Spring Boot 4 Microservices & REST APIs · 课时

响应式控制器

使用 WebFlux 构建非阻塞端点

响应式控制器 是 CoddyKit 上的免费 Spring Boot 4 Microservices & REST APIs 课时。这是第 2 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 Microservices & REST APIs 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 Microservices & REST APIs 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。

Reactive Web Endpoints

With WebFlux you write @RestController classes just like in Spring MVC, but methods return reactive types instead of plain objects.

Return Mono<T> for a single resource
Return Flux<T> for a collection or stream

Returning a Mono

A handler returning Mono resolves to a single JSON object. The framework subscribes for you.

@RestController
@RequestMapping("/users")
public class UserController {
    @GetMapping("/{id}")
    public Mono<User> getUser(@PathVariable String id) {
        return userService.findById(id);
    }
}

Returning a Flux

A handler returning Flux serializes to a JSON array by default.

@GetMapping
public Flux<User> getAllUsers() {
    return userService.findAll();
}

No Blocking Allowed

Inside reactive handlers you must not call blocking code. Return the publisher and let the chain stay reactive.

// BAD: blocks the event loop
@GetMapping("/bad")
public User bad() {
    return userService.findById("1").block();
}

// GOOD: stays reactive
@GetMapping("/good")
public Mono<User> good() {
    return userService.findById("1");
}

Path and Query Params

Binding annotations work the same as in MVC: @PathVariable, @RequestParam, and @RequestBody.

@GetMapping("/search")
public Flux<User> search(@RequestParam String name) {
    return userService.findByName(name);
}

Accepting a Reactive Body

A POST handler can accept a Mono request body, keeping the whole flow non-blocking.

@PostMapping
public Mono<User> create(@RequestBody Mono<User> body) {
    return body.flatMap(userService::save);
}

Setting Status Codes

Use @ResponseStatus or wrap results in ResponseEntity within a Mono.

@PostMapping
@ResponseStatus(HttpStatus.CREATED)
public Mono<User> create(@RequestBody Mono<User> body) {
    return body.flatMap(userService::save);
}

ResponseEntity in a Mono

To control headers and status dynamically, return Mono<ResponseEntity<T>>.

@GetMapping("/{id}")
public Mono<ResponseEntity<User>> getUser(@PathVariable String id) {
    return userService.findById(id)
        .map(ResponseEntity::ok)
        .defaultIfEmpty(ResponseEntity.notFound().build());
}

Streaming with Server-Sent Events

Set the content type to text/event-stream to stream a Flux to the client over time.

@GetMapping(value = "/stream",
    produces = MediaType.TEXT_EVENT_STREAM_VALUE)
public Flux<Long> stream() {
    return Flux.interval(Duration.ofSeconds(1));
}

Error Handling

Use onErrorResume to map errors to a fallback publisher, or a @ControllerAdvice for global handling.

@GetMapping("/{id}")
public Mono<User> getUser(@PathVariable String id) {
    return userService.findById(id)
        .onErrorResume(e -> Mono.error(
            new ResponseStatusException(HttpStatus.NOT_FOUND)));
}

The Netty Server

WebFlux runs on Netty by default — an event-loop server with a small fixed thread pool. This is why blocking calls are so harmful: blocking one thread stalls many requests.

Quick Check

Test your understanding of reactive controllers.

Recap

You learned how to build reactive endpoints:

@RestController methods return Mono or Flux
Never call block() inside a handler
Use ResponseEntity in a Mono for dynamic status
Stream with text/event-stream

常见问题解答

「响应式控制器」课时是免费的吗？

是的 — 「响应式控制器」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 Microservices & REST APIs 课程的其余内容，请升级到 CoddyKit PRO。 Spring Boot 4 Microservices & REST APIs 课程共包含 4 节课。

「响应式控制器」这节课中我会学到什么？

使用 WebFlux 构建非阻塞端点你通过在浏览器中直接运行的动手代码来练习 Spring Boot 4 Microservices & REST APIs，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 Microservices & REST APIs 需要有经验吗？

无需任何先前经验。CoddyKit 上的 Spring Boot 4 Microservices & REST APIs 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 2 节课，共 4 节。

「响应式控制器」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。

我能在这节 Spring Boot 4 Microservices & REST APIs 课中编写并运行代码吗？

能。每节 Spring Boot 4 Microservices & REST APIs 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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