name. Possibly a new Verifier object is
    071     * transparently created.
    072     *
    073     * @return the (only) verifier responsible for the class with the given name.
    074     */
    075    public static Verifier getVerifier(final String fullyQualifiedClassName) {
    076        return MAP.computeIfAbsent(fullyQualifiedClassName, k -> {
    077            final Verifier v = new Verifier(k);
    078            notify(k);
    079            return v;
    080        });
    081    }
    082
    083    /**
    084     * Returns all Verifier instances created so far. This is useful when a Verifier recursively lets the VerifierFactory
    085     * create other Verifier instances and if you want to verify the transitive hull of referenced class files.
    086     */
    087    public static Verifier[] getVerifiers() {
    088        return MAP.values().toArray(Verifier.EMPTY_ARRAY);
    089    }
    090
    091    /**
    092     * Notifies the observers of a newly generated Verifier.
    093     */
    094    private static void notify(final String fullyQualifiedClassName) {
    095        // notify the observers
    096        OBSVERVERS.forEach(vfo -> vfo.update(fullyQualifiedClassName));
    097    }
    098
    099    /**
    100     * The VerifierFactory is not instantiable.
    101     */
    102    private VerifierFactory() {
    103    }
    104}