如何設置 RestTemplate 以重試某些響應狀態代碼的調用？

Question

我在設置 RestTemplate 以重試遠程調用時遇到問題。 有誰知道如何配置 RestTemplate 在獲得 503 響應狀態代碼后重試調用？

Answer 1

是的，這是可能的，您可以嘗試自定義重試策略。

class InternalServerExceptionClassifierRetryPolicy extends ExceptionClassifierRetryPolicy {
public InternalServerExceptionClassifierRetryPolicy() {
    final SimpleRetryPolicy simpleRetryPolicy = new SimpleRetryPolicy();
    simpleRetryPolicy.setMaxAttempts(3);

    this.setExceptionClassifier(new Classifier<Throwable, RetryPolicy>() {
        @Override
        public RetryPolicy classify(Throwable classifiable) {
            if (classifiable instanceof HttpServerErrorException) {
                // For 503
                if (((HttpServerErrorException) classifiable).getStatusCode() == HttpStatus.SERVICE_UNAVAILABLE) {
                    return simpleRetryPolicy;
                }
                return new NeverRetryPolicy();
            }
            return new NeverRetryPolicy();
        }
    });
}}

Ans 簡單地稱之為如下：

RetryTemplate template = new RetryTemplate();
template.setRetryPolicy(new InternalServerExceptionClassifierRetryPolicy())

Answer 2

在 catch 塊內重試

try {
    responseEntity = restTemplate.exchange(endpoint, HttpMethod.POST, entity, MyResponse.class);
} catch (HttpClientErrorException hcee) {
    //There is an error in request, if known, improve and retry
} catch (HttpServerErrorException hsee) {
    recvdStatusCode = hsee.getStatusCode();
    // Handle it within a switch case, if there is an option to retry.
}

這可能是另一種方法，我自己從未嘗試過-

@Bean
  public RetryTemplate retryTemplate() {

    int maxAttempt = Integer.parseInt(env.getProperty("maxAttempt"));
    int retryTimeInterval = Integer.parseInt(env.getProperty("retryTimeInterval"));

    SimpleRetryPolicy retryPolicy = new SimpleRetryPolicy();
    retryPolicy.setMaxAttempts(maxAttempt);

    FixedBackOffPolicy backOffPolicy = new FixedBackOffPolicy();
    backOffPolicy.setBackOffPeriod(retryTimeInterval); // 1.5 seconds

    RetryTemplate template = new RetryTemplate();
    template.setRetryPolicy(retryPolicy);
    template.setBackOffPolicy(backOffPolicy);

    return template;
  }

//這里是調用-

retryTemplate.execute(context -> {
        System.out.println("inside retry method");
        ResponseEntity<?> requestData = RestTemplateProvider.getInstance().postAsNewRequest(bundle, ServiceResponse.class, serivceURL,
                CommonUtils.getHeader("APP_Name"));

        _LOGGER.info("Response ..."+ requestData);
            throw new IllegalStateException("Something went wrong");
        });