HttpRequest.setRequestHeader 在 Dart 上生成 DOM 异常 11

Question

我正在按照本教程运行从dart到我的Ruby on rails后端应用程序的POST方法。因此，在第一次尝试本教程中显示的代码时，只需更改我的 URL 和 JSON 数据即可。

void main() {   
  String jsonData = '{"color":"blue","x":"100","y":"100"}'; 
  saveData(jsonData, onSuccess); // send the data to  // the server
}
void onSuccess(HttpRequest req) {
    print(req.responseText); // print the received raw JSON text
}
void saveData(String data, onSuccess(HttpRequest req)) {
  HttpRequest req = new HttpRequest(); // create a new XHR
  // add an event handler that is called when the request finishes
  req.on.readyStateChange.add((Event e) {
    if (req.readyState == HttpRequest.DONE &&
        (req.status == 200 || req.status == 0)) {
      onSuccess(req); // called when the POST successfully completes
    }
  });
  var url = "http://localhost:3030/colored_rectangles.json";
  req.open("POST", url); // Use POST http method to send data in the next call
  req.send(data); // kick off the request to the server
}

这是我的控制器中的方法和 ruby 中的模型（非常简单，用脚手架生成）：

  # POST /colored_rectangles
  # POST /colored_rectangles.json
  def create
    @colored_rectangle = ColoredRectangle.new(params[:colored_rectangle])
    respond_to do |format|
      if @colored_rectangle.save
        format.html { redirect_to @colored_rectangle, notice: 'Colored rectangle was successfully created.' }
        format.json { render json: @colored_rectangle, status: :created, location: @colored_rectangle }
      else
        format.html { render action: "new" }
        format.json { render json: @colored_rectangle.errors, status: :unprocessable_entity }
      end
    end
  end

class ColoredRectangle < ActiveRecord::Base
  attr_accessible :color, :x, :y
end

当我运行代码时，我在 Dart 中收到以下错误：

 Failed to load resource: the server responded with a status of 500 (Internal Server Error)
  http://localhost:3030/colored_rectangles.json

和 Rails 中的登录：

REXML::ParseException (The document "{"color":"blue","x":"100","y":"100"}" does not have a valid root):
 activesupport (3.2.9) lib/active_support/xml_mini/rexml.rb:35:in `parse'
 C:in `parse'
  etc....

阅读此问题后，我尝试将标头更改为"内容类型：应用程序/json"，然后我尝试调用过度的MimeType方法，但它给了我相同的错误。

req.overrideMimeType("application/json");

我还调用了setRequestHeader方法，代码如下：

void saveLanguageData(String data, onSuccess(HttpRequest req)) {
  HttpRequest req = new HttpRequest(); // create a new XHR
  // add an event handler that is called when the request finishes
  req.on.readyStateChange.add((Event e) {
    if (req.readyState == HttpRequest.DONE &&
        (req.status == 200 || req.status == 0)) {
      onSuccess(req); // called when the POST successfully completes
    }
  });
  var url = "http://localhost:3030/colored_rectangles.json";
  req.setRequestHeader("Content-type", "application/json"); //This was added
  req.open("POST", url); // Use POST http method to send data in the next call
  req.send(data); // kick off the request to the server
}

但是我从Dart收到以下错误：

Exception: Error: INVALID_STATE_ERR: DOM Exception 11
Stack Trace: #0      HttpRequest.setRequestHeader (E:bbuildslavedartium-win-full-trunkbuildsrcbuildReleaseobjglobal_intermediatewebkitbindingsdartdarthtmlHttpRequest.dart:34:1)
#1      saveLanguageData (http://localhost:3030/rademo_dart/web/rademo.dart:45:23)
#2      main (http://localhost:3030/rademo_dart/web/rademo.dart:10:19)

任何帮助，不胜感激。提前谢谢。

Answer 1

哦，好吧，我找到了问题的答案...实际上 setRequestHeader 需要在 req.open 之后调用，因此 saveData 方法代码如下：

void saveData(String data, onSuccess(HttpRequest req)) {
  HttpRequest req = new HttpRequest(); // create a new XHR
  // add an event handler that is called when the request finishes
  req.on.readyStateChange.add((Event e) {
    if (req.readyState == HttpRequest.DONE &&
        (req.status == 200 || req.status == 0)) {
      onSuccess(req); // called when the POST successfully completes
    }
  });
  var url = "http://localhost:3030/colored_rectangles.json";
  req.open("POST", url); // Use POST http method to send data in the next call
  req.setRequestHeader("Content-type", "application/json");
  req.send(data); // kick off the request to the server
}

Answer 2

在@colored_rectangle = ColoredRectangle.new(params[:colored_rectangle]) 上，在 create 方法中，您将数据发送到 ColoredRectangle 的构造函数，但您使用的是根:colored_rectangle。此根不存在于您发送的 json 中。要修复它，只需将根添加到 json，如下所示：String jsonData = '{"colored_rectangle": {"color":"blue","x":"100","y":"100"}}';