Android 使用 Retrofit 刷新 OAuth 令牌而不修改所有调用

请不要使用Interceptors来处理身份验证.

目前，处理身份验证的最佳方法是使用专门为this purpose设计的新的AuthenticatorAPI.

当响应为401 Not Authorised retrying last failed request时，OkHttp将为Authenticator提供凭据.

public class TokenAuthenticator implements Authenticator {
    @Override
    public Request authenticate(Proxy proxy, Response response) throws IOException {
        // Refresh your access_token using a synchronous api request
        newAccessToken = service.refreshToken();

        // Add new header to rejected request and retry it
        return response.request().newBuilder()
                .header(AUTHORIZATION, newAccessToken)
                .build();
    }

    @Override
    public Request authenticateProxy(Proxy proxy, Response response) throws IOException {
        // Null indicates no attempt to authenticate.
        return null;
    }

将Authenticator连接到OkHttpClient，方法与Interceptors相同

OkHttpClient okHttpClient = new OkHttpClient();
okHttpClient.setAuthenticator(authAuthenticator);

创建Retrofit RestAdapter时使用此客户端

RestAdapter restAdapter = new RestAdapter.Builder()
                .setEndpoint(ENDPOINT)
                .setClient(new OkClient(okHttpClient))
                .build();
return restAdapter.create(API.class);