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.util;
020
021import java.util.LinkedHashMap;
022import java.util.Map;
023
024import org.apache.bcel.classfile.JavaClass;
025
026/**
027 * Maintains a least-recently-used (LRU) cache of {@link JavaClass} with maximum size {@code cacheSize}.
028 *
029 * <p>
030 * This repository supports a class path consisting of too many JAR files to handle in {@link ClassPathRepository} or
031 * {@link MemorySensitiveClassPathRepository} without causing {@code OutOfMemoryError}.
032 * </p>
033 *
034 * @since 6.4.0
035 */
036public class LruCacheClassPathRepository extends AbstractClassPathRepository {
037
038    private final LinkedHashMap<String, JavaClass> loadedClasses;
039
040    /**
041     * Constructs a new LruCacheClassPathRepository.
042     *
043     * @param path The class path.
044     * @param cacheSize The cache size.
045     */
046    public LruCacheClassPathRepository(final ClassPath path, final int cacheSize) {
047        super(path);
048
049        if (cacheSize < 1) {
050            throw new IllegalArgumentException("cacheSize must be a positive number.");
051        }
052        final int initialCapacity = (int) (0.75 * cacheSize);
053        final boolean accessOrder = true; // Evicts least-recently-accessed
054        loadedClasses = new LinkedHashMap<String, JavaClass>(initialCapacity, cacheSize, accessOrder) {
055
056            private static final long serialVersionUID = 1L;
057
058            @Override
059            protected boolean removeEldestEntry(final Map.Entry<String, JavaClass> eldest) {
060                return size() > cacheSize;
061            }
062        };
063    }
064
065    @Override
066    public void clear() {
067        loadedClasses.clear();
068    }
069
070    @Override
071    public JavaClass findClass(final String className) {
072        return loadedClasses.get(className);
073    }
074
075    @Override
076    public void removeClass(final JavaClass javaClass) {
077        loadedClasses.remove(javaClass.getClassName());
078    }
079
080    @Override
081    public void storeClass(final JavaClass javaClass) {
082        // Not storing parent's _loadedClass
083        loadedClasses.put(javaClass.getClassName(), javaClass);
084        javaClass.setRepository(this);
085    }
086}