iOS Swift应用从旧版FCM API迁移至HTTP v1的方法咨询

核心差异说明 #

旧版FCM API使用serverKey直接授权，HTTP v1版本则需要通过OAuth 2.0访问令牌完成身份验证，同时请求URL、请求体结构均有变更。

迁移步骤与代码实现 #

1. 准备服务账号密钥 #

从Firebase控制台下载服务账号JSON文件：

• 进入项目设置 → 服务账号 → 生成新的私钥，保存JSON文件到项目中（注意：客户端存储私钥存在安全风险，生产环境建议将发送逻辑移至后端）。

2. 实现访问令牌生成函数 #

HTTP v1需要Bearer令牌，需通过服务账号的私钥生成JWT并换取访问令牌：

import Foundation
import CryptoKit

func getFCMAccessToken(serviceAccountJSON: [String: Any]) async throws -> String {
    guard let privateKey = serviceAccountJSON["private_key"] as? String,
          let clientEmail = serviceAccountJSON["client_email"] as? String else {
        throw NSError(domain: "FCM", code: -1, userInfo: [NSLocalizedDescriptionKey: "Invalid service account data"])
    }
    let tokenURL = "https://oauth2.googleapis.com/token"
    
    // 构建JWT头部
    let header = ["alg": "RS256", "typ": "JWT"]
    let headerBase64 = try JSONSerialization.data(withJSONObject: header)
        .base64EncodedString(options: .endLineWithLineFeed)
    
    // 构建JWT Payload
    let now = Date().timeIntervalSince1970
    let payload = [
        "iss": clientEmail,
        "scope": "https://www.googleapis.com/auth/firebase.messaging",
        "aud": tokenURL,
        "exp": now + 3600, // 令牌有效期1小时，建议缓存复用
        "iat": now
    ]
    let payloadBase64 = try JSONSerialization.data(withJSONObject: payload)
        .base64EncodedString(options: .endLineWithLineFeed)
    
    // 生成签名
    let signatureInput = "\(headerBase64).\(payloadBase64)"
    let cleanedPrivateKey = privateKey.replacingOccurrences(of: "-----BEGIN PRIVATE KEY-----\n", with: "")
        .replacingOccurrences(of: "\n-----END PRIVATE KEY-----", with: "")
    guard let signer = try? P256.Signing.PrivateKey(pemRepresentation: privateKey) else {
        throw NSError(domain: "FCM", code: -2, userInfo: [NSLocalizedDescriptionKey: "Failed to load private key"])
    }
    let signature = try signer.signature(for: signatureInput.data(using: .utf8)!)
    let signatureBase64 = signature.rawRepresentation.base64EncodedString(options: .endLineWithLineFeed)
    
    // 组装JWT并请求访问令牌
    let jwt = "\(headerBase64).\(payloadBase64).\(signatureBase64)"
    var request = URLRequest(url: URL(string: tokenURL)!)
    request.httpMethod = "POST"
    request.setValue("application/x-www-form-urlencoded", forHTTPHeaderField: "Content-Type")
    request.httpBody = "grant_type=urn:ietf:params:oauth:grant-type:jwt-bearer&assertion=\(jwt)".data(using: .utf8)
    
    let (data, _) = try await URLSession.shared.data(for: request)
    guard let tokenResponse = try JSONSerialization.jsonObject(with: data) as? [String: Any],
          let accessToken = tokenResponse["access_token"] as? String else {
        throw NSError(domain: "FCM", code: -3, userInfo: [NSLocalizedDescriptionKey: "Failed to get access token"])
    }
    return accessToken
}

3. 重构通知发送逻辑 #

更新请求URL与请求体结构，适配v1 API规范：

func sendFCMNotification(token: String, title: String, body: String, serviceAccountJSON: [String: Any]) async throws {
    guard let projectID = serviceAccountJSON["project_id"] as? String,
          let url = URL(string: "https://fcm.googleapis.com/v1/projects/\(projectID)/messages:send") else {
        throw NSError(domain: "FCM", code: -1, userInfo: [NSLocalizedDescriptionKey: "Invalid project ID or URL"])
    }
    
    // 获取访问令牌
    let accessToken = try await getFCMAccessToken(serviceAccountJSON: serviceAccountJSON)
    
    // 构建v1格式的请求体
    let message: [String: Any] = [
        "token": token,
        "notification": [
            "title": title,
            "body": body
        ],
        "apns": [
            "headers": [
                "apns-priority": "10" // 对应iOS高优先级通知
            ]
        ]
    ]
    let requestBody = try JSONSerialization.data(withJSONObject: ["message": message])
    
    var request = URLRequest(url: url)
    request.httpMethod = "POST"
    request.httpBody = requestBody
    request.setValue("application/json", forHTTPHeaderField: "Content-Type")
    request.setValue("Bearer \(accessToken)", forHTTPHeaderField: "Authorization")
    
    let (data, response) = try await URLSession.shared.data(for: request)
    
    // 处理响应
    if let httpResponse = response as? HTTPURLResponse, httpResponse.statusCode != 200 {
        let errorDetails = try JSONSerialization.jsonObject(with: data) as? [String: Any]
        let errorMessage = errorDetails?["error"]?["message"] as? String ?? "Unknown error"
        throw NSError(domain: "FCM", code: httpResponse.statusCode, userInfo: [NSLocalizedDescriptionKey: errorMessage])
    }
    
    let responseDict = try JSONSerialization.jsonObject(with: data) as! [String: Any]
    print("FCM发送成功，响应：\(responseDict)")
}

4. 使用示例 #

读取服务账号JSON并调用发送函数：

// 读取服务账号JSON文件
guard let jsonPath = Bundle.main.path(forResource: "your-service-account", ofType: "json"),
      let jsonData = try? Data(contentsOf: URL(fileURLWithPath: jsonPath)),
      let serviceAccountJSON = try? JSONSerialization.jsonObject(with: jsonData) as? [String: Any] else {
    fatalError("无法加载服务账号JSON文件")
}

// 发送通知示例
Task {
    do {
        try await sendFCMNotification(
            token: "目标设备令牌",
            title: "测试标题",
            body: "测试内容",
            serviceAccountJSON: serviceAccountJSON
        )
    } catch {
        print("发送失败：\(error.localizedDescription)")
    }
}

关键注意事项 #

• 令牌缓存：访问令牌有效期为1小时，建议缓存令牌避免重复生成，提升性能。
• 权限配置：确保服务账号拥有Cloud Messaging Admin角色，否则会返回权限不足错误。
• 安全提示：客户端存储私钥存在泄露风险，生产环境建议将FCM发送逻辑部署在后端服务器。

内容的提问来源于stack exchange，提问作者Taimoor Arif