在单体应用中实现定时触发外部API调用的策略

@RestController
@RequestMapping("/api")
public class ScheduledTaskController {

    private final ExternalApiService externalApiService;

    public ScheduledTaskController(ExternalApiService externalApiService) {
        this.externalApiService = externalApiService;
    }

    @PostMapping("/scheduled-trigger")
    public ResponseEntity<String> handleScheduledTrigger() {
        // 执行定时任务逻辑
        System.out.println("Scheduled trigger received from cloud event service.");
        // 调用核心业务方法
        processDelayedNotifications();
        return ResponseEntity.ok("Trigger processed successfully.");
    }

    private void processDelayedNotifications() {
        // 查找所有符合条件（例如：订单创建3天后）的记录
        // 遍历这些记录，并为每条记录调用外部API
        // externalApiService.sendNotification(orderId);
        System.out.println("Processing delayed notifications...");
        // 实际逻辑会查询数据库，筛选数据，然后调用外部API
    }
}

@SpringBootApplication
@EnableScheduling // 启用Spring的定时任务功能
public class MonolithicApplication {
    public static void main(String[] args) {
        SpringApplication.run(MonolithicApplication.class, args);
    }
}

import org.springframework.scheduling.annotation.Async;
import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Component;

import java.time.LocalDate;

@Component
public class NotificationScheduler {

    private final ExternalApiService externalApiService; // 假设有一个服务用于调用外部API

    public NotificationScheduler(ExternalApiService externalApiService) {
        this.externalApiService = externalApiService;
    }

    /**
     * 每天上午9点15分执行一次。
     * cron表达式格式: 秒 分 时 日 月 周
     * "0 15 9 ? * *" 表示：
     * 秒: 0 (整点)
     * 分: 15 (15分)
     * 时: 9 (上午9点)
     * 日: ? (不指定具体某天，与周冲突时使用)
     * 月: * (每月)
     * 周: * (每周)
     *
     * zone属性用于指定时区，确保任务在正确的时间执行。
     */
    @Scheduled(cron = "0 15 9 ? * *", zone = "Asia/Shanghai") // 例如，每天上午9点15分在上海时区执行
    @Async // 建议添加此注解，使定时任务在单独的线程中异步执行，避免阻塞主线程
    public void processDelayedNotifications() {
        System.out.println("Starting delayed notification processing at: " + LocalDate.now());

        // 核心业务逻辑：
        // 1. 查询数据库，找出所有订单中“下单日期 + 3天”等于当前日期的订单。
        //    例如：SELECT * FROM orders WHERE order_date = CURRENT_DATE - INTERVAL '3 DAY'
        // 2. 遍历这些订单，并对每个订单执行相应的操作。
        // 3. 调用外部API发送通知。
        //    externalApiService.sendNotificationForOrder(order.getOrderId());

        // 模拟调用外部API
        try {
            // externalApiService.callExternalApi();
            System.out.println("Successfully processed and potentially called external API for delayed notifications.");
        } catch (Exception e) {
            System.err.println("Error during delayed notification processing: " + e.getMessage());
            // 错误处理逻辑，例如记录日志、发送告警
        }
    }
}

@SpringBootApplication
@EnableScheduling
@EnableAsync // 启用Spring的异步方法执行
public class MonolithicApplication {
    public static void main(String[] args) {
        SpringApplication.run(MonolithicApplication.class, args);
    }
}

import org.springframework.stereotype.Service;
import org.springframework.web.reactive.function.client.WebClient;
import reactor.core.publisher.Mono;

@Service
public class ExternalApiService {

    private final WebClient webClient;

    public ExternalApiService(WebClient.Builder webClientBuilder) {
        this.webClient = webClientBuilder.baseUrl("http://external-api.com").build();
    }

    public Mono<String> sendNotification(String orderId, String message) {
        // 构建请求体
        NotificationRequest request = new NotificationRequest(orderId, message);

        return webClient.post()
                .uri("/notifications")
                .bodyValue(request)
                .retrieve()
                .bodyToMono(String.class) // 假设返回String
                .doOnSuccess(response -> System.out.println("Notification sent for order " + orderId + ": " + response))
                .doOnError(error -> System.err.println("Failed to send notification for order " + orderId + ": " + error.getMessage()));
    }

    // 内部类或DTO用于请求体
    private static class NotificationRequest {
        public String orderId;
        public String message;

        public NotificationRequest(String orderId, String message) {
            this.orderId = orderId;
            this.message = message;
        }
    }
}