前言

报错信息：

Access to XMLHttpRequest at 'http://localhost:20001/toLogin' from origin 'http://localhost:8081' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource.

前端请求成功，后端返回200，然后前端到返回拦截器response前，报错了。

解决办法

参考文档1：https://segmentfault.com/q/1010000015817945
参考文档2：https://blog.csdn.net/qq_32625839/article/details/81001125
在过滤器里面加了response配置，且添加了cors跨域配置。但是依然报错。
解决方法：
https://www.jianshu.com/p/27a1072d831c


成功

代码

import org.springframework.core.Ordered;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;
import org.springframework.web.cors.CorsConfiguration;
import org.springframework.web.cors.UrlBasedCorsConfigurationSource;
import org.springframework.web.filter.CorsFilter;

import java.util.Arrays;
import java.util.List;

/**
 * @author ：qilong sun
 * @date ：Created in 2019/12/12 16:44
 * @description：
 * @modified By：
 * @version: V1.0$
 */

@Component
@Order(Ordered.HIGHEST_PRECEDENCE)
public class AjaxCorsFilter extends CorsFilter {
    public AjaxCorsFilter() {
        super(configurationSource());
    }

    private static UrlBasedCorsConfigurationSource configurationSource() {
        CorsConfiguration corsConfig = new CorsConfiguration();
        List<String> allowedHeaders = Arrays.asList("x-auth-token", "content-type", "X-Requested-With", "XMLHttpRequest");
        List<String> exposedHeaders = Arrays.asList("x-auth-token", "content-type", "X-Requested-With", "XMLHttpRequest");
        List<String> allowedMethods = Arrays.asList("POST", "GET", "DELETE", "PUT", "OPTIONS");
        List<String> allowedOrigins = Arrays.asList("*");
        corsConfig.setAllowedHeaders(allowedHeaders);
        corsConfig.setAllowedMethods(allowedMethods);
        corsConfig.setAllowedOrigins(allowedOrigins);
        corsConfig.setExposedHeaders(exposedHeaders);
        corsConfig.setMaxAge(36000L);
        corsConfig.setAllowCredentials(true);

        UrlBasedCorsConfigurationSource source = new UrlBasedCorsConfigurationSource();
        source.registerCorsConfiguration("/**", corsConfig);
        return source;
    }
}