Question

如果发生错误，我希望通过以下方法引发自定义异常：

@Service
public class MyClass {

    private final WebClient webClient;

    public MatcherClient(@Value("${my.url}") final String myUrl) {
        this.webClient = WebClient.create(myUrl);
    }

    public void sendAsync(String request) {

        Mono<MyCustomResponse> result = webClient.post()
            .header(HttpHeaders.CONTENT_TYPE, "application/json")
            .body(BodyInserters.fromObject(request))
            .retrieve()
            .doOnError(throwable -> throw new CustomException(throwable.getMessage()))
            .subscribe(response -> log.info(response));

    }

}

我还设置了一个单元测试，期望抛出CustomException。不幸的是，测试失败，并且Exception被包装到Mono对象中。这里还有测试代码供参考：

@Test(expected = CustomException.class)
public void testSendAsyncRethrowingException() {
    MockResponse mockResponse = new MockResponse()
        .setHeader(HttpHeaders.CONTENT_TYPE, "application/json")
        .setResponseCode(500).setBody("Server error");
    mockWebServer.enqueue(mockResponse);

    matcherService.matchAsync(track);
}

我正在使用MockWebServer模拟测试中的错误。

那么，如果要使我的方法真正引发异常，该调用该如何实现doOnError或onError部分？

Answer 1

我建议公开一个反应式API，该API从Web客户端返回Mono<Void>，尤其是如果您将方法命名为“ sendAsync”。如果您必须阻止调用返回/失败，则它不是异步的。如果您想提供sendSync()的替代方案，则可以随时将其称为sendAsync().block()。

对于异常的转换，可以使用专用的onErrorMap运算符。

对于测试而言，事实是，您不能100％使用纯命令性和同步结构（例如JUnit的Test(expected=?)批注）测试异步代码。（尽管 some 反应性运算符不会引起并行性，所以这种测试有时有时可以正常工作）。

您还可以在此处使用.block()（测试是其中不太可能出现问题的罕见情况之一。）

但是如果我是你，我会养成使用StepVerifier中的reactor-test的习惯。举一个总结我的建议的例子：

@Service public class MyClass { private final WebClient webClient; public MatcherClient(@Value("${my.url}") final String myUrl) { this.webClient = WebClient.create(myUrl); } public Mono<MyCustomResponse> sendAsync(String request) { return webClient.post() .header(HttpHeaders.CONTENT_TYPE, "application/json") .body(BodyInserters.fromObject(request)) .retrieve() .onErrorMap(throwable -> new CustomException(throwable.getMessage())) //if you really need to hardcode that logging //(can also be done by users who decide to subscribe or further add operators) .doOnNext(response -> log.info(response)); } }

和测试：

@Test(expected = CustomException.class) public void testSendAsyncRethrowingException() { MockResponse mockResponse = new MockResponse() .setHeader(HttpHeaders.CONTENT_TYPE, "application/json") .setResponseCode(500).setBody("Server error"); mockWebServer.enqueue(mockResponse); //Monos are generally lazy, so the code below doesn't trigger any HTTP request yet Mono<MyCustomResponse> underTest = matcherService.matchAsync(track); StepVerifier.create(underTest) .expectErrorSatisfies(t -> assertThat(t).isInstanceOf(CustomException.class) .hasMessage(throwable.getMessage()) ) .verify(); //this triggers the Mono, compares the //signals to the expectations/assertions and wait for mono's completion }

Answer 2

<块引用>

WebClient 中的retrieve() 方法抛出WebClientResponseException 每当收到状态代码为 4xx 或 5xx 的响应时。

1.您可以使用 onStatus() 方法自定义异常

public Mono<JSONObject> listGithubRepositories() {
 return webClient.get()
        .uri(URL)
        .retrieve()
        .onStatus(HttpStatus::is4xxClientError, clientResponse ->
            Mono.error(new MyCustomClientException())
        )
        .onStatus(HttpStatus::is5xxServerError, clientResponse ->
            Mono.error(new MyCustomServerException())
        )
        .bodyToMono(JSONObject.class);
}

2.通过检查响应状态抛出自定义异常

   Mono<Object> result = webClient.get().uri(URL).exchange().log().flatMap(entity -> {
        HttpStatus statusCode = entity.statusCode();
        if (statusCode.is4xxClientError() || statusCode.is5xxServerError())
        {
            return Mono.error(new Exception(statusCode.toString()));
        }
        return Mono.just(entity);
    }).flatMap(clientResponse -> clientResponse.bodyToMono(JSONObject.class))

参考： https://www.callicoder.com/spring-5-reactive-webclient-webtestclient-examples/

Answer 3

我不再使用doOnError，而是订阅方法也接受错误使用者：

Mono<MyCustomResponse> result = webClient.post()
            .header(HttpHeaders.CONTENT_TYPE, "application/json")
            .body(BodyInserters.fromObject(request))
            .retrieve()
            .subscribe(response -> log.info(response),
                       throwable -> throw new CustomException(throwable.getMessage()));

该文档对您有很大帮助：https://projectreactor.io/docs/core/release/reference/index.html#_error_handling_operators

如何在响应式Spring WebClient调用的错误部分抛出异常？

3 个答案: