mongoose中http server服务器解决“Access-Control-Allow-Origin mongoose”跨域问题
问题
使用mongoose做http服务器，自己构造的浏览器端jquery在访问server时，会遇到：
Access to XMLHttpRequest at 'http://127.0.0.1:8000/' from origin 'null' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.
jquery的程序：
$.get("http://127.0.0.1:8000",function(d)
{alert(d);
});
解决：
在mongoose返回响应串中，如下构造：
使用 mg_http_reply
char str[128] = "respnose hello";
mg_http_reply(c, 200, "Access-Control-Allow-Origin: *\n""Access-Control-Allow-Methods: *\n""Access-Control-Allow-Headers: *\n", "%s\n", str);
使用mg_printf
std::string str = "respnose hello";
mg_printf(c, "HTTP/1.1 200 OK\r\n""Content-Type: text/plain\n""Cache-Control: no-cache\n""Content-Length: %d\n""Access-Control-Allow-Origin: *\n""Access-Control-Allow-Methods: *\n""Access-Control-Allow-Headers: *\n\n""%s\n", str.length(), str.c_str());
最终，返回的的串，看起来应该是这样：
