响应式 Spring WebClient 调用

Question

我正在尝试了解 WebFlux，但在 Webclient 调用方面遇到了一些麻烦。 我没有看到这一行 System.out.println("customerId = " + customerId); 执行它似乎没有调用端点。 但是如果我用 .subscribe(customer -> {}); 订阅 webclient; 然后我可以看到这一行 System.out.println("customerId = " + customerId); 在端点端工作。 我不明白为什么我必须订阅 Mono 调用，还是必须订阅？ 谢谢

@GetMapping("/customer/{customerId}")
@ResponseStatus(HttpStatus.ACCEPTED)
public Mono<Void> getCustomer(@PathVariable("customerId") int customerId) {
     WebClient webClient = WebClient.builder().baseUrl("http://localhost:8080").build();

 webClient.get()
  .uri("/client/customer/{customerId}",customerId)
  .accept(MediaType.APPLICATION_JSON)
  .retrieve()
  .bodyToMono(Customer.class);//here do I have to subscribe to actually activate to call?

 return null;
}


@GET
@Path("/customer/{customerId}")
@Produces(MediaType.APPLICATION_JSON)
public Customer getCustomer(@PathParam("customerId") int customerId) throws InterruptedException {
    System.out.println("customerId = " + customerId);  // I do not see the call comes thru if I dont subscribe to flux call.
    return new Customer(customerId,"custName");
} 

Answer 1

如果要从WebClient返回反应类型，则必须从控制器方法返回它，例如：

@GetMapping("/customer/{customerId}")
@ResponseStatus(HttpStatus.ACCEPTED)
public Mono<Customer> getCustomer(@PathVariable("customerId") int customerId) {
     WebClient webClient = WebClient.builder().baseUrl("http://localhost:8080").build();

 return webClient.get()
  .uri("/client/customer/{customerId}",customerId)
  .accept(MediaType.APPLICATION_JSON)
  .retrieve()
  .bodyToMono(Customer.class);
}

您还可以从您的端点返回一个Customer并阻止并等待您的WebClient的结果并离开响应式生态系统，例如：

@GetMapping("/customer/{customerId}")
@ResponseStatus(HttpStatus.ACCEPTED)
public Customer getCustomer(@PathVariable("customerId") int customerId) {
     WebClient webClient = WebClient.builder().baseUrl("http://localhost:8080").build();

 return webClient.get()
  .uri("/client/customer/{customerId}",customerId)
  .accept(MediaType.APPLICATION_JSON)
  .retrieve()
  .bodyToMono(Customer.class)
  .block()
}

如果您正在查看 Spring 的WebClient的一般介绍，请查看本教程