什么是无效的单声道值无效的方法？

Question

我会尽力解释我的用例。在我的应用程序中调用外部Web服务之前，我请使用Spring WebFlux WebClient向代币提供商提供OAuth访问令牌，并且我正在缓存该值，以便下次需要它。每当请求失败使用错误代码401时，我都想用新令牌重试缓存并重试。

一切正常，接受我不确定单声道的缓存无效。

如果需要使缓存无效，则将存储在布尔变量中是个好主意吗？在订阅Auth Mono时重试时，无效的缓存谓词将是正确的，这将无效缓存，并将完成新的请求。

还有其他想法吗？

示例代码：

@Component
public class AccessTokenService {

    private final WebClient accessTokenClient;
    private final Mono<Token> accessTokenMono;
    private final AtomicBoolean cacheInvalidated = new AtomicBoolean();

    public AccessTokenService() {
        accessTokenClient = WebClient.builder()
                .baseUrl("example-token-uri")
                .build();

        accessTokenMono = initAccessTokenMono();
    }

    private Mono<Token> initAccessTokenMono() {
        return accessTokenClient.post()
                .uri(uriBuilder -> uriBuilder
                        // Some credentials as parameters
                        .build())
                .retrieve()
                .bodyToMono(Token.class)
                // Always set cache invalidated to false when we get the response
                .doOnSuccess(token -> cacheInvalidated.set(false))
                .cacheInvalidateIf(accessToken -> cacheInvalidated.get());
    }

    public Mono<Token> getAccessTokenMono() {
        // Shared for all requests
        return accessTokenMono;
    }

// Called on 401
    public void setCacheInvalidated() {
        // Sets the predicate to true. For the next subscription the cache will be invalidated and a new request to the token provider will occur
        cacheInvalidated.set(true);
    }
}

Answer 1

与其尝试将肮脏标志的状态与mono的有效性保持同步，为什么不在检测401时简单地交换新的mono？我还通过cache（）定期刷新令牌，但这并不是您尝试做的事情。

@Component
public class AccessTokenService {
    private static final Duration TOKEN_REFRESH_INTERVAL = Duration.ofHours(1);
    private final WebClient accessTokenClient;
    private final AtomicReference<Mono<Token>> accessTokenMono = new AtomicReference<>();

    public AccessTokenService() {
        accessTokenClient = WebClient.builder()
            .baseUrl("example-token-uri")
            .build();

        accessTokenMono.set(initAccessTokenMono());
    }

    private Mono<Token> initAccessTokenMono() {
        return accessTokenClient.post()
            .uri(uriBuilder -> uriBuilder
                // Some credentials as parameters
                .build())
            .retrieve()
            .bodyToMono(Token.class)
            .cache(token -> TOKEN_REFRESH_INTERVAL,         // refresh every interval
                exc -> Duration.ZERO, () -> Duration.ZERO); // don't cache exceptions or empties
    }

    public Mono<Token> getAccessTokenMono() {
        // Shared for all requests
        return accessTokenMono.get();
    }

    // Called on 401
    public void setCacheInvalidated() {
        // Plug in a new Mono so subsequent requests get a new token
        accessTokenMono.set(initAccessTokenMono());
    }
}