001/*
002 * Copyright 2002-2016 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.core.type.classreading;
018
019import java.io.IOException;
020import java.util.LinkedHashMap;
021import java.util.Map;
022
023import org.springframework.core.io.Resource;
024import org.springframework.core.io.ResourceLoader;
025
026/**
027 * Caching implementation of the {@link MetadataReaderFactory} interface,
028 * caching a {@link MetadataReader} instance per Spring {@link Resource} handle
029 * (i.e. per ".class" file).
030 *
031 * @author Juergen Hoeller
032 * @author Costin Leau
033 * @since 2.5
034 */
035public class CachingMetadataReaderFactory extends SimpleMetadataReaderFactory {
036
037        /** Default maximum number of entries for the MetadataReader cache: 256 */
038        public static final int DEFAULT_CACHE_LIMIT = 256;
039
040
041        private volatile int cacheLimit = DEFAULT_CACHE_LIMIT;
042
043        @SuppressWarnings("serial")
044        private final Map<Resource, MetadataReader> metadataReaderCache =
045                        new LinkedHashMap<Resource, MetadataReader>(DEFAULT_CACHE_LIMIT, 0.75f, true) {
046                                @Override
047                                protected boolean removeEldestEntry(Map.Entry<Resource, MetadataReader> eldest) {
048                                        return size() > getCacheLimit();
049                                }
050                        };
051
052
053        /**
054         * Create a new CachingMetadataReaderFactory for the default class loader.
055         */
056        public CachingMetadataReaderFactory() {
057                super();
058        }
059
060        /**
061         * Create a new CachingMetadataReaderFactory for the given resource loader.
062         * @param resourceLoader the Spring ResourceLoader to use
063         * (also determines the ClassLoader to use)
064         */
065        public CachingMetadataReaderFactory(ResourceLoader resourceLoader) {
066                super(resourceLoader);
067        }
068
069        /**
070         * Create a new CachingMetadataReaderFactory for the given class loader.
071         * @param classLoader the ClassLoader to use
072         */
073        public CachingMetadataReaderFactory(ClassLoader classLoader) {
074                super(classLoader);
075        }
076
077
078        /**
079         * Specify the maximum number of entries for the MetadataReader cache.
080         * <p>Default is 256.
081         */
082        public void setCacheLimit(int cacheLimit) {
083                this.cacheLimit = cacheLimit;
084        }
085
086        /**
087         * Return the maximum number of entries for the MetadataReader cache.
088         */
089        public int getCacheLimit() {
090                return this.cacheLimit;
091        }
092
093
094        @Override
095        public MetadataReader getMetadataReader(Resource resource) throws IOException {
096                if (getCacheLimit() <= 0) {
097                        return super.getMetadataReader(resource);
098                }
099                synchronized (this.metadataReaderCache) {
100                        MetadataReader metadataReader = this.metadataReaderCache.get(resource);
101                        if (metadataReader == null) {
102                                metadataReader = super.getMetadataReader(resource);
103                                this.metadataReaderCache.put(resource, metadataReader);
104                        }
105                        return metadataReader;
106                }
107        }
108
109        /**
110         * Clear the entire MetadataReader cache, removing all cached class metadata.
111         */
112        public void clearCache() {
113                synchronized (this.metadataReaderCache) {
114                        this.metadataReaderCache.clear();
115                }
116        }
117
118}