Spring Boot ApplicationRunner

什么是 `ApplicationRunner` 和 `CommandLineRunner`？

Spring Boot 提供了两个接口，用于在 应用上下文（ApplicationContext）完全初始化后 执行自定义逻辑：

1. `CommandLineRunner`

@FunctionalInterface
public interface CommandLineRunner {void run(String... args) throws Exception;
}

接收的是 main 方法传入的原始命令行参数
更贴近“命令行应用”语义

2. `ApplicationRunner`

@FunctionalInterface
public interface ApplicationRunner {void run(ApplicationArguments args) throws Exception;
}

参数是封装后的 ApplicationArguments，可方便地解析 --option 和非选项参数
功能更强大，推荐使用

实战：五大核心应用场景

场景一：缓存预热（Cache Warm-up）

@Component
@Order(1) // 优先执行
@Slf4j
public class CacheWarmupRunner implements ApplicationRunner {@Autowiredprivate ProductService productService;@Autowiredprivate RedisTemplate<String, Object> redisTemplate;@Overridepublic void run(ApplicationArguments args) {log.info("Starting cache warm-up...");List<Product> products = productService.getAllActiveProducts();products.forEach(product -> redisTemplate.opsForValue().set("product:" + product.getId(), product, Duration.ofHours(24)));log.info("Cache warm-up completed. Loaded {} products.", products.size());}
}

✅ 避免“缓存雪崩”，提升首访性能

场景二：启动后健康检查（Post-Startup Health Check）

@Component
@Order(2)
@Slf4j
public class PostStartupHealthCheckRunner implements ApplicationRunner {@Autowiredprivate RestTemplate restTemplate;@Autowiredprivate DataSource dataSource;@Overridepublic void run(ApplicationArguments args) {log.info("Running post-startup health checks...");try {// 检查外部服务String result = restTemplate.getForObject("http://payment-service/health", String.class);log.info("Payment service health: {}", result);// 检查数据库try (Connection conn = dataSource.getConnection()) {Assertions.assertTrue(conn.isValid(2));}log.info("Database connection OK.");} catch (Exception e) {log.error("Health check failed!", e);// 可选择：发送告警、标记服务为“不健康”等// 注意：这里抛异常会阻止应用启动！需根据策略处理}}
}

⚠️ 注意：若任务失败，可能阻止应用启动。生产环境建议异步或降级处理。

场景三：异步加载非关键数据

@Component
@Slf4j
public class AsyncDataLoaderRunner implements ApplicationRunner {@Autowiredprivate AsyncTaskExecutor taskExecutor; // 如 SimpleAsyncTaskExecutor@Autowiredprivate ReportService reportService;@Overridepublic void run(ApplicationArguments args) {log.info("Scheduling async data loading...");taskExecutor.execute(() -> {try {reportService.preloadMonthlyReports();log.info("Monthly reports preloaded.");} catch (Exception e) {log.warn("Async preload failed, will retry later.", e);}});}
}