Spring - 如果服务返回 409 HTTP 代码，则重试请求

在使用Spring框架开发应用程序时，我们经常会遇到与外部服务进行交互的情况。在这些交互中，有时候我们的请求可能会返回409 HTTP代码，这意味着请求冲突，即所请求的资源与服务器上的当前状态不匹配。为了处理这种情况，我们可以选择重试请求，以便获得正确的响应。

java
import org.springframework.http.HttpMethod;
import org.springframework.http.ResponseEntity;
import org.springframework.web.client.HttpClientErrorException;
import org.springframework.web.client.RestTemplate;
public class RetryRequestExample {
    private static final int MAX_RETRIES = 3;
    private static final long RETRY_DELAY = 1000;
    public static void main(String[] args) {
        RestTemplate restTemplate = new RestTemplate();
        String url = "http://example.com/api/resource";
        int retries = 0;
        boolean success = false;
        while (retries < MAX_RETRIES && !success) {
            try {
                ResponseEntity response = restTemplate.exchange(url, HttpMethod.GET, null, String.class);
                success = true;
                System.out.println("Request successful!");
            } catch (HttpClientErrorException.Conflict e) {
                retries++;
                System.out.println("Request conflict, retrying...");
                try {
                    Thread.sleep(RETRY_DELAY);
                } catch (InterruptedException ex) {
                    ex.printStackTrace();
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        if (!success) {
            System.out.println("Request failed after " + MAX_RETRIES + " retries.");
        }
    }
}