Spring 5 WebClient 仅在 .exchange() 之后使用 .block() 时进行 Http 调用

Question

此调用按预期工作并使 POST 成功：

public class MyService implements IMyService {

private final WebClient webClient;
private final String url;

MyService(@Qualifier("web-client") WebClient webClient,
                      String url) {
    this.webClient = webClient;
    this.url = url;
}

@SneakyThrows
@Override
public void execute(Long jobId) {
    MultiValueMap<String, String> requestParms = new LinkedMultiValueMap<>();
    requestParms.add("arguments", "--batchJobId=" + jobId.toString());
    HttpEntity<MultiValueMap<String, String>> requestEntity =
        new HttpEntity<>(requestParms, null);

    final WebClient.ResponseSpec responseSpec = webClient.post()
        .uri(new URI(url + "/tasks/executions"))
        .body(BodyInserters.fromMultipartData(requestParms))
        .exchange()
        .block();
}
}

内部配置class:

@Bean
@Qualifier("web-client")
public WebClient getWebClient() {
    return WebClient.builder()
        .filter(basicAuthentication("user", "pass"))
        .filter(printLnFilter())
        .build();
}

private ExchangeFilterFunction printLnFilter() {
    return (request, next) -> {
        System.out.println("\n\n" + request.method().toString().toUpperCase() + ":\n\nURL:"
            + request.url().toString() + ":\n\nHeaders:" + request.headers().toString() + "\n\nAttributes:"
            + request.attributes() + "\n\n");

        return next.exchange(request);
    };
}

在上面的示例中，我们看到记录了 URL、属性和 Headers，并且 Http 调用已完全成功。但是，仅删除 block() 调用会导致没有调用，也没有日志：

 // No call made
 final WebClient.ResponseSpec responseSpec = webClient.post()
            .uri(new URI(url + "/tasks/executions"))
            .body(BodyInserters.fromMultipartData(requestParms))
            .exchange();

Answer 1

那是因为它是非阻塞的...

来自 Spring Docs:

Simply put, WebClient is an interface representing the main entry point for performing web requests.

It has been created as a part of the Spring Web Reactive module and will be replacing the classic RestTemplate in these scenarios. The new client is a reactive, non-blocking solution that works over the HTTP/1.1 protocol.

这是一个使用 Reactive Streams concept through the Project Reactor 实现的实现

Spring 5 WebClient 仅在 .exchange() 之后使用 .block() 时进行 Http 调用

Spring 5 WebClient only making Http call when using .block() after .exchange()

spring

spring-webflux