    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.util;
    019
    020import java.util.LinkedHashMap;
    021import java.util.Map;
    022
    023import org.apache.bcel.classfile.JavaClass;
    024
    025/**
    026 * Maintains a least-recently-used (LRU) cache of {@link JavaClass} with maximum size {@code cacheSize}.
    027 *
    028 * <p>
    029 * This repository supports a class path consisting of too many JAR files to handle in {@link ClassPathRepository} or
    030 * {@link MemorySensitiveClassPathRepository} without causing {@code OutOfMemoryError}.
    031 * </p>
    032 *
    033 * @since 6.4.0
    034 */
    035public class LruCacheClassPathRepository extends AbstractClassPathRepository {
    036
    037    private final LinkedHashMap<String, JavaClass> loadedClasses;
    038
    039    public LruCacheClassPathRepository(final ClassPath path, final int cacheSize) {
    040        super(path);
    041
    042        if (cacheSize < 1) {
    043            throw new IllegalArgumentException("cacheSize must be a positive number.");
    044        }
    045        final int initialCapacity = (int) (0.75 * cacheSize);
    046        final boolean accessOrder = true; // Evicts least-recently-accessed
    047        loadedClasses = new LinkedHashMap<String, JavaClass>(initialCapacity, cacheSize, accessOrder) {
    048
    049            private static final long serialVersionUID = 1L;
    050
    051            @Override
    052            protected boolean removeEldestEntry(final Map.Entry<String, JavaClass> eldest) {
    053                return size() > cacheSize;
    054            }
    055        };
    056    }
    057
    058    @Override
    059    public JavaClass findClass(final String className) {
    060        return loadedClasses.get(className);
    061    }
    062
    063    @Override
    064    public void storeClass(final JavaClass javaClass) {
    065        // Not storing parent's _loadedClass
    066        loadedClasses.put(javaClass.getClassName(), javaClass);
    067        javaClass.setRepository(this);
    068    }
    069
    070    @Override
    071    public void removeClass(final JavaClass javaClass) {
    072        loadedClasses.remove(javaClass.getClassName());
    073    }
    074
    075    @Override
    076    public void clear() {
    077        loadedClasses.clear();
    078    }
    079}