[Java知识库]Spring IOC容器和元信息来源

BeanFactory和ApplicationContext谁才是Spring Ioc容器？

BeanFactory 接口提供了能够管理任何类型对象的高级配置机制。ApplicationContext 是BeanFactory 的子接口。ApplicationContext添加了以下特性:

1. 更容易与 Spring 的 AOP 特性集成
2. 消息资源处理(用于国际化)
3. 事件发布。
4. 应用层特定的上下文，例如 web 应用程序中使用的 WebApplicationContext。

1. public?interface?ApplicationContext?extends?EnvironmentCapable,?ListableBeanFactory,?HierarchicalBeanFactory,
2. ??MessageSource,?ApplicationEventPublisher,?ResourcePatternResolver?{

1. public?interface?ListableBeanFactory?extends?BeanFactory?{

简而言之，BeanFactory 提供了配置框架和基本功能，而ApplicationContext 添加了更多特定于企业的功能。

总结：BeanFactory和ApplicationContext可以说都是Spring Ioc容器，在底层实现时，ApplicationContext不止实现了BeanFactory接口，同时还组合了BeanFactory的另一个实现类DefaultListableBeanFactory。

1. public?class?ClassPathXmlApplicationContext?extends?AbstractXmlApplicationContext?{
2. public?abstract?class?AbstractXmlApplicationContext?extends?AbstractRefreshableConfigApplicationContext?{
3. public?abstract?class?AbstractRefreshableConfigApplicationContext?extends?AbstractRefreshableApplicationContext
4. ??implements?BeanNameAware,?InitializingBean?{
5. public?abstract?class?AbstractRefreshableApplicationContext?extends?AbstractApplicationContext?{
7. ?@Nullable
8. ?private?Boolean?allowBeanDefinitionOverriding;
10. ?@Nullable
11. ?private?Boolean?allowCircularReferences;
13. ?/**?Bean?factory?for?this?context.?*/
14. ?@Nullable
15. ?private?DefaultListableBeanFactory?beanFactory;
17. @Override
18. ?public?final?ConfigurableListableBeanFactory?getBeanFactory()?{
19. ??synchronized?(this.beanFactoryMonitor)?{
20. ???if?(this.beanFactory?==?null)?{
21. ????throw?new?IllegalStateException("BeanFactory?not?initialized?or?already?closed?-?"?+
22. ??????"call?'refresh'?before?accessing?beans?via?the?ApplicationContext");
23. ???}
24. ???return?this.beanFactory;
25. ??}
26. ?}

configurableApplicationContext <-ApplicationContext<-BeanFactory
configurableApplicationContext#getBeanFactory()

Spring容器启动的过程中，会将Bean解析成Spring内部的BeanDefinition结构。 不管是是通过xml配置文件的 <Bean> 标签，还是通过注解配置的 @Bean ，还是 @Compontent 标注的类，还是扫描得到的类，它最终都会被解析成一个BeanDefinition对象，最后Bean工厂就会根据这份Bean的定义信息，对bean进行实例化、初始化等等操作。

Bean定义配置注意基于xml文件、properties文件、Java注解以及java Api;

Ioc容器配置注意基于xml文件、Java注解以及Java Api；

外部化属性配置基于Java注解 @Value。

Spring IoC依赖注入

1. public?class?UserRepository?{
2. ????/**
3. ?????*?自定义bean
4. ?????*/
5. ????private?Collection<User>?users;
7. ????/**
8. ?????*?bean工厂
9. ?????*?内建非bean对象
10. ?????*/
11. ????private?BeanFactory?beanFactory;
13. ????private?ObjectFactory<User>?userObjectFactory;
15. ????private?ObjectFactory<ApplicationContext>?objectFactory;
17. ????public?ObjectFactory<ApplicationContext>?getObjectFactory()?{
18. ????????return?objectFactory;
19. ????}
21. ????public?void?setObjectFactory(ObjectFactory<ApplicationContext>?objectFactory)?{
22. ????????this.objectFactory?=?objectFactory;
23. ????}
25. ????public?ObjectFactory<User>?getUserObjectFactory()?{
26. ????????return?userObjectFactory;
27. ????}
29. ????public?void?setUserObjectFactory(ObjectFactory<User>?userObjectFactory)?{
30. ????????this.userObjectFactory?=?userObjectFactory;
31. ????}
33. ????public?Collection<User>?getUsers()?{
34. ????????return?users;
35. ????}
37. ????public?BeanFactory?getBeanFactory()?{
38. ????????return?beanFactory;
39. ????}
41. ????public?void?setBeanFactory(BeanFactory?beanFactory)?{
42. ????????this.beanFactory?=?beanFactory;
43. ????}
45. ????public?void?setUsers(Collection<User>?users)?{
46. ????????this.users?=?users;
47. ????}
48. }

Xml配置信息

1. <?xml?version="1.0"?encoding="UTF-8"?>
2. <beans?xmlns="http://www.springframework.org/schema/beans"
3. ???????xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
4. ???????xsi:schemaLocation="http://www.springframework.org/schema/beans
5. ????????https://www.springframework.org/schema/beans/spring-beans.xsd">
7. ????<bean?id="user"?class="org.mango.spring.ioc.overview.domain.User"?>
8. ????????<property?name="id"?value="1"/>
9. ????????<property?name="name"?value="mango"/>
10. ????</bean>
12. ????<bean?id="superUser"?class="org.mango.spring.ioc.overview.domain.SuperUser"?parent="user"?primary="true">
13. ????????<property?name="address"?value="西安"></property>
14. ????</bean>
16. ????<bean?id="objectFactory"?class="org.springframework.beans.factory.config.ObjectFactoryCreatingFactoryBean"?>
17. ????????<property?name="targetBeanName"?value="user"></property>
18. ????</bean>
20. </beans>

1. <?xml?version="1.0"?encoding="UTF-8"?>
2. <beans?xmlns="http://www.springframework.org/schema/beans"
3. ???????xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
4. ???????xmlns:util="http://www.springframework.org/schema/util"
5. ???????xsi:schemaLocation="
6. ????????http://www.springframework.org/schema/beans?https://www.springframework.org/schema/beans/spring-beans.xsd
7. ????????http://www.springframework.org/schema/util?https://www.springframework.org/schema/util/spring-util.xsd">
10. ????<!--通过导入复用?dependency-->
11. ????<import?resource="dependency-lookup-context.xml"></import>
13. ????<!--autowire自动注入-->
14. ????<bean?id="userRepository"?class="org.mango.spring.ioc.overview.repository.UserRepository"
15. ??????????autowire="byType">?
16. ????????<!--硬编码-->
17. ?????<!--???<property?name="users">
18. ????????????<util:list>
19. ????????????????<ref?bean="user"/>
20. ????????????????<ref?bean="superUser"/>
21. ????????????</util:list>
22. ????????</property>-->
23. ????</bean>
25. </beans>

1. ?//配置xml文件?启动spring?应用上下文
2. ????????BeanFactory?beanFactory?=?new?ClassPathXmlApplicationContext("META-INF/dependency-injection-context.xml");
3. ????????//来源1：?自定义bean
4. ????????UserRepository?userRepository?=?(UserRepository)?beanFactory.getBean("userRepository");
6. ????????//实时注入bean
7. ????????userRepository.getUsers().forEach(System.out::println);
8. ????????//来源2:?依赖注入?（内建依赖）
9. ????????System.out.println(userRepository.getBeanFactory());
10. ????????System.out.println(userRepository.getBeanFactory()?==?beanFactory);
12. ????????//延时注入
13. ????????ObjectFactory?userFactory?=?userRepository.getUserObjectFactory();
14. ????????System.out.println(userFactory.getObject());
16. ????????ObjectFactory?objectFactory?=?userRepository.getObjectFactory();
17. ????????System.out.println(objectFactory.getObject());
19. ????????System.out.println(objectFactory.getObject()?==?beanFactory);
20. ????????//来源三：?容器内建?bean
21. ????????Environment?environment?=?beanFactory.getBean(Environment.class);

? ? ? ? ? ? ? ? ?System.out.println("获取Environment类型的bean"?+?environment);

?System.out.println(userRepository.getBeanFactory()?==?beanFactory); 输出为false