| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, |
| * software distributed under the License is distributed on an |
| * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| * KIND, either express or implied. See the License for the |
| * specific language governing permissions and limitations |
| * under the License. |
| */ |
| |
| package freemarker.cache; |
| |
| import java.lang.ref.Reference; |
| import java.lang.ref.ReferenceQueue; |
| import java.lang.ref.SoftReference; |
| import java.lang.reflect.InvocationTargetException; |
| import java.lang.reflect.Method; |
| import java.util.Map; |
| import java.util.concurrent.ConcurrentHashMap; |
| import java.util.concurrent.ConcurrentMap; |
| |
| import freemarker.template.utility.UndeclaredThrowableException; |
| |
| /** |
| * Soft cache storage is a cache storage that uses {@link SoftReference} objects to hold the objects it was passed, |
| * therefore allows the garbage collector to purge the cache when it determines that it wants to free up memory. This |
| * class is thread-safe to the extent that its underlying map is. The parameterless constructor uses a thread-safe map |
| * since 2.3.24 or Java 5. |
| * |
| * @see freemarker.template.Configuration#setCacheStorage(CacheStorage) |
| */ |
| public class SoftCacheStorage implements ConcurrentCacheStorage, CacheStorageWithGetSize { |
| private static final Method atomicRemove = getAtomicRemoveMethod(); |
| |
| private final ReferenceQueue queue = new ReferenceQueue(); |
| private final Map map; |
| private final boolean concurrent; |
| |
| /** |
| * Creates an instance that uses a {@link ConcurrentMap} internally. |
| */ |
| public SoftCacheStorage() { |
| this(new ConcurrentHashMap()); |
| } |
| |
| /** |
| * Returns true if the underlying Map is a {@code ConcurrentMap}. |
| */ |
| public boolean isConcurrent() { |
| return concurrent; |
| } |
| |
| public SoftCacheStorage(Map backingMap) { |
| map = backingMap; |
| this.concurrent = map instanceof ConcurrentMap; |
| } |
| |
| public Object get(Object key) { |
| processQueue(); |
| Reference ref = (Reference) map.get(key); |
| return ref == null ? null : ref.get(); |
| } |
| |
| public void put(Object key, Object value) { |
| processQueue(); |
| map.put(key, new SoftValueReference(key, value, queue)); |
| } |
| |
| public void remove(Object key) { |
| processQueue(); |
| map.remove(key); |
| } |
| |
| public void clear() { |
| map.clear(); |
| processQueue(); |
| } |
| |
| /** |
| * Returns a close approximation of the number of cache entries. |
| * |
| * @since 2.3.21 |
| */ |
| public int getSize() { |
| processQueue(); |
| return map.size(); |
| } |
| |
| private void processQueue() { |
| for (; ; ) { |
| SoftValueReference ref = (SoftValueReference) queue.poll(); |
| if (ref == null) { |
| return; |
| } |
| Object key = ref.getKey(); |
| if (concurrent) { |
| try { |
| atomicRemove.invoke(map, new Object[] { key, ref }); |
| } catch (IllegalAccessException | InvocationTargetException e) { |
| throw new UndeclaredThrowableException(e); |
| } |
| } else if (map.get(key) == ref) { |
| map.remove(key); |
| } |
| } |
| } |
| |
| private static final class SoftValueReference extends SoftReference { |
| private final Object key; |
| |
| SoftValueReference(Object key, Object value, ReferenceQueue queue) { |
| super(value, queue); |
| this.key = key; |
| } |
| |
| Object getKey() { |
| return key; |
| } |
| } |
| |
| private static Method getAtomicRemoveMethod() { |
| try { |
| return Class.forName("java.util.concurrent.ConcurrentMap").getMethod("remove", new Class[] { Object.class, Object.class }); |
| } catch (ClassNotFoundException e) { |
| return null; |
| } catch (NoSuchMethodException e) { |
| throw new UndeclaredThrowableException(e); |
| } |
| } |
| } |