1 /* 2 * Copyright [2007] [University Corporation for Advanced Internet Development, Inc.] 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package org.opensaml.xml.util; 18 19 import java.util.WeakHashMap; 20 21 /** 22 * A simple implementation of {@link SingletonFactory}. 23 * 24 * <p> 25 * A {@link WeakHashMap} is used as the underlying store. This ensures that if the input class 26 * instance become otherwise unused (weakly reachable), the input class instance key used 27 * within the factory will not prevent the input class instance from being garbage-collected, 28 * thereby preventing a memory leak. 29 * </p> 30 * 31 * <p> 32 * <strong>NOTE: </strong>If the output class instance holds a strong or soft reference to the input class, 33 * do not use this factory. See instead {@link AbstractWrappedSingletonFactory}. Usage of this 34 * class in that scenario will result in a memory leak, as the input class instance will never 35 * become weakly reachable and therefore never garbage collected. 36 * </p> 37 * 38 * 39 * @param <Input> the factory input class type 40 * @param <Output> the factory output class type 41 */ 42 public abstract class AbstractSimpleSingletonFactory<Input, Output> 43 extends AbstractSingletonFactory<Input, Output> { 44 45 /** Storage for the factory. */ 46 private WeakHashMap<Input, Output> map; 47 48 /** Constructor. */ 49 public AbstractSimpleSingletonFactory() { 50 map = new WeakHashMap<Input, Output>(); 51 } 52 53 /** {@inheritDoc} */ 54 protected synchronized Output get(Input input) { 55 return map.get(input); 56 } 57 58 /** {@inheritDoc} */ 59 protected synchronized void put(Input input, Output output) { 60 map.put(input, output); 61 } 62 63 }