在应用程序启动前运行自定义代码的不同方法

Question

您能否描述在应用程序启动数据初始化或其他操作之前运行自定义代码的不同方法？（如ApplicationListener、CommandLineRunner等）

它们之间有什么不同？在哪种情况下使用它们更好？我想知道的不仅仅是一种方法，而是一种理解什么时候和什么我需要使用。

这里有一个足够老的问题，有太多的选项可以这样做：在Spring Boot开始后运行代码

如果问这个问题是一个错误的地方，请给我指出正确的地方。

Answer 1

我知道哪些选项：

>

CommandLineRunner-以字符串形式接收命令行参数

@Slf4j
@Component
public class DemoCommandLineRunner implements CommandLineRunner {

    @Override
    public void run(String... args) {
        log.info("[CommandLineRunner] Args: " + Arrays.toString(args));
    }
}

ApplicationRunner-接收带有名称的命令行参数

@Slf4j
@Component
public class DemoApplicationRunner implements ApplicationRunner {

    @Override
    public void run(ApplicationArguments args) {
        log.info("[ApplicationRunner] Args: ");
        nonOptionArgs(args);
        optionArgs(args);
    }

    private void nonOptionArgs(ApplicationArguments args) {
        args.getNonOptionArgs().forEach(log::info);
    }

    private void optionArgs(ApplicationArguments args) {
        args.getOptionNames().stream()
                .map(args::getOptionValues)
                .map(Objects::toString)
                .forEach(log::info);
    }
}

@Slf4j
@Component
public class DemoApplicationListener implements ApplicationListener<ApplicationEvent> {

    @Override
    public void onApplicationEvent(ApplicationEvent event) {
        logEvent(event);
    }

    private void logEvent(ApplicationEvent event) {
        log.info("[DemoApplicationListener] Event: " + event);
    }
}

@Slf4j
@Component
public class DemoEventApplicationListener {

    @EventListener
    public void handleContextRefreshedEvent(ContextRefreshedEvent event) {
        logEvent(event);
    }

    @EventListener
    public void handleApplicationReadyEvent(ApplicationReadyEvent event) {
        logEvent(event);
    }

    private void logEvent(ApplicationEvent event) {
        log.info("[DemoEventApplicationListener] Event: " + event);
    }
}

@Slf4j
@Component
public class DemoSmartLifecycle implements SmartLifecycle {

    private boolean isRunning;

    @Override
    public void start() {
        isRunning = true;
        log.info("[DemoSmartLifecycle]: Start");
    }

    @Override
    public void stop() {
        isRunning = false;
        log.info("[DemoSmartLifecycle]: Stop");
    }

    @Override
    public boolean isRunning() {
        return isRunning;
    }
}

@Slf4j
@Component
public class DemoSmartInitializingSingleton implements SmartInitializingSingleton {

    @Override
    public void afterSingletonsInstantiated() {
        log.info("[SmartInitializingSingleton] afterSingletonsInstantiated");
    }
}