什么是令牌？
对于从低信任环境进行的 API 方法调用，Fleet Engine 需要使用由相应服务账号签名的 JSON Web 令牌 (JWT)。低信任的环境包括智能手机和浏览器。JWT 来自您的服务器，这是一个完全可信的环境。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。请务必使用由相应服务账号签名的 JWT。如需查看服务账号角色的列表，请参阅 Fleet Engine 基础知识中的 Fleet Engine 服务账号角色。
相反，您的后端应使用标准应用默认凭据机制针对 Fleet Engine 进行身份验证和授权。
如需详细了解 JSON Web 令牌，请参阅 Fleet Engine 基础知识中的 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，您的客户端实现应提供执行以下操作的能力：
- 从您的服务器提取 JSON 网络令牌。
- 在令牌过期之前重复使用，以最大限度地减少令牌刷新。
- 在令牌过期时刷新。
GMTDAuthorization 协议会在位置信息更新时根据 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，以发送到 Fleet Engine。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。
身份验证令牌提取器示例
以下示例实现了授权令牌提供程序：
Swift
/*
* SampleAccessTokenProvider.swift
*/
import GoogleRidesharingConsumer
private let providerURL = "INSERT_YOUR_TOKEN_PROVIDER_URL"
class SampleAccessTokenProvider: NSObject, GMTCAuthorization {
private struct AuthToken {
// The cached trip token.
let token: String
// Keep track of when the token expires for caching.
let expiration: TimeInterval
// Keep track of the trip ID the cached token is for.
let tripID: String
}
enum AccessTokenError: Error {
case missingAuthorizationContext
case missingData
}
private var authToken: AuthToken?
func fetchToken(
with authorizationContext: GMTCAuthorizationContext?,
completion: @escaping GMTCAuthTokenFetchCompletionHandler
) {
// Get the trip ID from the authorizationContext. This is set by the Consumer SDK.
guard let authorizationContext = authorizationContext else {
completion(nil, AccessTokenError.missingAuthorizationContext)
return
}
let tripID = authorizationContext.tripID
// If appropriate, use the cached token.
if let authToken = authToken,
authToken.expiration > Date.now.timeIntervalSince1970 && authToken.tripID == tripID
{
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 tripTokenKey = "TRIP_TOKEN_KEY"
let tokenExpirationKey = "TOKEN_EXPIRATION"
guard let data = data,
let fetchData = try? JSONSerialization.jsonObject(with: data) as? [String: Any],
let token = fetchData[tripTokenKey] as? String,
let expiration = fetchData[tokenExpirationKey] as? Double
else {
completion(nil, AccessTokenError.missingData)
return
}
strongSelf.authToken = AuthToken(token: token, expiration: expiration, tripID: tripID)
completion(token, nil)
}
task.resume()
}
}
Objective-C
/*
* SampleAccessTokenProvider.h
*/
#import <Foundation/Foundation.h>
#import <GoogleRidesharingConsumer/GoogleRidesharingConsumer.h>
NS_ASSUME_NONNULL_BEGIN
@interface SampleAccessTokenProvider : NSObject <GMTCAuthorization>
@end
NS_ASSUME_NONNULL_END
/*
* SampleAccessTokenProvider.m
*/
#import "SampleAccessTokenProvider.h"
#import "GoogleRidesharingConsumer/GoogleRidesharingConsumer.h"
static NSString *const PROVIDER_URL = @"INSERT_YOUR_TOKEN_PROVIDER_URL";
// SampleAccessTokenProvider.m
@implementation SampleAccessTokenProvider {
// The cached token with claims to the current trip.
NSString *_cachedTripToken;
// Keep track of the Trip ID the cached token is for.
NSString *_lastKnownTripID;
// Keep track of when tokens expire for caching.
NSTimeInterval _tokenExpiration;
}
- (void)fetchTokenWithContext:(nullable GMTCAuthorizationContext *)authorizationContext
completion:(nonnull GMTCAuthTokenFetchCompletionHandler)completion {
// Get the trip ID from the authorizationContext. This is set by the Consumer SDK.
NSString *tripID = authorizationContext.tripID;
// Clear cached trip token if trip ID has changed.
if (![_lastKnownTripID isEqual:tripID]) {
_tokenExpiration = 0.0;
_cachedTripToken = nil;
}
_lastKnownTripID = tripID;
// Clear cached tripToken if it has expired.
if ([[NSDate date] timeIntervalSince1970] > _tokenExpiration) {
_cachedTripToken = nil;
}
// If appropriate, use the cached token.
if (_cachedTripToken) {
completion(_cachedTripToken, 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 *tripTokenKey = @"TRIP_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->_cachedTripToken = JSONResponse[tripTokenKey];
completion(JSONResponse[tripTokenKey], 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