请求的资源上不存在 Access-Control-Allow-Origin 标头
我想访问来自同一个域但具有不同端口号的信息，为此我添加了 Access-Control-Allow-Origin 与响应标头.
I want to access information from same domain but with different port number, To allow this I am adding Access-Control-Allow-Origin with the response header.
Servlet 代码:(出现在 www.example.com:PORT_NUMBER 上)
Servlet Code:(present on www.example.com:PORT_NUMBER)
String json = new Gson().toJson(list);
response.setContentType("application/json");
response.setCharacterEncoding("UTF-8");
response.setHeader("Access-Control-Allow-Origin", "*");//cross domain request/CORS
response.getWriter().write(json);
jQuery 代码:(出现在 www.example.com)
jQuery code:(present on www.example.com)
$.post('http://www.example.com:PORT_NUMBER/MYSERVLET',{MyParam: 'value'}).done(function(data)
{
alert(data);
});
我多次收到此错误(在控制台中):
Several times I am getting this error(in console):
XMLHttpRequest cannot load 'http://www.example.com:PORT_NUMBER/MYSERVLET'
No 'Access-Control-Allow-Origin' header is present on the requested resource.
这个错误大多是在 $.post 被执行时第一次发生.第二次允许.
This error mostly occures first time when $.post gets executed. Second time it allows.
我的问题是 servlet 或 jQuery 代码中是否缺少?
My question is that is there missing in servlet or in jQuery code?
任何建议将不胜感激.
更新1
我变了:
response.setHeader("Access-Control-Allow-Origin", "*");
收件人:
response.setHeader("Access-Control-Allow-Origin", "http://www.example.com");
然后我在控制台中收到此错误:
Then I am getting this error in console:
XMLHttpRequest cannot load http://www.example.com:PORT_NUMBER/MyServletName
The 'Access-Control-Allow-Origin' whitelists only 'http://www.example.com'
Origin 'http://www.example.com' is not in the list,
and is therefore not allowed access.
[注意:白名单和来源相同，但仍然报错.它有时有效，有时会出现上述错误.]
[Note: whitelist and origin are same, but still it gives error. It works sometimes, and gives above error sometimes.]
如果您需要更多信息，请告诉我.
Let me know if you need anymore information.
推荐答案
解决方案:
我没有使用 setHeader 方法，而是使用了 addHeader.
Solution:
Instead of using setHeader method I have used addHeader.
response.addHeader("Access-Control-Allow-Origin", "*");
* 上面一行将允许访问所有域，仅允许访问特定域:
* in above line will allow access to all domains, For allowing access to specific domain only:
response.addHeader("Access-Control-Allow-Origin", "http://www.example.com");
有关 IE<=9 的问题，请参阅 这里.
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