Spring 容器接口

ApplicationContext和BeanFactory关系

继承

ApplicationContext是BeanFactory的子接口

组合

在ApplicationContext具体的实现类里，通常都组合了BeanFactory的功能

如上所示

BeanFactory 作用

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

DefaultListableBeanFactory 的类图

DefaultSingletonBeanRegistry 的成员变量singletonObjects存放所有单例对象kv关系

案例

利用反射机制获取beanFactory的singletonObjects 字段值


@Component
public class Component1 {

    private static final Logger log = LoggerFactory.getLogger(Component1.class);

    @Autowired
    private ApplicationEventPublisher context;

    public void register() {
        log.debug("用户注册");
        context.publishEvent(new UserRegisteredEvent(this));
    }

}


@Component
public class Component2 {

    private static final Logger log = LoggerFactory.getLogger(Component2.class);

    @EventListener
    public void aaa(UserRegisteredEvent event) {
        log.debug("{}", event);
        log.debug("发送短信");
    }
}


ConfigurableApplicationContext context = SpringApplication.run(A01.class, args);
Field singletonObjects = DefaultSingletonBeanRegistry.class.getDeclaredField("singletonObjects");
singletonObjects.setAccessible(true);
ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
Map<String, Object> map = (Map<String, Object>) singletonObjects.get(beanFactory);
map.entrySet().stream().filter(e -> e.getKey().startsWith("component"))
      .forEach(e -> {
             System.out.println(e.getKey() + "=" + e.getValue());
       });

ApplicationContext的扩展

类图中额外继承的接口就是ApplicationContext的扩展功能

国际化 MessageSource

ApplicationContext 接口扩展了一个名为 MessageSource 的接口，因此提供了国际化（“i18n”）功能。

MessageSource 接口定义和主要方法如下


public interface MessageSource {
    // 获取消息： code消息key args替换内支持{} default默认值 loc语言
	String getMessage(String code, Object[] args, String default, Locale loc);
    String getMessage(String code, Object[] args, Locale loc)
	String getMessage(String code, Object[] args, Locale loc)
}

在resources目录下新建messages.properties文件

messages_en.properties	`hi=Hello`
messages_ja.properties	`hi=こんにちは`
messages_zh.properties	`hi=你好`

调用getMessage方法


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));

ApplicationContext 中 MessageSource bean 的名字固定为 messageSource

使用 SpringBoot 时，国际化文件名固定为 messages

空的 messages.properties 也必须存在

ResourceLoader 访问资源

• 通过 ResourceLoader 接口访问资源，例如 URL 和文件


Resource[] resources = context.getResources("classpath*:META-INF/spring.factories");
        for (Resource resource : resources) {
            System.out.println(resource);
        }


URL [file:/E:/study/spring/spring-framwork/show/target/classes/META-INF/spring.factories]
URL [jar:file:/E:/evn/maven/maven_repository/org/springframework/boot/spring-boot/2.5.5/spring-boot-2.5.5.jar!/META-INF/spring.factories]
URL [jar:file:/E:/evn/maven/maven_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:/evn/maven/maven_repository/org/springframework/spring-beans/5.3.10/spring-beans-5.3.10.jar!/META-INF/spring.factories]
URL [jar:file:/E:/evn/maven/maven_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:/evn/maven/maven_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:/evn/maven/maven_repository/org/springframework/spring-test/5.3.10/spring-test-5.3.10.jar!/META-INF/spring.factories]

EnvironmentCapable获取环境变量


System.out.println(context.getEnvironment().getProperty("java_home"));
        System.out.println(context.getEnvironment().getProperty("server.port"));

ApplicationListener事件机制

继承ApplicationEvent 自定义事件


public class UserRegisteredEvent extends ApplicationEvent {
    public UserRegisteredEvent(Object source) {
        super(source);
    }
}

context.publishEvent() 发布事件


@Component
public class Component1 {

    private static final Logger log = LoggerFactory.getLogger(Component1.class);

    @Autowired
    private ApplicationEventPublisher context;

    public void register() {
        log.debug("用户注册");
        context.publishEvent(new UserRegisteredEvent(this));
    }

}

@EventListener监听事件


@Component
public class Component2 {

    private static final Logger log = LoggerFactory.getLogger(Component2.class);

    @EventListener
    public void aaa(UserRegisteredEvent event) {
        log.debug("{}", event);
        log.debug("发送短信");
    }
}

测试 context.getBean(Component1.class).register();


[DEBUG] 17:09:30.963 [main] com.onethink.a01.Component1         - 用户注册 
[DEBUG] 17:09:30.964 [main] com.onethink.a01.Component2         - com.onethink.a01.UserRegisteredEvent[source=com.onethink.a01.Component1@415795f3] 
[DEBUG] 17:09:30.964 [main] com.onethink.a01.Component2         - 发送短信