1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing,
13 * software distributed under the License is distributed on an
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15 * KIND, either express or implied. See the License for the
16 * specific language governing permissions and limitations
17 * under the License.
18 */
19 package org.apache.shiro.util;
20
21 /**
22 * TODO - Class JavaDoc
23 *
24 * @since 1.0
25 */
26 public abstract class AbstractFactory<T> implements Factory<T> {
27
28 private boolean singleton;
29 private T singletonInstance;
30
31 public AbstractFactory() {
32 this.singleton = true;
33 }
34
35 public boolean isSingleton() {
36 return singleton;
37 }
38
39 public void setSingleton(boolean singleton) {
40 this.singleton = singleton;
41 }
42
43 public T getInstance() {
44 T instance;
45 if (isSingleton()) {
46 if (this.singletonInstance == null) {
47 this.singletonInstance = createInstance();
48 }
49 instance = this.singletonInstance;
50 } else {
51 instance = createInstance();
52 }
53 if (instance == null) {
54 String msg = "Factory 'createInstance' implementation returned a null object.";
55 throw new IllegalStateException(msg);
56 }
57 return instance;
58 }
59
60 protected abstract T createInstance();
61 }