    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 */
    017package org.apache.bcel.util;
    018
    019import java.util.LinkedHashMap;
    020import java.util.Map;
    021
    022import org.apache.bcel.classfile.JavaClass;
    023
    024/**
    025 * Maintains a least-recently-used (LRU) cache of {@link JavaClass} with maximum size {@code cacheSize}.
    026 *
    027 * <p>
    028 * This repository supports a class path consisting of too many JAR files to handle in {@link ClassPathRepository} or
    029 * {@link MemorySensitiveClassPathRepository} without causing {@code OutOfMemoryError}.
    030 * </p>
    031 *
    032 * @since 6.4.0
    033 */
    034public class LruCacheClassPathRepository extends AbstractClassPathRepository {
    035
    036    private final LinkedHashMap<String, JavaClass> loadedClasses;
    037
    038    public LruCacheClassPathRepository(final ClassPath path, final int cacheSize) {
    039        super(path);
    040
    041        if (cacheSize < 1) {
    042            throw new IllegalArgumentException("cacheSize must be a positive number.");
    043        }
    044        final int initialCapacity = (int) (0.75 * cacheSize);
    045        final boolean accessOrder = true; // Evicts least-recently-accessed
    046        loadedClasses = new LinkedHashMap<String, JavaClass>(initialCapacity, cacheSize, accessOrder) {
    047
    048            private static final long serialVersionUID = 1L;
    049
    050            @Override
    051            protected boolean removeEldestEntry(final Map.Entry<String, JavaClass> eldest) {
    052                return size() > cacheSize;
    053            }
    054        };
    055    }
    056
    057    @Override
    058    public void clear() {
    059        loadedClasses.clear();
    060    }
    061
    062    @Override
    063    public JavaClass findClass(final String className) {
    064        return loadedClasses.get(className);
    065    }
    066
    067    @Override
    068    public void removeClass(final JavaClass javaClass) {
    069        loadedClasses.remove(javaClass.getClassName());
    070    }
    071
    072    @Override
    073    public void storeClass(final JavaClass javaClass) {
    074        // Not storing parent's _loadedClass
    075        loadedClasses.put(javaClass.getClassName(), javaClass);
    076        javaClass.setRepository(this);
    077    }
    078}