Android OkHttp，刷新过期 token

Question

场景:我正在使用 OkHttp/Retrofit 访问网络服务:同时发送多个 HTTP 请求。在某个时候，授权 token 会过期，多个请求将收到 401 响应。

问题:在我的第一个实现中，我使用了一个拦截器(此处已简化)并且每个线程都尝试刷新 token 。这会导致一团糟。

public class SignedRequestInterceptor implements Interceptor {

    @Override
    public Response intercept(Chain chain) throws IOException {
        Request request = chain.request();

        // 1. sign this request
        request = request.newBuilder()
                    .header(AUTH_HEADER_KEY, BEARER_HEADER_VALUE + token)
                    .build();


        // 2. proceed with the request
        Response response = chain.proceed(request);

        // 3. check the response: have we got a 401?
        if (response.code() == HttpURLConnection.HTTP_UNAUTHORIZED) {

            // ... try to refresh the token
            newToken = mAuthService.refreshAccessToken(..);


            // sign the request with the new token and proceed
            Request newRequest = request.newBuilder()
                                .removeHeader(AUTH_HEADER_KEY)
                                .addHeader(AUTH_HEADER_KEY, BEARER_HEADER_VALUE + newToken.getAccessToken())
                                .build();

            // return the outcome of the newly signed request
            response = chain.proceed(newRequest);

        }

        return response;
    }
}

所需的解决方案:所有线程都应等待一个 token 刷新:第一个失败的请求触发刷新，并与其他请求一起等待新 token 。

处理此问题的好方法是什么？ OkHttp 的一些内置功能(如 Authenticator)有帮助吗？感谢您的任何提示。

Answer 1

我遇到了同样的问题，我设法使用 ReentrantLock 解决了它.

import java.io.IOException;
import java.net.HttpURLConnection;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

import okhttp3.Interceptor;
import okhttp3.Request;
import okhttp3.Response;
import timber.log.Timber;

public class RefreshTokenInterceptor implements Interceptor {

    private Lock lock = new ReentrantLock();

    @Override
    public Response intercept(Interceptor.Chain chain) throws IOException {

        Request request = chain.request();
        Response response = chain.proceed(request);

        if (response.code() == HttpURLConnection.HTTP_UNAUTHORIZED) {

            // first thread will acquire the lock and start the refresh token
            if (lock.tryLock()) {
                Timber.i("refresh token thread holds the lock");

                try {
                    // this sync call will refresh the token and save it for 
                    // later use (e.g. sharedPreferences)
                    authenticationService.refreshTokenSync();
                    Request newRequest = recreateRequestWithNewAccessToken(chain);
                    return chain.proceed(newRequest);
                } catch (ServiceException exception) {
                    // depending on what you need to do you can logout the user at this 
                    // point or throw an exception and handle it in your onFailure callback
                    return response;
                } finally {
                    Timber.i("refresh token finished. release lock");
                    lock.unlock();
                }

            } else {
                Timber.i("wait for token to be refreshed");
                lock.lock(); // this will block the thread until the thread that is refreshing 
                             // the token will call .unlock() method
                lock.unlock();
                Timber.i("token refreshed. retry request");
                Request newRequest = recreateRequestWithNewAccessToken(chain);
                return chain.proceed(newRequest);
            }
        } else {
            return response;
        }
    }

    private Request recreateRequestWithNewAccessToken(Chain chain) {
        String freshAccessToken = sharedPreferences.getAccessToken();
        Timber.d("[freshAccessToken] %s", freshAccessToken);
        return chain.request().newBuilder()
                .header("access_token", freshAccessToken)
                .build();
    }
}

使用此解决方案的主要优点是您可以使用 mockito 编写单元测试并对其进行测试。您将必须启用 Mockito 孵化功能以模拟 final类(来自 okhttp 的响应)。阅读更多关于 here 的信息.测试看起来像这样:

@RunWith(MockitoJUnitRunner.class)
public class RefreshTokenInterceptorTest {

    private static final String FRESH_ACCESS_TOKEN = "fresh_access_token";

    @Mock
    AuthenticationService authenticationService;

    @Mock
    RefreshTokenStorage refreshTokenStorage;

    @Mock
    Interceptor.Chain chain;

    @BeforeClass
    public static void setup() {
        Timber.plant(new Timber.DebugTree() {

            @Override
            protected void log(int priority, String tag, String message, Throwable t) {
                System.out.println(Thread.currentThread() + " " + message);
            }
        });
    }

    @Test
    public void refreshTokenInterceptor_works_as_expected() throws IOException, InterruptedException {

        Response unauthorizedResponse = createUnauthorizedResponse();
        when(chain.proceed((Request) any())).thenReturn(unauthorizedResponse);
        when(authenticationService.refreshTokenSync()).thenAnswer(new Answer<Boolean>() {
            @Override
            public Boolean answer(InvocationOnMock invocation) throws Throwable {
                //refresh token takes some time
                Thread.sleep(10);
                return true;
            }
        });
        when(refreshTokenStorage.getAccessToken()).thenReturn(FRESH_ACCESS_TOKEN);
        Request fakeRequest = createFakeRequest();
        when(chain.request()).thenReturn(fakeRequest);

        final Interceptor interceptor = new RefreshTokenInterceptor(authenticationService, refreshTokenStorage);

        Timber.d("5 requests try to refresh token at the same time");
        final CountDownLatch countDownLatch5 = new CountDownLatch(5);
        for (int i = 0; i < 5; i++) {
            new Thread(new Runnable() {
                @Override
                public void run() {
                    try {
                        interceptor.intercept(chain);
                        countDownLatch5.countDown();
                    } catch (IOException e) {
                        throw new RuntimeException(e);
                    }
                }
            }).start();
        }
        countDownLatch5.await();

        verify(authenticationService, times(1)).refreshTokenSync();


        Timber.d("next time another 3 threads try to refresh the token at the same time");
        final CountDownLatch countDownLatch3 = new CountDownLatch(3);
        for (int i = 0; i < 3; i++) {
            new Thread(new Runnable() {
                @Override
                public void run() {
                    try {
                        interceptor.intercept(chain);
                        countDownLatch3.countDown();
                    } catch (IOException e) {
                        throw new RuntimeException(e);
                    }
                }
            }).start();
        }
        countDownLatch3.await();

        verify(authenticationService, times(2)).refreshTokenSync();


        Timber.d("1 thread tries to refresh the token");
        interceptor.intercept(chain);

        verify(authenticationService, times(3)).refreshTokenSync();
    }

    private Response createUnauthorizedResponse() throws IOException {
        Response response = mock(Response.class);
        when(response.code()).thenReturn(401);
        return response;
    }

    private Request createFakeRequest() {
        Request request = mock(Request.class);
        Request.Builder fakeBuilder = createFakeBuilder();
        when(request.newBuilder()).thenReturn(fakeBuilder);
        return request;
    }

    private Request.Builder createFakeBuilder() {
        Request.Builder mockBuilder = mock(Request.Builder.class);
        when(mockBuilder.header("access_token", FRESH_ACCESS_TOKEN)).thenReturn(mockBuilder);
        return mockBuilder;
    }

}