Spring Boot 4 Complete Guide · 课时

使用 @Scheduled 调度任务

利用 Spring 内置的任务调度支持，按照固定间隔或 cron 计划运行后台任务。

使用 @Scheduled 调度任务 是 CoddyKit 上的免费 Spring Boot 4 Complete Guide 课时。这是第 4 节课，共 4 节。你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。这是 Spring Boot 4 Complete Guide 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Spring Boot 4 Complete Guide 课程共包含 4 节课。

本课时的部分内容尚未翻译，以英文显示。

Why Scheduled Tasks?

Many applications need work to run periodically: cleaning up data, sending digests, refreshing caches. Spring provides scheduling without an external job framework.

Enabling Scheduling

Add @EnableScheduling to a configuration class to activate Spring's scheduler.

@EnableScheduling
@Configuration
public class SchedulingConfig {
}

Fixed Rate Execution

The fixedRate option runs a method every N milliseconds, measured from the start of each run.

@Scheduled(fixedRate = 5000)
public void poll() {
    System.out.println("Polling");
}

Fixed Delay Execution

fixedDelay waits N milliseconds after the previous run finishes, preventing overlap when a task takes a while.

@Scheduled(fixedDelay = 5000)
public void process() {
}

Rate vs Delay

Use fixedRate for steady cadence and fixedDelay when each run must fully complete before the next begins. Choosing wrong can cause overlapping executions.

Cron Expressions

For calendar-based timing use cron. The expression has six fields: second, minute, hour, day, month, weekday.

@Scheduled(cron = "0 0 2 * * *")
public void nightlyJob() {
}

Reading the Cron Above

0 0 2 * * * means at second 0, minute 0, hour 2, every day, every month, any weekday, that is, 2 AM daily.

Initial Delay

The initialDelay attribute postpones the first execution, useful for letting the app warm up before background work begins.

@Scheduled(fixedRate = 5000, initialDelay = 10000)
public void start() {
}

Avoiding Blocking the Scheduler

By default a single thread runs all scheduled tasks. A long task can delay others, so configure a thread pool or pair scheduling with @Async for heavy work.

Scheduling in Clusters

If you run multiple instances, each will fire the same schedule. Use a distributed lock (for example ShedLock) to ensure a job runs once across the cluster.

Externalizing the Schedule

Put the cron expression in properties so you can change timing per environment without recompiling.

@Scheduled(cron = "${cleanup.cron}")
public void cleanup() {
}

Quick Check

Test your understanding of scheduled tasks.

Recap

You enabled scheduling and used fixedRate, fixedDelay, cron expressions, and initial delays. You also learned to externalize schedules and to coordinate jobs safely across a cluster.

常见问题解答

「使用 @Scheduled 调度任务」课时是免费的吗？

是的 — 「使用 @Scheduled 调度任务」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 Spring Boot 4 Complete Guide 课程的其余内容，请升级到 CoddyKit PRO。 Spring Boot 4 Complete Guide 课程共包含 4 节课。

「使用 @Scheduled 调度任务」这节课中我会学到什么？

利用 Spring 内置的任务调度支持，按照固定间隔或 cron 计划运行后台任务。你通过在浏览器中直接运行的动手代码来练习 Spring Boot 4 Complete Guide，全天候 AI 导师会在你学习这节课的过程中回答你的问题。

学习 Spring Boot 4 Complete Guide 需要有经验吗？

无需任何先前经验。CoddyKit 上的 Spring Boot 4 Complete Guide 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。这是第 4 节课，共 4 节。

「使用 @Scheduled 调度任务」课时需要多长时间？

大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。

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能。每节 Spring Boot 4 Complete Guide 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。

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