如何用Spring WebFlux返回404

Question

@RestController
@RequestMapping("/")
class CustomerController (private val service: CustomerService) {
    @GetMapping("/{id}")
    fun findById(@PathVariable id: String,
                 @RequestHeader(value = IF_NONE_MATCH) versionHeader: String?): Mono<HttpEntity<KundeResource>> =
        return service.findById(id)
            .switchIfEmpty(Mono.error(NotFoundException()))
            .map {
                // ETag stuff ...
                ok().eTag("...").body(...)
            }
}

Answer 1

当Spring5稳定时，我希望使用routefunction而不是@restcontroller。定义一个HandlerFunction来处理请求，然后声明一个routefunction来将请求映射到HandlerFunction：

public Mono<ServerResponse> get(ServerRequest req) {
    return this.posts
        .findById(req.pathVariable("id"))
        .flatMap((post) -> ServerResponse.ok().body(Mono.just(post), Post.class))
        .switchIfEmpty(ServerResponse.notFound().build());
}

在这里查看完整的示例代码。

Kotlin版本，定义一个函数来处理请求，使用routefunctionDSL将传入的请求映射到handlerfuncation：

fun get(req: ServerRequest): Mono<ServerResponse> {
    return this.posts.findById(req.pathVariable("id"))
            .flatMap { post -> ok().body(Mono.just(post), Post::class.java) }
            .switchIfEmpty(notFound().build())
}

fun get(req: ServerRequest): Mono<ServerResponse> = this.posts.findById(req.pathVariable("id"))
            .flatMap { post -> ok().body(Mono.just(post), Post::class.java) }
            .switchIfEmpty(notFound().build())

首先定义一个异常，例如。PostNotFoundException。然后把它扔进控制器。

 @GetMapping(value = "/{id}")
    public Mono<Post> get(@PathVariable(value = "id") Long id) {
        return this.posts.findById(id).switchIfEmpty(Mono.error(new PostNotFoundException(id)));
    }

定义ExceptionHandler来处理异常，并将其注册到HttpHandler中。

@Profile("default")
@Bean
public NettyContext nettyContext(ApplicationContext context) {
    HttpHandler handler = WebHttpHandlerBuilder.applicationContext(context)
        .exceptionHandler(exceptionHandler())
        .build();
    ReactorHttpHandlerAdapter adapter = new ReactorHttpHandlerAdapter(handler);
    HttpServer httpServer = HttpServer.create("localhost", this.port);
    return httpServer.newHandler(adapter).block();
}

@Bean
public WebExceptionHandler exceptionHandler() {
    return (ServerWebExchange exchange, Throwable ex) -> {
        if (ex instanceof PostNotFoundException) {
            exchange.getResponse().setStatusCode(HttpStatus.NOT_FOUND);
            return exchange.getResponse().setComplete();
        }
        return Mono.error(ex);
    };
}

在这里检查完整的代码。对于Spring Boot用户，请查看此示例。