/**
* 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 org.apache.mahout.cf.taste.web;
import org.apache.mahout.cf.taste.recommender.Recommender;
import org.apache.mahout.common.ClassUtils;
/**
* <p>A singleton which holds an instance of a {@link Recommender}. This is used to share
* a {@link Recommender} between {@link RecommenderServlet} and {@code RecommenderService.jws}.</p>
*/
public final class RecommenderSingleton {
private final Recommender recommender;
private static RecommenderSingleton instance;
public static synchronized RecommenderSingleton getInstance() {
if (instance == null) {
throw new IllegalStateException("Not initialized");
}
return instance;
}
public static synchronized void initializeIfNeeded(String recommenderClassName) {
if (instance == null) {
instance = new RecommenderSingleton(recommenderClassName);
}
}
private RecommenderSingleton(String recommenderClassName) {
if (recommenderClassName == null) {
throw new IllegalArgumentException("Recommender class name is null");
}
recommender = ClassUtils.instantiateAs(recommenderClassName, Recommender.class);
}
public Recommender getRecommender() {
return recommender;
}
}