Spring原理（1）——容器

容器接口


BeanFactory

• 是ApplicationContext的父接口，所有ApplicationContext的实现都组合了BeanFactory。
  
• BeanFactory才是Spring的核心容器。
  

从BeanFactory提供的方法来看，主要是从容器中获取Bean。实际上控制反转，依赖注入以及Bean的生命周期管理，都由它的实现类提供。如下展示了BeanFactory其中一个实现类DefaultListableBeanFactory的继承关系。

可以看到，它的继承路线上有一个DefaultSingletonBeanRegistry类，这个类我们打开可以看到如下代码段，其中singletonObjects对象正是容器中所有单例对象被保存的地方。

1. public class DefaultSingletonBeanRegistry extends SimpleAliasRegistry implements SingletonBeanRegistry {
2.         /** Cache of singleton objects: bean name to bean instance. */
3.         private final Map<String, Object> singletonObjects = new ConcurrentHashMap<>(256);  // 保存了所有的单例对象
5.         /** Cache of singleton factories: bean name to ObjectFactory. */
6.         private final Map<String, ObjectFactory<?>> singletonFactories = new HashMap<>(16);
7.        
8.         ...
9. }

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通常我们会使用如下方式来启动和加载Spring容器

1. @SpringBootApplication
2. public class SsmpApplication {
4.     public static void main(String[] args) throws IOException {
5.         final ConfigurableApplicationContext context = SpringApplication.run(SsmpApplication.class, args);
7.         // MessageSource接口提供的功能，实现国际化能力
8.         context.getMessage("hi", null, Locale.CHINA);
9.         context.getMessage("hi", null, Locale.US);
11.         // ResourcePatternResolver接口提供的能力，实现读取资源文件的能力
12.         final Resource[] resources = context.getResources("classpath*:spring.factories");
14.         // EnvironmentCapable接口提供的能力，实现获取环境参数的能力，可以获取环境变量、配置等
15.         final String java_home = context.getEnvironment().getProperty("java_home");
16.         final String port = context.getEnvironment().getProperty("server.port");
18.         // ApplicationEventPublisher提供的能力，可以发送事件，实现解耦
19.         context.publishEvent(new MyEvent(context));
20.     }
22.     public static class MyEvent extends ApplicationEvent {
24.         public MyEvent(Object source) {
25. package com.leo.domain;
27. import lombok.Data;
29. @Data
30. public class Book {
31.     private Integer id;
33.     private String type;
35.     private String name;
37.     private String description;
38. }super(source);
39.         }
40.     }
41. }

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其内部实现如果简单的拆开来，可以用如下步骤表示，BeanFactory是真正的容器，我们使用XmlBeanDefinitionReader将xml中定义的bean转化成BeanDefinition并注册到BeanFactory中。

1. package com.leo.ssmp;
3. import lombok.extern.slf4j.Slf4j;
5. import org.springframework.beans.factory.annotation.Autowired;
6. import org.springframework.beans.factory.config.BeanDefinition;
7. import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
8. import org.springframework.beans.factory.config.BeanPostProcessor;
9. import org.springframework.beans.factory.support.BeanDefinitionBuilder;
10. import org.springframework.beans.factory.support.DefaultListableBeanFactory;
11. import org.springframework.boot.autoconfigure.SpringBootApplication;
12. import org.springframework.context.annotation.AnnotationConfigUtils;
13. import org.springframework.context.annotation.Bean;
14. import org.springframework.context.annotation.Configuration;
16. import java.util.Collection;
18. @SpringBootApplication
19. @Slf4j
20. public class SsmpApplication {
22.     public static void main(String[] args) {
23.         // 将MyConfig类注册到BeanFactory中，由BeanFactory管理Bean的生成，销毁
24.         DefaultListableBeanFactory beanFactory = new DefaultListableBeanFactory();
25.         final BeanDefinition configDefinition = BeanDefinitionBuilder.genericBeanDefinition(MyConfig.class)
26. package com.leo.domain;
28. import lombok.Data;
30. @Data
31. public class Book {
32.     private Integer id;
34.     private String type;
36.     private String name;
38.     private String description;
39. }.setScope("singleton")
40. package com.leo.domain;
42. import lombok.Data;
44. @Data
45. public class Book {
46.     private Integer id;
48.     private String type;
50.     private String name;
52.     private String description;
53. }.getBeanDefinition();
54.         beanFactory.registerBeanDefinition("config", configDefinition);
56.         // 向BeanFactory上注册一些后处理器，这些后处理器可以解析@Configuration和@Bean这些注解
57.         AnnotationConfigUtils.registerAnnotationConfigProcessors(beanFactory);
59.         // BeanFactory后处理器，执行后处理操作，处理@Configuration注解，将bean1和bean2生成出来
60.         final Collection<BeanFactoryPostProcessor> beanFactoryPostProcessors = beanFactory.getBeansOfType(
61. package com.leo.domain;
63. import lombok.Data;
65. @Data
66. public class Book {
67.     private Integer id;
69.     private String type;
71.     private String name;
73.     private String description;
74. }BeanFactoryPostProcessor.class).values();
75.         log.info("---------------BeanFactory后处理器------------------");
76.         beanFactoryPostProcessors.forEach(beanFactoryPostProcessor -> log.info(beanFactoryPostProcessor.toString()));
77.         beanFactoryPostProcessors.forEach(beanFactoryPostProcessor -> {
78. package com.leo.domain;
80. import lombok.Data;
82. @Data
83. public class Book {
84.     private Integer id;
86.     private String type;
88.     private String name;
90.     private String description;
91. }beanFactoryPostProcessor.postProcessBeanFactory(beanFactory);
92.         });
93.         log.info("---------------BeanFactory后处理器------------------");
95.         // Bean后处理器，针对Bean的生命周期的各个阶段做扩展，例如@Autowired @Resource，
96.         // 这样才能在生成bean1后，向bean1中注入bean2
97.         final Collection<BeanPostProcessor> beanPostProcessors = beanFactory.getBeansOfType(BeanPostProcessor.class)
98. package com.leo.domain;
100. import lombok.Data;
102. @Data
103. public class Book {
104.     private Integer id;
106.     private String type;
108.     private String name;
110.     private String description;
111. }.values();
112.         log.info("----------------Bean后处理器-----------------");
113.         beanPostProcessors.forEach(beanPostProcessor -> log.info(beanPostProcessor.toString()));
114.         beanPostProcessors.forEach(beanFactory::addBeanPostProcessor);
115.         log.info("----------------Bean后处理器-----------------");
117.         log.info("------------------注册的所有Bean定义信息------------------");
118.         final String[] beanDefinitionNames = beanFactory.getBeanDefinitionNames();
119.         for (String beanDefinitionName : beanDefinitionNames) {
120. package com.leo.domain;
122. import lombok.Data;
124. @Data
125. public class Book {
126.     private Integer id;
128.     private String type;
130.     private String name;
132.     private String description;
133. }log.info(beanDefinitionName);
134.         }
135.         log.info("------------------注册的所有Bean定义信息------------------");
137.         final Bean1 bean1 = beanFactory.getBean(Bean1.class);
138.         log.info(bean1.getBean2().toString());
139.     }
141.     @Configuration
142.     static class MyConfig {
143.         @Bean
144.         public Bean1 bean1() {
145. package com.leo.domain;
147. import lombok.Data;
149. @Data
150. public class Book {
151.     private Integer id;
153.     private String type;
155.     private String name;
157.     private String description;
158. }return new Bean1();
159.         }
161.         @Bean
162.         public Bean2 bean2() {
163. package com.leo.domain;
165. import lombok.Data;
167. @Data
168. public class Book {
169.     private Integer id;
171.     private String type;
173.     private String name;
175.     private String description;
176. }return new Bean2();
177.         }
178.     }
180.     static class Bean1 {
182.         @Autowired
183.         private Bean2 bean2;
185.         public Bean1() {
186. package com.leo.domain;
188. import lombok.Data;
190. @Data
191. public class Book {
192.     private Integer id;
194.     private String type;
196.     private String name;
198.     private String description;
199. }log.info("Bean1 construct...");
200.         }
202.         public Bean2 getBean2() {
203. package com.leo.domain;
205. import lombok.Data;
207. @Data
208. public class Book {
209.     private Integer id;
211.     private String type;
213.     private String name;
215.     private String description;
216. }return bean2;
217.         }
218.     }
220.     static class Bean2 {
221.         public Bean2() {
222. package com.leo.domain;
224. import lombok.Data;
226. @Data
227. public class Book {
228.     private Integer id;
230.     private String type;
232.     private String name;
234.     private String description;
235. }log.info("Bean2 construct");
236.         }
237.     }
238. }

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以上代码的运行结果如下：

1. 10:56:43.379 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.annotation.internalConfigurationAnnotationProcessor'
2. 10:56:43.395 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.event.internalEventListenerProcessor'
3. 10:56:43.398 [main] INFO com.leo.ssmp.SsmpApplication - ---------------BeanFactory后处理器------------------
4. 10:56:43.398 [main] INFO com.leo.ssmp.SsmpApplication - org.springframework.context.annotation.ConfigurationClassPostProcessor@724af044
5. 10:56:43.398 [main] INFO com.leo.ssmp.SsmpApplication - org.springframework.context.event.EventListenerMethodProcessor@4678c730
6. 10:56:43.512 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.event.internalEventListenerFactory'
7. 10:56:43.513 [main] INFO com.leo.ssmp.SsmpApplication - ---------------BeanFactory后处理器------------------
8. 10:56:43.513 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.annotation.internalAutowiredAnnotationProcessor'
9. 10:56:43.513 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.annotation.internalCommonAnnotationProcessor'
10. 10:56:43.516 [main] INFO com.leo.ssmp.SsmpApplication - ----------------Bean后处理器-----------------
11. 10:56:43.516 [main] INFO com.leo.ssmp.SsmpApplication - org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor@6385cb26
12. 10:56:43.516 [main] INFO com.leo.ssmp.SsmpApplication - org.springframework.context.annotation.CommonAnnotationBeanPostProcessor@38364841
13. 10:56:43.517 [main] INFO com.leo.ssmp.SsmpApplication - ----------------Bean后处理器-----------------
14. 10:56:43.517 [main] INFO com.leo.ssmp.SsmpApplication - ------------------注册的所有Bean定义信息------------------
15. 10:56:43.517 [main] INFO com.leo.ssmp.SsmpApplication - config
16. 10:56:43.517 [main] INFO com.leo.ssmp.SsmpApplication - org.springframework.context.annotation.internalConfigurationAnnotationProcessor
17. 10:56:43.517 [main] INFO com.leo.ssmp.SsmpApplication - org.springframework.context.annotation.internalAutowiredAnnotationProcessor
18. 10:56:43.517 [main] INFO com.leo.ssmp.SsmpApplication - org.springframework.context.annotation.internalCommonAnnotationProcessor
19. 10:56:43.517 [main] INFO com.leo.ssmp.SsmpApplication - org.springframework.context.event.internalEventListenerProcessor
20. 10:56:43.517 [main] INFO com.leo.ssmp.SsmpApplication - org.springframework.context.event.internalEventListenerFactory
21. 10:56:43.517 [main] INFO com.leo.ssmp.SsmpApplication - bean1
22. 10:56:43.517 [main] INFO com.leo.ssmp.SsmpApplication - bean2
23. 10:56:43.517 [main] INFO com.leo.ssmp.SsmpApplication - ------------------注册的所有Bean定义信息------------------
24. 10:56:43.517 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'bean1'
25. 10:56:43.518 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'config'
26. 10:56:43.529 [main] INFO com.leo.ssmp.SsmpApplication - Bean1 construct...
27. 10:56:43.535 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'bean2'
28. 10:56:43.536 [main] INFO com.leo.ssmp.SsmpApplication - Bean2 construct
29. 10:56:43.537 [main] INFO com.leo.ssmp.SsmpApplication - com.leo.ssmp.SsmpApplication$Bean2@55040f2f
31. Process finished with exit code 0

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我们会发现这是容器里只有一个Bean，但是当我们用springboot自动配置来启动容器时，会发现即使我们不定义Bean，默认也会加载一些内置的bean。那么Spring是如何加载这些内置的Bean的呢。我们可以在xml文件中加入如下配置：

1. package com.leo.domain;
3. import lombok.Data;
5. @Data
6. public class Book {
7.     private Integer id;
9.     private String type;
11.     private String name;
13.     private String description;
14. }

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这样我们运行上面的代码时打印出来的结果如下：

1. 10:56:43.379 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.annotation.internalConfigurationAnnotationProcessor'
2. 10:56:43.395 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.event.internalEventListenerProcessor'
3. 10:56:43.398 [main] INFO com.leo.ssmp.SsmpApplication - ---------------BeanFactory后处理器------------------
4. 10:56:43.398 [main] INFO com.leo.ssmp.SsmpApplication - org.springframework.context.annotation.ConfigurationClassPostProcessor@724af044
5. 10:56:43.398 [main] INFO com.leo.ssmp.SsmpApplication - org.springframework.context.event.EventListenerMethodProcessor@4678c730
6. 10:56:43.512 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.event.internalEventListenerFactory'
7. 10:56:43.513 [main] INFO com.leo.ssmp.SsmpApplication - ---------------BeanFactory后处理器------------------
8. 10:56:43.513 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.annotation.internalAutowiredAnnotationProcessor'
9. 10:56:43.513 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.annotation.internalCommonAnnotationProcessor'
10. 10:56:43.516 [main] INFO com.leo.ssmp.SsmpApplication - ----------------Bean后处理器-----------------
11. 10:56:43.516 [main] INFO com.leo.ssmp.SsmpApplication - org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor@6385cb26
12. 10:56:43.516 [main] INFO com.leo.ssmp.SsmpApplication - org.springframework.context.annotation.CommonAnnotationBeanPostProcessor@38364841
13. 10:56:43.517 [main] INFO com.leo.ssmp.SsmpApplication - ----------------Bean后处理器-----------------
14. 10:56:43.517 [main] INFO com.leo.ssmp.SsmpApplication - ------------------注册的所有Bean定义信息------------------
15. 10:56:43.517 [main] INFO com.leo.ssmp.SsmpApplication - config
16. 10:56:43.517 [main] INFO com.leo.ssmp.SsmpApplication - org.springframework.context.annotation.internalConfigurationAnnotationProcessor
17. 10:56:43.517 [main] INFO com.leo.ssmp.SsmpApplication - org.springframework.context.annotation.internalAutowiredAnnotationProcessor
18. 10:56:43.517 [main] INFO com.leo.ssmp.SsmpApplication - org.springframework.context.annotation.internalCommonAnnotationProcessor
19. 10:56:43.517 [main] INFO com.leo.ssmp.SsmpApplication - org.springframework.context.event.internalEventListenerProcessor
20. 10:56:43.517 [main] INFO com.leo.ssmp.SsmpApplication - org.springframework.context.event.internalEventListenerFactory
21. 10:56:43.517 [main] INFO com.leo.ssmp.SsmpApplication - bean1
22. 10:56:43.517 [main] INFO com.leo.ssmp.SsmpApplication - bean2
23. 10:56:43.517 [main] INFO com.leo.ssmp.SsmpApplication - ------------------注册的所有Bean定义信息------------------
24. 10:56:43.517 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'bean1'
25. 10:56:43.518 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'config'
26. 10:56:43.529 [main] INFO com.leo.ssmp.SsmpApplication - Bean1 construct...
27. 10:56:43.535 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'bean2'
28. 10:56:43.536 [main] INFO com.leo.ssmp.SsmpApplication - Bean2 construct
29. 10:56:43.537 [main] INFO com.leo.ssmp.SsmpApplication - com.leo.ssmp.SsmpApplication$Bean2@55040f2f
31. Process finished with exit code 0org.springframework.context.annotation.internalConfigurationAnnotationProcessororg.springframework.context.annotation.internalAutowiredAnnotationProcessororg.springframework.context.annotation.internalCommonAnnotationProcessororg.springframework.context.event.internalEventListenerProcessororg.springframework.context.event.internalEventListenerFactory

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可以看到这时已经加载了很多处理注解和事件监听的Bean。
FileSystemXmlApplicationContext

基本原理与ClassPathXmlApplicationContext相似，只不过这里改为从文件系统直接读取xml配置。
AnnotationConfigApplicationContext

直接通过@Configuration注解的类来加载Bean，这种方法加载Bean时，会默认加载注解处理器这些内置的Bean。同时还会将config类也加载为Bean。

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