java中reseponse中自定义的头部前端没法看到的（做前后端项目，springboot 跨域问题的时候）

可以在跨域的bean上加入东西：

如图

    /** 
     * 跨域过滤器 
     * @return 
     */   
    @Bean  
    public FilterRegistrationBean corsFilter() {  
        UrlBasedCorsConfigurationSource source = new UrlBasedCorsConfigurationSource();  
        CorsConfiguration config = new CorsConfiguration();  
        config.setAllowCredentials(true);  
        config.addAllowedOrigin("*");  
        config.addAllowedHeader(CorsConfiguration.ALL);  
        config.addAllowedMethod(CorsConfiguration.ALL);
        config.addExposedHeader("filename");
        source.registerCorsConfiguration("/**", config);  
        FilterRegistrationBean bean = new FilterRegistrationBean(new CorsFilter(source));  
        bean.setOrder(Ordered.HIGHEST_PRECEDENCE);  
        return bean;  
    }