'XMLHttpRequest无法加载'从Dart客户端到本地Dart泊坞服务器的HTTP请求错误
我最近一直试图建立一个Dart客户端，与我的Dart泊坞服务器通信。如果我在任何浏览器上运行这个url（localhost：8080 / id / 6192449487634432），我得到一个我设置的JSON，但是，如果使用
I've lately been trying to build a Dart client that communicates with my Dart docker server. If I run this url (localhost:8080/id/6192449487634432) on any browser I get back a JSON that I've set up, however, if a use
HttpRequest
.getString ("http://localhost:8080/id/6192449487634432")
.then (print);
在Dart客户端，我得到这个奇怪的错误
on the Dart client, I get this weird error
XMLHttpRequest cannot load http://localhost:8080/id/6192449487634432. No 'Access-Control-Allow-Origin'
header is present on the requested resource. Origin 'http://localhost:8081' is therefore not allowed access.
我已经搜索，一些解决方法是构建一个PHP代理我是一个新的web开发一般来说，我绝对不知道什么是代理是或如何建立一个。有没有一个干净的解决方案，我可以使用？我有一个Redstone服务器和AngularDart客户端。
I've searched and some workarounds have been to build a PHP proxy (no thanks). I am new to web development in general and I definitely don't know what a proxy is or how to build one. Is there a clean solution I could use? I have a Redstone server and and AngularDart client.
非常感谢。
由与docker服务器不同的服务器提供。这是一个浏览器问题，不是Dart特有的。幸运的是，解决方案很容易。
This happens when your client app is served from a different server than your docker server. This is a browser issue, not specific to Dart. Luckily, the solution is easy.
请务必在每次请求时从您的服务器发送CORS头文件。最简单的解决方法是添加以下标题：
Be sure to send CORS headers from your server, on every request. The easiest way to solve this is to add the following header:
Access-Control-Allow-Origin：*
我不知道Redstone的具体细节，但务必设置标题键 Access-Control-Allow-Origin $ c GET ， HEAD 上的和值 * 和 POST 方法。是的，您需要在 HEAD 请求上设置此标头，因为有时浏览器会发出HEAD请求来检查是否启用CORS。
I don't know the specifics of Redstone, but be sure to set the header key Access-Control-Allow-Origin and value * on GET, HEAD, and POST methods. Yes, you need to set this header on HEAD requests because sometimes the browser does a HEAD request to check if CORS is enabled.
要了解有关CORS的详情，请访问 http://enable-cors.org/
Learn more about CORS at http://enable-cors.org/