如何在 Dart 服务器中为 request.response 设置 content-type？

Question

我设置我的飞镖服务器如下所示。我可以从 Flutter Mobile 应用程序发送数据并从 Dart 服务器接收数据。

如果在 dart 服务器中请求方法是 GET 我连接到 tcp 套接字获取一些数据。我需要发送到 Flutter 应用程序的数据必须采用 JSON 格式。

我尝试将 request.response.headers.contentType 设置为 json，但我不断收到一条错误消息，提示 HttpException: HTTP headers 不可变。

代码部分：

var _secureResponse = {};
_secureResponse[“Data”] = "$_returningServerData";
_secureResult = json.encode(_secureResponse);

request.response.headers.contentType = new ContentType("application", "json", charset: "utf-8");
request.response.write(_secureResult);
request.response.close();

错误：

无
未处理的异常：HttpException：HTTP headers 不可变
HttpHeaders._checkMutable (飞镖:_http/http_headers.dart:447:20)
HttpHeaders.contentType= (飞镖:_http/http_headers.dart:267:5)

服务器代码：

Future main() async {
  final HttpServer server = await HttpServer.bind("127.0.0.1", 8080);
  server.listen((HttpRequest request) async {

    print(request.headers.contentType);

    try {
      if (request.method == "GET") {
         String _requestData = ......
          Socket _socket = await Socket.connect('192.168.22.129', 3000);

          // READ FROM CSERVER
          _socket.listen((List<int> event) {
            _reply = new String.fromCharCodes(event).trim();
          });

          // WRITE TO SERVER
          _socket.add(utf8.encode('$_requestData\r\n'));

          // wait 1 seconds
          await Future.delayed(Duration(milliseconds: 1000));
          _socket.close();

          var _secureResponse = {};
          _secureResponse["Data"] = "$_reply";
          _secureResult = json.encode(_secureResponse);

          request.response.headers.contentType = new    
          ContentType("application", "json", charset: "utf-8");
          request.response.write(_secureResult);
          request.response.close();

        }

    } finally {
      var _secureResponse = {};
      _secureResponse["Data"] = "ERROR";
      _secureResult = json.encode(_secureResponse);

      request.response.headers.contentType = new 
      ContentType("application", "json", charset: "utf-8");
      request.response.write(_secureResult);
      request.response.close();
    }
  });
}

Answer 1

见https://api.dartlang.org/stable/2.1.0/dart-io/HttpHeaders-class.html

你有没有试过

request.headers.set(HttpHeaders.cacheControlHeader,
                    'max-age=3600, must-revalidate');

如果您在 Dart 中构建服务器，我可以建议您使用 package:shelf – 它对用户更友好。

如何在 Dart 服务器中为 request.response 设置 content-type？

How to set content-type for request.response in Dart Server?

json

content-type

dart

serve