摘要：
跨域问题Java方式解决及Nginx方式解决：
1，Response for preflight has invalid HTTP status code 403
2，Nginx允许跨域访问的配置问题
3，nginx: [emerg] unknown directive "if($request_method"
4，The 'Access-Control-Allow-Origin' header contains multiple values '*, *', but only one is allowed. 阅读全文