容器接口BeanFactory和ApplicationContext

1. BeanFactory能做哪些事
2. ApplicationContext有哪些扩展功能
3. 事件解耦

重点

到底什么是BeanFactory

1. 它是 ApplicationContext 的父接口
2. 它才是 Spring 的核心容器, 主要的 ApplicationContext 实现都【组合】了它的功能

BeanFactory 能干点啥

1. 表面上只有 getBean
2. 实际上控制反转、基本的依赖注入、直至 Bean 的生命周期的各种功能, 都由它的实现类提供

ApplicationContext扩展了哪些功能

扩展了以下接口：MessageSource、ResourcePatternResolver、EnvironmentCapable、ApplicationEventPublisher

1. MessageSource的getMessage方法：用来翻译多国语言，提供翻译能力

2. ResourcePatternResolver的getResources：提供使用通配符来匹配资源的能力

3. EnvironmentCapable的getEnvironment方法：提供获取环境变量的能力

4. ApplicationEventPublisher的pulishEven方法：发布事件的能力

代码

/*
    BeanFactory 与 ApplicationContext 的区别
 */
@SpringBootApplication(exclude = {DataSourceAutoConfiguration.class, DruidDataSourceAutoConfigure.class})
public class A01 {

    private static final Logger log = LoggerFactory.getLogger(A01.class);

    public static void main(String[] args) throws NoSuchFieldException, IllegalAccessException, IOException {
        ConfigurableApplicationContext context = SpringApplication.run(A01.class, args);
        // 在这里打断点可以看到context里有BeanFactory对象
//        context.getBean("aaa");
        System.out.println(context);


        /*
            2. BeanFactory 能干点啥
                - 表面上只有 getBean
                - 实际上控制反转、基本的依赖注入、直至 Bean 的生命周期的各种功能, 都由它的实现类提供
         */
        // BeanFactory实际上是DefaultListableBeanFactory类型，DefaultListableBeanFactory又继承了DefaultSingletonBeanRegistry
        Field singletonObjects = DefaultSingletonBeanRegistry.class.getDeclaredField("singletonObjects");
        singletonObjects.setAccessible(true);
        ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
        // get方法，传入该Field的类类型对象，返回该队形中的该字段值
        Map<String, Object> o = (Map<String, Object>) singletonObjects.get(beanFactory);
        o.forEach((key, value) -> {
            if (!key.startsWith("component")) {
                return;
            }
            System.out.println(key + "-----" + value);
        });

        /*
            3. ApplicationContext 比 BeanFactory 多点啥
         */
        // MessageSource：用来翻译多国语言，提供翻译能力
        System.out.println(context.getMessage("hi", null, Locale.CHINA));
        System.out.println(context.getMessage("hi", null, Locale.ENGLISH));
        System.out.println(context.getMessage("hi", null, Locale.JAPANESE));


        // ResourcePatternResolver：提供使用通配符来匹配资源的能力
        // classpath和classpath*的区别
//        Resource[] resources = context.getResources("classpath:META-INF/spring.factories");
        Resource[] resources = context.getResources("classpath*:META-INF/spring.factories");
        for (Resource resource : resources) {
            System.out.println(resource);
        }

        // EnvironmentCapable：提供获取环境变量的能力
        System.out.println(context.getEnvironment().getProperty("java_home"));
        System.out.println(context.getEnvironment().getProperty("server.port"));

        // ApplicationEventPublisher：发布事件的能力
        context.publishEvent(new UserRegisteredEvent(context));
//        context.getBean(Component1.class).register();
    }

component1-----com.shunyum.a01.Component1@4a0df195
component2-----com.shunyum.a01.Component2@42fcc7e6
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Hello
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URL [jar:file:/E:/Maven/repository/repository/org/springframework/boot/spring-boot/2.5.5/spring-boot-2.5.5.jar!/META-INF/spring.factories]
URL [jar:file:/E:/Maven/repository/repository/org/springframework/boot/spring-boot-autoconfigure/2.5.5/spring-boot-autoconfigure-2.5.5.jar!/META-INF/spring.factories]
URL [jar:file:/E:/Maven/repository/repository/org/springframework/spring-beans/5.3.23/spring-beans-5.3.23.jar!/META-INF/spring.factories]
URL [jar:file:/E:/Maven/repository/repository/org/mybatis/spring/boot/mybatis-spring-boot-autoconfigure/2.2.0/mybatis-spring-boot-autoconfigure-2.2.0.jar!/META-INF/spring.factories]
URL [jar:file:/E:/Maven/repository/repository/com/alibaba/druid-spring-boot-starter/1.2.8/druid-spring-boot-starter-1.2.8.jar!/META-INF/spring.factories]
URL [jar:file:/E:/Maven/repository/repository/org/springframework/spring-test/5.3.23/spring-test-5.3.23.jar!/META-INF/spring.factories]
E:\JAVA\Java
8080
2023-04-06 23:44:01.778 DEBUG 15040 --- [           main] com.shunyum.a01.Component2               : com.shunyum.a01.UserRegisteredEvent[source=org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext@649bec2e, started on Thu Apr 06 23:44:00 CST 2023]
2023-04-06 23:44:01.779 DEBUG 15040 --- [           main] com.shunyum.a01.Component2               : 发送短信