后端实现跨域配置

`package com.IO.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.cors.CorsConfiguration;
import org.springframework.web.cors.UrlBasedCorsConfigurationSource;
import org.springframework.web.filter.CorsFilter;

@Configuration
public class CorsConfig {
@Bean
public CorsFilter corsFilter(){//注入过滤器
CorsConfiguration corsConfiguration=new CorsConfiguration();
corsConfiguration.addAllowedOrigin("");
corsConfiguration.addAllowedHeader("");
corsConfiguration.addAllowedMethod("*");
UrlBasedCorsConfigurationSource source=new UrlBasedCorsConfigurationSource();
source.registerCorsConfiguration("/**",corsConfiguration);
return new CorsFilter(source);
}

}`