Nginx CORS 跨域资源共享问题

## 背景

新项目上线，前后端分离，遇到了跨域资源共享的问题，导致请求根本无法发送到后端，前端和后端貌似只能有一个来处理跨域问题，我们这边要采用nginx来解决跨域问题。

## Nginx的CORS配置

网上好像都是三两行解决问题。可是我这边试了很多次，也没用。

add_header Access-Control-Allow-Origin *;
add_header Access-Control-Allow-Headers X-Requested-With;
add_header Access-Control-Allow-Methods GET,POST,OPTIONS;

## 上最终的配置文件

server
{
  listen       80;
  server_name  api.example.com;
  index index.jsp index.htm index.html index.do login.vm;
  charset utf-8;
  location /
  {
    proxy_set_header  Host $host;
    proxy_set_header  X-Real-IP  $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_pass http://192.168.150.184:10000;
  }
  location /pm/ {
   add_header Access-Control-Allow-Origin 'http://pm.example.com';
   add_header Access-Control-Allow-Headers 'DNT,Keep-Alive,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Authorization,X-Auth-Token';
   add_header Access-Control-Allow-Methods 'GET,POST,OPTIONS';
   add_header Access-Control-Expose-Headers 'X-Auth-Token';
   proxy_set_header  Host $host;
   proxy_set_header  X-Real-IP  $remote_addr;
   proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
   proxy_pass http://192.168.150.184:10000/;
   if ($request_method = 'OPTIONS') {
     add_header Access-Control-Max-Age "3600" ;
     add_header Access-Control-Allow-Origin 'http://pm.example.com';
     add_header Access-Control-Allow-Headers 'DNT,Keep-Alive,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Authorization,X-Auth-Token';
     add_header Access-Control-Expose-Headers 'X-Auth-Token';
     return 200;
   }
 }
 access_log  /data/logs/example_com_access wwwlog;
 error_log   /data/logs/example_com_error ;
}