SpringBoot常用的扩展点及使用场景

ApplicationContextAware

@Component
public class ApplicationContextHolder implements ApplicationContextAware {
    private static ApplicationContext context;

    @Override
    public void setApplicationContext(@NonNull ApplicationContext applicationContext) throws BeansException {
        //可以在不被spring管理的类中，获取bean和系统属性
        context = applicationContext;
    }

    public static ApplicationContext getApplicationContext() {
        return context;
    }

    public static <T> T getBean(Class<T> tClass) {
        return context.getBean(tClass);
    }

    public static Environment getEnvironment() {
        return context.getEnvironment();
    }

    public static String getProperty(String name) {
        return context.getEnvironment().getProperty(name);
    }
}

InitializingBean

@Component
public class InitializingBeanTest implements InitializingBean {

    @Override
    public void afterPropertiesSet() throws Exception {
        //在当前bean初始化完成后进行操作，对bean进行初始化操作，如构造责任链
        System.out.println("InitializingBeanTest.afterPropertiesSet");
    }
}

SmartInitializingSingleton

@Component
public class SmartInitializingSingletonTest implements SmartInitializingSingleton {
    @Override
    public void afterSingletonsInstantiated() {
        //所有单例bean初始化之后执行，可以进行缓存预热，开启流量入口
        System.out.println("afterSingletonsInstantiated");
    }
}

CommandLineRunner

@Component
public class CommandLineRunnerTest implements CommandLineRunner {
    @Override
    public void run(String... args) throws Exception {
        //spring初始化完成之后执行，可以初始化数据，执行一些脚本命令
        System.out.println("CommandLineRunner");
    }
}

ApplicationListener

@Component
public class ApplicationListenerTest implements ApplicationListener<ContextRefreshedEvent> {
    @Override
    public void onApplicationEvent(ContextRefreshedEvent event) {
        //可以监听各种事件，如刷新事件
        System.out.println("ApplicationListener.ContextRefreshedEvent");
    }
}