后端配置了代码：

spring:
  application:
    name: spzx-server-gateway
  cloud:
    nacos:
      discovery:
        server-addr: localhost:8848
    gateway:
      discovery:
        locator:
          enabled: true
      globalcors:
        cors-configurations:
          '[/**]':
            allowedOriginPatterns: "*"
            # 允许请求中携带的头信息
            allowedHeaders: "*"
            # 运行跨域的请求方式
            allowedMethods: "*"
            # 跨域检测的有效期,单位s
            maxAge: 36000

但是后端启动后，前端报错'Access-Control-Allow-Origin' CORS 多个头

是因为多重配置导致：

比如说：

package com.atguigu.spzx.product.controller;

import com.atguigu.spzx.model.entity.product.Category;
import com.atguigu.spzx.model.entity.product.ProductSku;
import com.atguigu.spzx.model.vo.common.Result;
import com.atguigu.spzx.model.vo.common.ResultCodeEnum;
import com.atguigu.spzx.model.vo.h5.IndexVo;
import com.atguigu.spzx.product.service.CategoryService;
import com.atguigu.spzx.product.service.ProductSkuService;
import io.swagger.v3.oas.annotations.Operation;
import io.swagger.v3.oas.annotations.tags.Tag;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.CrossOrigin;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

@Tag(name = "首页接口管理")
@RestController
@RequestMapping(value="/api/product/index")
@CrossOrigin   重复配置跨域
public class IndexController {
    @Autowired
    private CategoryService categoryService;

    @Autowired
    private ProductSkuService productSkuService;

    //查询所有一级分类
    //查询畅销商品
    @Operation(summary = "获取首页数据")
    @GetMapping
    public Result<IndexVo> findData(){
        //查询所有一级分类
        List<Category> categoryList=categoryService.findOneCategory();
        查询畅销商品
        List<ProductSku> productSkuList=productSkuService.findProductSkuBySale();
        IndexVo indexVo=new IndexVo();
        indexVo.setCategoryList(categoryList);
        indexVo.setProductSkuList(productSkuList);
        return Result.build(indexVo, ResultCodeEnum.SUCCESS);

    }
}

如上代码：注解重复配置跨域

再比如利用java代码配置导致前端报错'Access-Control-Allow-Origin' CORS 多个头：

package com.atguigu.spzx.manager.config;



import com.atguigu.spzx.manager.properties.UserAuthProperties;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.springframework.web.servlet.config.annotation.CorsRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
@Component
@SuppressWarnings({"all","silent"})
public class WebMvcConfiguration implements WebMvcConfigurer {
    @Autowired
    private UserAuthProperties userAuthProperties;
    @Autowired

    public void addCorsMappings(CorsRegistry registry) {
        registry.addMapping("/**")       //添加路径规则
                .allowCredentials(true)   //是否允许在跨域情况下传递cookie
                .allowedOriginPatterns("*")//允许请求来源的域规则
                .allowedMethods("*")
                .allowedHeaders("*");           //允许所有请求头
    }


}