什么是令牌？
对于从低信任环境进行的 API 方法调用，车队引擎要求使用由适当服务账号签名的 JSON Web 令牌 (JWT)。低信任的环境包括智能手机和浏览器。JWT 源自您的服务器，后者是一个完全受信任的环境。JWT 会经过签名和加密，并传递给客户端以供后续与服务器的互动，直到其过期或失效为止。
您的后端应使用标准应用默认凭据机制对 Fleet Engine 进行身份验证和授权。请务必使用由适当服务账号签名的 JWT。如需查看服务账号角色列表，请参阅车队引擎基础知识中的车队引擎服务账号角色。
相反，您的后端应针对 Fleet Engine 进行身份验证和授权 使用标准应用默认凭据 机制。
如需详细了解 JSON Web 令牌，请参阅车队引擎必备知识中的 JSON Web 令牌。
客户端如何获取令牌？
当驾驶员或使用方使用适当的身份验证凭据登录您的应用后，从该设备发出的任何更新都必须使用适当的授权令牌，这些令牌会将应用的权限传达给车队引擎。
作为开发者，您的客户端实现应能够执行以下操作：
- 从您的服务器提取 JSON 网络令牌。
- 在令牌过期之前重复使用该令牌，以尽可能减少令牌刷新次数。
- 在令牌过期时刷新令牌。
GMTDAuthorization 协议会在位置更新时根据 GMTD AuthorizationContext 对象提取 JSON Web 令牌。SDK 必须将令牌与更新信息打包在一起，以便发送到车队引擎。在初始化 SDK 之前，请确保您的服务器端实现可以签发令牌。
如需详细了解 Fleet Engine 预期的令牌，请参阅 为 Fleet Engine 颁发 JSON Web 令牌。
providerID 与 Google Cloud 项目的项目 ID 相同。如需了解如何设置 Google Cloud 项目，请参阅创建 Fleet Engine 项目。
身份验证令牌提取程序示例
以下示例展示了 GMTDAuthorization 的实现
协议。
Swift
import GoogleRidesharingDriver
private let providerURL = "INSERT_YOUR_TOKEN_PROVIDER_URL"
class SampleAccessTokenProvider: NSObject, GMTDAuthorization {
private struct AuthToken {
// The cached vehicle token.
let token: String
// Keep track of when the token expires for caching.
let expiration: TimeInterval
// Keep track of the vehicle ID the cached token is for.
let vehicleID: String
}
enum AccessTokenError: Error {
case missingAuthorizationContext
case missingData
}
private var authToken: AuthToken?
func fetchToken(
with authorizationContext: GMTDAuthorizationContext?,
completion: @escaping GMTDAuthTokenFetchCompletionHandler
) {
// Get the vehicle ID from the authorizationContext. This is set by the Driver SDK.
guard let authorizationContext = authorizationContext else {
completion(nil, AccessTokenError.missingAuthorizationContext)
return
}
let vehicleID = authorizationContext.vehicleID
// If appropriate, use the cached token.
if let authToken = authToken,
authToken.expiration > Date.now.timeIntervalSince1970 && authToken.vehicleID == vehicleID
{
completion(authToken.token, nil)
return
}
// Otherwise, try to fetch a new token from your server.
let request = URLRequest(url: URL(string: providerURL))
let task = URLSession.shared.dataTask(with: request) { [weak self] data, _, error in
guard let strongSelf = self else { return }
guard error == nil else {
completion(nil, error)
return
}
// Replace the following key values with the appropriate keys based on your
// server's expected response.
let vehicleTokenKey = "VEHICLE_TOKEN_KEY"
let tokenExpirationKey = "TOKEN_EXPIRATION"
guard let data = data,
let fetchData = try? JSONSerialization.jsonObject(with: data) as? [String: Any],
let token = fetchData[vehicleTokenKey] as? String,
let expiration = fetchData[tokenExpirationKey] as? Double
else {
completion(nil, AccessTokenError.missingData)
return
}
strongSelf.authToken = AuthToken(
token: token, expiration: expiration, vehicleID: vehicleID)
completion(token, nil)
}
task.resume()
}
}
Objective-C
#import "SampleAccessTokenProvider.h"
#import <GoogleRidesharingDriver/GoogleRidesharingDriver.h>
// SampleAccessTokenProvider.h
@interface SampleAccessTokenProvider : NSObject<GMTDAuthorization>
@end
static NSString *const PROVIDER_URL = @"INSERT_YOUR_TOKEN_PROVIDER_URL";
// SampleAccessTokenProvider.m
@implementation SampleAccessTokenProvider{
// The cached vehicle token.
NSString *_cachedVehicleToken;
// Keep track of the vehicle ID the cached token is for.
NSString *_lastKnownVehicleID;
// Keep track of when tokens expire for caching.
NSTimeInterval _tokenExpiration;
}
- (void)fetchTokenWithContext:(nullable GMTDAuthorizationContext *)authorizationContext
completion:(nonnull GMTDAuthTokenFetchCompletionHandler)completion {
if (!completion) {
NSAssert(NO, @"%s encountered an unexpected nil completion.", __PRETTY_FUNCTION__);
return;
}
// Get the vehicle ID from the authorizationContext. This is set by the Driver SDK.
NSString *vehicleID = authorizationContext.vehicleID;
if (!vehicleID) {
NSAssert(NO, @"Vehicle ID is missing from authorizationContext.");
return;
}
// Clear cached vehicle token if vehicle ID has changed.
if (![_lastKnownVehicleID isEqual:vehicleID]) {
_tokenExpiration = 0.0;
_cachedVehicleToken = nil;
}
_lastKnownVehicleID = vehicleID;
// Clear cached vehicletoken if it has expired.
if ([[NSDate date] timeIntervalSince1970] > _tokenExpiration) {
_cachedVehicleToken = nil;
}
// If appropriate, use the cached token.
if (_cachedVehicleToken) {
completion(_cachedVehicleToken, nil);
return;
}
// Otherwise, try to fetch a new token from your server.
NSURL *requestURL = [NSURL URLWithString:PROVIDER_URL];
NSMutableURLRequest *request =
[[NSMutableURLRequest alloc] initWithURL:requestURL];
request.HTTPMethod = @"GET";
// Replace the following key values with the appropriate keys based on your
// server's expected response.
NSString *vehicleTokenKey = @"VEHICLE_TOKEN_KEY";
NSString *tokenExpirationKey = @"TOKEN_EXPIRATION";
__weak typeof(self) weakSelf = self;
void (^handler)(NSData *_Nullable data, NSURLResponse *_Nullable response,
NSError *_Nullable error) =
^(NSData *_Nullable data, NSURLResponse *_Nullable response, NSError *_Nullable error) {
typeof(self) strongSelf = weakSelf;
if (error) {
completion(nil, error);
return;
}
NSError *JSONError;
NSMutableDictionary *JSONResponse =
[NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:&JSONError];
if (JSONError) {
completion(nil, JSONError);
return;
} else {
// Sample code only. No validation logic.
id expirationData = JSONResponse[tokenExpirationKey];
if ([expirationData isKindOfClass:[NSNumber class]]) {
NSTimeInterval expirationTime = ((NSNumber *)expirationData).doubleValue;
strongSelf->_tokenExpiration = [[NSDate date] timeIntervalSince1970] + expirationTime;
}
strongSelf->_cachedVehicleToken = JSONResponse[vehicleTokenKey];
completion(JSONResponse[vehicleTokenKey], nil);
}
};
NSURLSessionConfiguration *config = [NSURLSessionConfiguration defaultSessionConfiguration];
NSURLSession *mainQueueURLSession =
[NSURLSession sessionWithConfiguration:config delegate:nil
delegateQueue:[NSOperationQueue mainQueue]];
NSURLSessionDataTask *task = [mainQueueURLSession dataTaskWithRequest:request completionHandler:handler];
[task resume];
}
@end