AngularJS：拒绝设置不安全标头“Access-Control-Request-Headers”

我正在尝试使用 AngularJS 调用本地运行的 REST API。这是 AngularJS 代码：

$http.defaults.headers.common = {"Access-Control-Request-Headers": "accept, origin, authorization"};

$http.defaults.headers.common['Authorization'] = 'Basic amF5M2RlYzpqYXk=';
$http({method: 'GET', url: 'http://127.0.0.1:5000/user/jay3dec'}).
        success(function(data, status, headers, config) {

        }).
        error(function(data, status, headers, config) {
            alert(data);

        });

但我在浏览器控制台中收到错误：

Refused to set unsafe header "Access-Control-Request-Headers" 

我尝试查询调用运行于的 REST APIhttp://127.0.0.1:5000/user/jay3dec http://127.0.0.1:5000/user/jay3dec使用卷曲。

curl -H "Origin: http://127.0.0.1:8000" -H "Authorization: Basic amF5M2RlYzpqYXk=" http://127.0.0.1:5000/user/jay3dec --verbose

它给出了以下输出：

> GET /user/jay3dec HTTP/1.1
> User-Agent: curl/7.35.0
> Host: 127.0.0.1:5000
> Accept: */*
> Origin: http://127.0.0.1:8000
> Authorization: Basic amF5M2RlYzpqYXk=
> 
* HTTP 1.0, assume close after body
< HTTP/1.0 200 OK
< Content-Type: application/json
< Content-Length: 454
< ETag: bff7b7db33baedb612276861e84faa8f7988efb1
< Last-Modified: Tue, 30 Dec 2014 14:32:31 GMT
< Access-Control-Allow-Origin: *
< Access-Control-Allow-Headers: Authorization
< Access-Control-Allow-Methods: HEAD, OPTIONS, GET
< Access-Control-Allow-Max-Age: 21600
< Server: Eve/0.4 Werkzeug/0.9.6 Python/2.7.6
< Date: Sun, 25 Jan 2015 20:00:29 GMT
< 
* Closing connection 0
{"username": "jay3dec", "_updated": "Tue, 30 Dec 2014 14:32:31 GMT", "password": "jay", "firstname": "jay", "lastname": "raj", "phone": "9895590754", "_links": {"self": {"href": "/user/54a2b77f691d721ee170579d", "title": "User"}, "parent": {"href": "", "title": "home"}, "collection": {"href": "/user", "title": "user"}}, "_created": "Tue, 30 Dec 2014 14:32:31 GMT", "_id": "54a2b77f691d721ee170579d", "_etag": "bff7b7db33baedb612276861e84faa8f7988efb1"}

任何人都可以发现可能是什么问题吗？

后面的代码$http.defaults.headers.common is

var xhr = createXhr();

xhr.open(method, url, true);
  forEach(headers, function(value, key) {
    if (isDefined(value)) {
        xhr.setRequestHeader(key, value);
    }
  });

...

function createXhr() {
    return new window.XMLHttpRequest();
}

参考XMLHttpRequest 规范 https://dvcs.w3.org/hg/xhr/raw-file/tip/Overview.html#dom-xmlhttprequest-setrequestheader，如果标头与以下标头之一不区分大小写匹配，浏览器将终止

Accept-Charset
Accept-Encoding
Access-Control-Request-Headers
Access-Control-Request-Method
Connection
Content-Length
...

这就是为什么你不能使用$http.defaults.headers.common to set Access-Control-Request-Headers标头。浏览器将为您处理请求标头。