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 org.slf4j.Logger; 20 import org.slf4j.LoggerFactory; 21 22 /** 23 * An abstract Template design pattern implementation of {@link SingletonFactory}. 24 * 25 * @param <Input> the factory input class type 26 * @param <Output> the factory output class type 27 */ 28 public abstract class AbstractSingletonFactory<Input, Output> implements SingletonFactory<Input, Output> { 29 30 /** Class logger. */ 31 private final Logger log = LoggerFactory.getLogger(AbstractSingletonFactory.class); 32 33 /** {@inheritDoc} */ 34 public synchronized Output getInstance(Input input) { 35 Output output = get(input); 36 if (output != null) { 37 log.trace("Input key mapped to a non-null value, returning output"); 38 return output; 39 } else { 40 log.trace("Input key mapped to a null value"); 41 } 42 43 log.trace("Creating new output instance and inserting to factory map"); 44 output = createNewInstance(input); 45 if (output == null) { 46 log.error("New output instance was not created"); 47 return null; 48 } 49 50 put(input, output); 51 52 return output; 53 } 54 55 /** 56 * Get the output instance currently associated with 57 * the input instance. 58 * 59 * @param input the input instance key 60 * @return the output instance which corresponds to the input instance, 61 * or null if not present 62 */ 63 protected abstract Output get(Input input); 64 65 /** 66 * Store the input and output instance association. 67 * 68 * @param input the input instance key 69 * @param output the output instance value 70 */ 71 protected abstract void put(Input input, Output output); 72 73 /** 74 * Create a new instance of the output class based on the input 75 * class instance. 76 * 77 * @param input the input class instance 78 * @return an output class instance 79 */ 80 protected abstract Output createNewInstance(Input input); 81 82 }