项目场景：

Web前端开发经常会遇到跨域访问，如果没有办法让后台开放访问域，调用接口就会被浏览器拦截。解决跨域问题的方案，可以搭建一个后台服务做中间转发，也可以用nginxhttps://so.csdn.net/so/search?q=nginx转发。

问题描述

问题发生在nginx反向代理https://so.csdn.net/so/search?q=%E5%8F%8D%E5%90%91%E4%BB%A3%E7%90%86springboot后端应用时，前端请求后端时发生Cros错误，如下图所示。

原因分析：

1.Nginx作为代理服务，需要配置允许跨域

2.Springboot后台服务需要配置允许跨域请求

解决方案：

1.检查后台服务是否设置了允许跨域，设置方法如下:

@Configuration
public class WebMvcConfig implements WebMvcConfigurer {@Overridepublic void addCorsMappings(CorsRegistry registry) {registry.addMapping("/**").allowedHeaders("Content-Type","X-Requested-With","accept,Origin","Access-Control-Request-Method","Access-Control-Request-Headers","token").allowedMethods("*").allowedOrigins("*").allowCredentials(true);}/*** 支持PUT、DELETE请求*/@Beanpublic FormContentFilter httpPutFormContentFilter() {return new FormContentFilter();}}

2.检查nginx.conf配置文件是否允许跨域，在server配置内进行配置，配置方法如下:

    location /space-time/ {if ($request_method = OPTIONS ) {add_header Access-Control-Allow-Origin "*" always;add_header Access-Control-Allow-Methods "POST, GET, PUT, OPTIONS, DELETE";add_header Access-Control-Max-Age "3600";add_header Access-Control-Allow-Headers "Origin, X-Requested-With, Content-Type, Accept, Authorization";add_header Content-Length 0;add_header Content-Type text/plain;return 200;}proxy_set_header Content-Type application/json;add_header Access-Control-Allow-Origin "*" always;add_header Access-Control-Allow-Headers "Origin, X-Requested-With, Content-Type, Accept";add_header Access-Control-Allow-Methods "GET, POST, OPTIONS";proxy_pass http://localhost:8086/space-time/;proxy_set_header X-Real-IP $remote_addr;}