Supabase云同步架构：Flutter应用的数据同步策略
Supabase云同步架构：Flutter应用的数据同步策略本文基于BeeCount(蜜蜂记账)项目的实际开发经验，深入探讨如何使用Supabase构建安全、高效的云端数据同步系统。
项目背景
BeeCount(蜜蜂记账)是一款开源、简洁、无广告的个人记账应用。所有财务数据完全由用户掌控，支持本地存储和可选的云端同步，确保数据绝对安全。
引言
在现代移动应用开发中，多设备数据同步已成为用户的基本需求。用户希望在手机、平板、不同设备间无缝切换，同时保持数据的一致性和安全性。BeeCount选择Supabase作为云端后台服务，不仅因为其开源特性和强大功能，更重要的是它提供了完整的数据安全保障。
Supabase架构优势
开源与自主可控
[*]开源透明：完全开源的后台即服务(BaaS)解决方案
[*]数据主权：支持自建部署，数据完全可控
[*]标准技术：基于PostgreSQL，无厂商锁定风险
功能完整性
[*]实时数据库：基于PostgreSQL的实时数据同步
[*]用户认证：完整的身份验证和授权系统
[*]文件存储：对象存储服务，支持大文件上传
[*]边缘函数：服务端逻辑处理能力
同步架构设计
整体架构图
┌─────────────────┐ ┌──────────────────┐ ┌─────────────────┐
│ Flutter App │ │ Supabase │ │ Other Device│
│(Local SQLite) │◄──►│(PostgreSQL) │◄──►│(Local SQLite) │
│ │ │(Auth + Storage) │ │ │
└─────────────────┘ └──────────────────┘ └─────────────────┘
│ │ │
└───── 加密备份文件 ─────┴───── 加密备份文件 ─────┘核心设计原则
[*]本地优先：所有操作优先在本地完成，确保响应速度
[*]增量同步：只同步变更数据，降低网络开销
[*]端到端加密：敏感数据在客户端加密后上传
[*]冲突处理：合理的冲突解决策略
[*]离线可用：网络异常时应用仍可正常使用
认证系统集成
Supabase认证配置
class SupabaseAuthService implements AuthService {
final s.SupabaseClient client;
SupabaseAuthService({required this.client});
@override
Future signInWithEmail({
required String email,
required String password,
}) async {
try {
final response = await client.auth.signInWithPassword(
email: email,
password: password,
);
if (response.user != null) {
return AuthResult.success(user: AppUser.fromSupabase(response.user!));
} else {
return AuthResult.failure(error: 'Login failed');
}
} catch (e) {
return AuthResult.failure(error: e.toString());
}
}
@override
Future signUpWithEmail({
required String email,
required String password,
}) async {
try {
final response = await client.auth.signUp(
email: email,
password: password,
);
return AuthResult.success(user: AppUser.fromSupabase(response.user!));
} catch (e) {
return AuthResult.failure(error: e.toString());
}
}
@override
Stream get authStateChanges {
return client.auth.onAuthStateChange.map((data) {
if (data.session?.user != null) {
return AuthState.authenticated(
user: AppUser.fromSupabase(data.session!.user)
);
}
return AuthState.unauthenticated();
});
}
}用户模型设计
class AppUser {
final String id;
final String email;
final DateTime? lastSignInAt;
const AppUser({
required this.id,
required this.email,
this.lastSignInAt,
});
factory AppUser.fromSupabase(s.User user) {
return AppUser(
id: user.id,
email: user.email ?? '',
lastSignInAt: user.lastSignInAt,
);
}
bool get isAnonymous => email.isEmpty;
}数据同步策略
备份文件格式
BeeCount采用加密备份文件的方式进行数据同步：
class BackupData {
final String version;
final DateTime createdAt;
final String deviceId;
final Map<String, dynamic> ledgers;
final Map<String, dynamic> accounts;
final Map<String, dynamic> categories;
final Map<String, dynamic> transactions;
BackupData({
required this.version,
required this.createdAt,
required this.deviceId,
required this.ledgers,
required this.accounts,
required this.categories,
required this.transactions,
});
Map<String, dynamic> toJson() => {
'version': version,
'createdAt': createdAt.toIso8601String(),
'deviceId': deviceId,
'ledgers': ledgers,
'accounts': accounts,
'categories': categories,
'transactions': transactions,
};
factory BackupData.fromJson(Map<String, dynamic> json) {
return BackupData(
version: json['version'],
createdAt: DateTime.parse(json['createdAt']),
deviceId: json['deviceId'],
ledgers: json['ledgers'],
accounts: json['accounts'],
categories: json['categories'],
transactions: json['transactions'],
);
}
}同步服务实现
class SupabaseSyncService implements SyncService {
final s.SupabaseClient client;
final BeeDatabase db;
final BeeRepository repo;
final AuthService auth;
final String bucket;
// 状态缓存和上传窗口管理
final Map<int, SyncStatus> _statusCache = {};
final Map<int, _RecentUpload> _recentUpload = {};
final Map<int, DateTime> _recentLocalChangeAt = {};
SupabaseSyncService({
required this.client,
required this.db,
required this.repo,
required this.auth,
this.bucket = 'beecount-backups',
});
@override
Future<SyncStatus> getSyncStatus(int ledgerId) async {
// 检查缓存
if (_statusCache.containsKey(ledgerId)) {
final cached = _statusCache!;
if (DateTime.now().difference(cached.lastCheck).inMinutes < 5) {
return cached;
}
}
try {
final user = await auth.getCurrentUser();
if (user == null) {
return SyncStatus.notLoggedIn();
}
// 获取云端文件信息
final fileName = 'ledger_${ledgerId}_backup.json';
final cloudFile = await _getCloudFileInfo(fileName);
// 计算本地数据指纹
final localFingerprint = await _calculateLocalFingerprint(ledgerId);
if (cloudFile == null) {
final status = SyncStatus.localOnly(
localFingerprint: localFingerprint,
hasLocalChanges: true,
);
_statusCache = status;
return status;
}
// 比较指纹判断同步状态
final isUpToDate = localFingerprint == cloudFile.fingerprint;
final status = SyncStatus.synced(
localFingerprint: localFingerprint,
cloudFingerprint: cloudFile.fingerprint,
isUpToDate: isUpToDate,
lastSyncAt: cloudFile.lastModified,
);
_statusCache = status;
return status;
} catch (e) {
logger.error('Failed to get sync status', e);
return SyncStatus.error(error: e.toString());
}
}
@override
Future<SyncResult> uploadBackup(int ledgerId) async {
try {
final user = await auth.getCurrentUser();
if (user == null) {
return SyncResult.failure(error: 'Not logged in');
}
// 生成备份数据
final backupData = await _generateBackup(ledgerId);
final jsonString = json.encode(backupData.toJson());
// 加密备份数据
final encryptedData = await _encryptBackupData(jsonString);
// 上传到Supabase Storage
final fileName = 'ledger_${ledgerId}_backup.json';
final uploadResult = await client.storage
.from(bucket)
.uploadBinary(fileName, encryptedData);
if (uploadResult.isNotEmpty) {
// 记录上传成功
final fingerprint = await _calculateLocalFingerprint(ledgerId);
_recentUpload = _RecentUpload(
fingerprint: fingerprint,
uploadedAt: DateTime.now(),
);
// 更新缓存
_statusCache = SyncStatus.synced(
localFingerprint: fingerprint,
cloudFingerprint: fingerprint,
isUpToDate: true,
lastSyncAt: DateTime.now(),
);
return SyncResult.success(
syncedAt: DateTime.now(),
message: 'Backup uploaded successfully',
);
}
return SyncResult.failure(error: 'Upload failed');
} catch (e) {
logger.error('Failed to upload backup', e);
return SyncResult.failure(error: e.toString());
}
}
@override
Future<SyncResult> downloadRestore(int ledgerId) async {
try {
final user = await auth.getCurrentUser();
if (user == null) {
return SyncResult.failure(error: 'Not logged in');
}
// 下载备份文件
final fileName = 'ledger_${ledgerId}_backup.json';
final downloadData = await client.storage
.from(bucket)
.download(fileName);
if (downloadData.isEmpty) {
return SyncResult.failure(error: 'No backup found');
}
// 解密备份数据
final decryptedData = await _decryptBackupData(downloadData);
final backupData = BackupData.fromJson(json.decode(decryptedData));
// 执行数据恢复
await _restoreFromBackup(backupData, ledgerId);
// 更新状态
final fingerprint = await _calculateLocalFingerprint(ledgerId);
_statusCache = SyncStatus.synced(
localFingerprint: fingerprint,
cloudFingerprint: fingerprint,
isUpToDate: true,
lastSyncAt: DateTime.now(),
);
return SyncResult.success(
syncedAt: DateTime.now(),
message: 'Data restored successfully',
);
} catch (e) {
logger.error('Failed to download restore', e);
return SyncResult.failure(error: e.toString());
}
}
// 数据加密/解密
Future<Uint8List> _encryptBackupData(String jsonData) async {
final key = await _getDerivedKey();
final cipher = AESCipher(key);
return cipher.encrypt(utf8.encode(jsonData));
}
Future<String> _decryptBackupData(Uint8List encryptedData) async {
final key = await _getDerivedKey();
final cipher = AESCipher(key);
final decrypted = cipher.decrypt(encryptedData);
return utf8.decode(decrypted);
}
}数据安全保障
端到端加密
class AESCipher {
final Uint8List key;
AESCipher(this.key);
Uint8List encrypt(List<int> plaintext) {
final cipher = AESEngine()
..init(true, KeyParameter(key));
// 生成随机IV
final iv = _generateRandomIV();
final cbcCipher = CBCBlockCipher(cipher)
..init(true, ParametersWithIV(KeyParameter(key), iv));
// PKCS7填充
final paddedPlaintext = _padPKCS7(Uint8List.fromList(plaintext));
final ciphertext = Uint8List(paddedPlaintext.length);
for (int i = 0; i < paddedPlaintext.length; i += 16) {
cbcCipher.processBlock(paddedPlaintext, i, ciphertext, i);
}
// IV + 密文
return Uint8List.fromList([...iv, ...ciphertext]);
}
Uint8List decrypt(Uint8List encrypted) {
// 分离IV和密文
final iv = encrypted.sublist(0, 16);
final ciphertext = encrypted.sublist(16);
final cipher = AESEngine()
..init(false, KeyParameter(key));
final cbcCipher = CBCBlockCipher(cipher)
..init(false, ParametersWithIV(KeyParameter(key), iv));
final decrypted = Uint8List(ciphertext.length);
for (int i = 0; i < ciphertext.length; i += 16) {
cbcCipher.processBlock(ciphertext, i, decrypted, i);
}
// 移除PKCS7填充
return _removePKCS7Padding(decrypted);
}
Uint8List _generateRandomIV() {
final random = Random.secure();
return Uint8List.fromList(
List.generate(16, (_) => random.nextInt(256))
);
}
}密钥派生
Future<Uint8List> _getDerivedKey() async {
final user = await auth.getCurrentUser();
if (user == null) throw Exception('User not authenticated');
// 使用用户ID和设备特征生成密钥
final salt = utf8.encode('${user.id}_${await _getDeviceId()}');
final password = utf8.encode(user.id);
// PBKDF2密钥派生
final pbkdf2 = PBKDF2KeyDerivator(HMac(SHA256Digest(), 64))
..init(Pbkdf2Parameters(salt, 10000, 32));
return pbkdf2.process(password);
}
Future<String> _getDeviceId() async {
final prefs = await SharedPreferences.getInstance();
String? deviceId = prefs.getString('device_id');
if (deviceId == null) {
deviceId = const Uuid().v4();
await prefs.setString('device_id', deviceId);
}
return deviceId;
}冲突处理策略
冲突检测
class ConflictDetector {
static ConflictResolution detectConflict({
required BackupData localData,
required BackupData cloudData,
required DateTime lastSyncAt,
}) {
final localChanges = <String, dynamic>{};
final cloudChanges = <String, dynamic>{};
// 检测交易记录冲突
_detectTransactionConflicts(
localData.transactions,
cloudData.transactions,
lastSyncAt,
localChanges,
cloudChanges,
);
if (localChanges.isEmpty && cloudChanges.isEmpty) {
return ConflictResolution.noConflict();
}
if (localChanges.isNotEmpty && cloudChanges.isEmpty) {
return ConflictResolution.localWins(changes: localChanges);
}
if (localChanges.isEmpty && cloudChanges.isNotEmpty) {
return ConflictResolution.cloudWins(changes: cloudChanges);
}
// 存在双向冲突，需要用户选择
return ConflictResolution.needsResolution(
localChanges: localChanges,
cloudChanges: cloudChanges,
);
}
static void _detectTransactionConflicts(
Map<String, dynamic> localTxs,
Map<String, dynamic> cloudTxs,
DateTime lastSyncAt,
Map<String, dynamic> localChanges,
Map<String, dynamic> cloudChanges,
) {
// 检测本地新增/修改的交易
localTxs.forEach((id, localTx) {
final txUpdatedAt = DateTime.parse(localTx['updatedAt'] ?? localTx['createdAt']);
if (txUpdatedAt.isAfter(lastSyncAt)) {
localChanges = localTx;
}
});
// 检测云端新增/修改的交易
cloudTxs.forEach((id, cloudTx) {
final txUpdatedAt = DateTime.parse(cloudTx['updatedAt'] ?? cloudTx['createdAt']);
if (txUpdatedAt.isAfter(lastSyncAt)) {
cloudChanges = cloudTx;
}
});
}
}冲突解决
class ConflictResolver {
static Future<BackupData> resolveConflict({
required BackupData localData,
required BackupData cloudData,
required ConflictResolution resolution,
}) async {
switch (resolution.type) {
case ConflictType.noConflict:
return localData;
case ConflictType.localWins:
return localData;
case ConflictType.cloudWins:
return cloudData;
case ConflictType.needsResolution:
return await _mergeData(localData, cloudData, resolution);
}
}
static Future<BackupData> _mergeData(
BackupData localData,
BackupData cloudData,
ConflictResolution resolution,
) async {
// 实现智能合并策略
final mergedTransactions = <String, dynamic>{};
// 优先保留较新的数据
mergedTransactions.addAll(cloudData.transactions);
resolution.localChanges.forEach((id, localTx) {
final localUpdatedAt = DateTime.parse(localTx['updatedAt'] ?? localTx['createdAt']);
if (resolution.cloudChanges.containsKey(id)) {
final cloudTx = resolution.cloudChanges;
final cloudUpdatedAt = DateTime.parse(cloudTx['updatedAt'] ?? cloudTx['createdAt']);
// 保留时间戳较新的版本
if (localUpdatedAt.isAfter(cloudUpdatedAt)) {
mergedTransactions = localTx;
} else {
mergedTransactions = cloudTx;
}
} else {
mergedTransactions = localTx;
}
});
return BackupData(
version: localData.version,
createdAt: DateTime.now(),
deviceId: localData.deviceId,
ledgers: localData.ledgers,
accounts: localData.accounts,
categories: localData.categories,
transactions: mergedTransactions,
);
}
}性能优化
增量同步优化
class IncrementalSync {
static Future<BackupData> generateIncrementalBackup({
required int ledgerId,
required DateTime lastSyncAt,
required BeeRepository repo,
}) async {
// 只获取自上次同步后的变更数据
final changedTransactions = await repo.getTransactionsSince(
ledgerId: ledgerId,
since: lastSyncAt,
);
final changedAccounts = await repo.getAccountsSince(
ledgerId: ledgerId,
since: lastSyncAt,
);
// 构建增量备份数据
return BackupData(
version: '1.0',
createdAt: DateTime.now(),
deviceId: await _getDeviceId(),
ledgers: {}, // 账本信息变化较少，可按需包含
accounts: _mapAccountsToJson(changedAccounts),
categories: {}, // 分类变化较少，可按需包含
transactions: _mapTransactionsToJson(changedTransactions),
);
}
static Map<String, dynamic> _mapTransactionsToJson(List<Transaction> transactions) {
return Map.fromEntries(
transactions.map((tx) => MapEntry(
tx.id.toString(),
{
'id': tx.id,
'ledgerId': tx.ledgerId,
'type': tx.type,
'amount': tx.amount,
'categoryId': tx.categoryId,
'accountId': tx.accountId,
'toAccountId': tx.toAccountId,
'happenedAt': tx.happenedAt.toIso8601String(),
'note': tx.note,
'updatedAt': DateTime.now().toIso8601String(),
}
))
);
}
}网络优化
class NetworkOptimizer {
static const int maxRetries = 3;
static const Duration retryDelay = Duration(seconds: 2);
static Future<T> withRetry<T>(Future<T> Function() operation) async {
int attempts = 0;
while (attempts < maxRetries) {
try {
return await operation();
} catch (e) {
attempts++;
if (attempts >= maxRetries) {
rethrow;
}
// 指数退避
await Future.delayed(retryDelay * (1 << attempts));
}
}
throw Exception('Max retries exceeded');
}
static Future<bool> isNetworkAvailable() async {
try {
final result = await InternetAddress.lookup('supabase.co');
return result.isNotEmpty && result.rawAddress.isNotEmpty;
} catch (_) {
return false;
}
}
}同步操作界面
class SyncStatusWidget extends ConsumerWidget {
final int ledgerId;
const SyncStatusWidget({Key? key, required this.ledgerId}) : super(key: key);
@override
Widget build(BuildContext context, WidgetRef ref) {
final syncStatus = ref.watch(syncStatusProvider(ledgerId));
return syncStatus.when(
data: (status) => _buildStatusIndicator(status),
loading: () => const SyncLoadingIndicator(),
error: (error, _) => SyncErrorIndicator(error: error.toString()),
);
}
Widget _buildStatusIndicator(SyncStatus status) {
switch (status.type) {
case SyncStatusType.synced:
return Row(
mainAxisSize: MainAxisSize.min,
children: [
Icon(Icons.cloud_done, color: Colors.green, size: 16),
SizedBox(width: 4),
Text('已同步', style: TextStyle(fontSize: 12, color: Colors.green)),
],
);
case SyncStatusType.localOnly:
return Row(
mainAxisSize: MainAxisSize.min,
children: [
Icon(Icons.cloud_off, color: Colors.orange, size: 16),
SizedBox(width: 4),
Text('仅本地', style: TextStyle(fontSize: 12, color: Colors.orange)),
],
);
case SyncStatusType.needsUpload:
return Row(
mainAxisSize: MainAxisSize.min,
children: [
Icon(Icons.cloud_upload, color: Colors.blue, size: 16),
SizedBox(width: 4),
Text('待上传', style: TextStyle(fontSize: 12, color: Colors.blue)),
],
);
case SyncStatusType.needsDownload:
return Row(
mainAxisSize: MainAxisSize.min,
children: [
Icon(Icons.cloud_download, color: Colors.purple, size: 16),
SizedBox(width: 4),
Text('有更新', style: TextStyle(fontSize: 12, color: Colors.purple)),
],
);
default:
return SizedBox.shrink();
}
}
}最佳实践总结
1. 架构设计原则
[*]本地优先：确保应用离线可用
[*]渐进式同步：支持部分同步，不影响核心功能
[*]状态透明：让用户清楚了解同步状态
2. 安全性考虑
[*]端到端加密：敏感数据客户端加密
[*]密钥管理：使用安全的密钥派生和存储
[*]权限控制：确保用户只能访问自己的数据
3. 性能优化
[*]增量同步：只传输变更数据
[*]压缩上传：减少网络传输量
[*]后台同步：不影响用户操作
4. 用户体验
[*]状态可见：清晰的同步状态指示
[*]操作简单：一键同步，自动处理
[*]错误友好：明确的错误提示和恢复建议
实际应用效果
在BeeCount项目中，Supabase云同步系统带来了显著的价值：
[*]用户满意度提升：多设备无缝切换，用户数据永不丢失
[*]技术债务减少：基于成熟的BaaS服务，减少自建后台成本
[*]安全性保障：端到端加密确保财务数据安全
[*]开发效率：快速集成，专注业务逻辑开发
结语
Supabase作为开源的BaaS解决方案，为Flutter应用提供了完整的后端服务能力。通过合理的架构设计、安全的加密策略和良好的用户体验设计，我们可以构建出既安全又好用的云同步功能。
BeeCount的实践证明，选择合适的技术栈和设计模式，能够在保证数据安全的前提下，为用户提供便捷的多设备同步体验。这对于任何需要数据同步的应用都具有重要的参考价值。
关于BeeCount项目
项目特色
<ul>
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