5.28

一、增量同步实现
基于时间戳的增量数据同步：
java
// 后端增量数据接口
@RestController
@RequestMapping("/api/sync")
public class SyncController {
@Autowired
private UserService userService;

@GetMapping("/users")
public ResponseEntity<List<User>> getUpdatedUsers(@RequestParam("lastSyncTime") long lastSyncTime) {
    List<User> updatedUsers = userService.getUsersUpdatedAfter(lastSyncTime);
    return ResponseEntity.ok(updatedUsers);
}

}

// Android端同步逻辑
public class DataSyncManager {
private static final long SYNC_INTERVAL = 24 * 60 * 60 * 1000; // 24小时

public void syncData() {
    long lastSyncTime = getLastSyncTime();
    long currentTime = System.currentTimeMillis();
    
    if (currentTime - lastSyncTime >= SYNC_INTERVAL) {
        // 执行同步
        syncUsers(lastSyncTime);
        updateLastSyncTime(currentTime);
    }
}

private void syncUsers(long lastSyncTime) {
    apiService.getUpdatedUsers(lastSyncTime)
            .enqueue(new Callback<List<User>>() {
                @Override
                public void onResponse(Call<List<User>> call, Response<List<User>> response) {
                    if (response.isSuccessful() && response.body() != null) {
                        // 更新本地数据库
                        saveUsersToLocalDb(response.body());
                    }
                }
                
                @Override
                public void onFailure(Call<List<User>> call, Throwable t) {
                    // 处理同步失败
                }
            });
}

private long getLastSyncTime() {
    // 从本地获取上次同步时间
    return preferences.getLong("last_sync_time", 0);
}

private void updateLastSyncTime(long time) {
    // 更新上次同步时间
    preferences.edit().putLong("last_sync_time", time).apply();
}

}
二、冲突解决策略
实现客户端与服务器的数据冲突检测与解决：
java
// 数据版本控制实体
@Entity
public class User {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;

private String name;

@Version
private Integer version;

// getters and setters

}

// 冲突解决策略
public enum ConflictResolutionStrategy {
SERVER_WINS {
@Override
public User resolve(User client, User server) {
return server;
}
},
CLIENT_WINS {
@Override
public User resolve(User client, User server) {
return client;
}
},
MERGE {
@Override
public User resolve(User client, User server) {
// 自定义合并逻辑
User merged = new User();
merged.setId(client.getId());
merged.setName(client.getName() != null ? client.getName() : server.getName());
merged.setVersion(server.getVersion());
return merged;
}
};

public abstract User resolve(User client, User server);

}