AFHTTPRequestOperationManager *manager = [AFHTTPRequestOperationManager manager];
    manager.requestSerializer = [AFJSONRequestSerializer serializer];
    manager.responseSerializer = [AFJSONResponseSerializer serializer];
    [manager.requestSerializer setValue:@"application/json" forHTTPHeaderField:@"Accept"];
    [manager.requestSerializer setValue:@"application/json; charset=utf-8" forHTTPHeaderField:@"Content-Type"];