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Java > Open Source Codes > org > springframework > beans > factory > access > BeanFactoryBootstrap


1 /*
2  * Copyright 2002-2005 the original author or authors.
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.springframework.beans.factory.access;
18
19 import org.springframework.beans.BeansException;
20 import org.springframework.beans.factory.BeanFactory;
21 import org.springframework.beans.factory.NoSuchBeanDefinitionException;
22 import org.springframework.beans.factory.support.DefaultListableBeanFactory;
23 import org.springframework.beans.factory.support.PropertiesBeanDefinitionReader;
24 import org.springframework.util.Assert;
25
26 /**
27  * One singleton to rule them all. Reads System properties, which
28  * must contain the definition of a bootstrap bean factory using
29  * the Properties syntax supported by PropertiesBeanDefinitionReader.
30  *
31  * <p>The name of the bootstrap factory must be "bootstrapBeanFactory".
32  * Thus a typical definition might be:
33  *
34  * <pre>
35  * bootstrapBeanFactory.class=com.mycompany.MyBeanFactory</pre>
36  *
37  * Use as follows:
38  *
39  * <pre>
40  * BeanFactory bf = BeanFactoryBootstrap.getInstance().getBeanFactory();</pre>
41  *
42  * @author Rod Johnson
43  * @since 02.12.2002
44  * @see org.springframework.beans.factory.support.PropertiesBeanDefinitionReader
45  */
46 public class BeanFactoryBootstrap {
47     
48     public static final String JavaDoc BEAN_FACTORY_BEAN_NAME = "bootstrapBeanFactory";
49
50     private static BeanFactoryBootstrap instance;
51     
52     private static BeansException startupException;
53     
54     private static void initializeSingleton() {
55         try {
56             instance = new BeanFactoryBootstrap();
57         }
58         catch (BeansException ex) {
59             startupException = ex;
60         }
61     }
62     
63     // Do initialization when this class is loaded to avoid
64 // potential concurrency issues or the need to synchronize later
65 static {
66         initializeSingleton();
67     }
68
69     /**
70      * Return the singleton instance of the bootstrap factory
71      * @return BeanFactoryBootstrap
72      * @throws org.springframework.beans.BeansException
73      */
74     public static BeanFactoryBootstrap getInstance() throws BeansException {
75         if (startupException != null) {
76             throw startupException;
77         }
78         Assert.notNull(instance);
79         return instance;
80     }
81     
82     /**
83      * <b>For testing only. Cleans and reinitalizes the instance.
84      * Do not use in a production application!</b>
85      */
86     protected static void reinitialize() {
87         instance = null;
88         startupException = null;
89         initializeSingleton();
90     }
91
92
93     /** the singleton instance */
94     private BeanFactory bootstrapFactory;
95     
96     /**
97      * Apply rules to load factory.
98      */
99     private BeanFactoryBootstrap() throws BeansException {
100         DefaultListableBeanFactory startupFactory = new DefaultListableBeanFactory();
101         PropertiesBeanDefinitionReader propReader = new PropertiesBeanDefinitionReader(startupFactory);
102         try {
103             propReader.registerBeanDefinitions(System.getProperties());
104             this.bootstrapFactory = (BeanFactory) startupFactory.getBean(BEAN_FACTORY_BEAN_NAME, BeanFactory.class);
105         }
106         catch (NoSuchBeanDefinitionException ex) {
107             throw new BootstrapException(
108                     "No bean named '" + BEAN_FACTORY_BEAN_NAME + "' in system properties: [" + startupFactory + "]");
109         }
110         catch (BeansException ex) {
111             throw new BootstrapException("Failed to bootstrap bean factory", ex);
112         }
113     }
114
115     /**
116      * Return the BeanFactory managed by the Bootstrap.
117      */
118     public BeanFactory getBeanFactory() {
119         return bootstrapFactory;
120     }
121     
122 }
123
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