若依：设置跨域配置位置和图片中框出代码

@Configuration
public class WebMvcConfig implements WebMvcConfigurer {
 
    /**
     * 开启跨域
     */
    @Override
    public void addCorsMappings(CorsRegistry registry) {
        // 设置允许跨域的路由
        registry.addMapping("/**")
                // 设置允许跨域请求的域名
                .allowedOriginPatterns("*")
                // 是否允许证书（cookies）
                .allowCredentials(true)
                // 设置允许的方法
                .allowedMethods("*")
                // 跨域允许时间
                .maxAge(3600);
    }
 
}

强调：除了以上代码，还要确认访问路径为 anon

ResourcesConfig.java

package com.ruoyi.framework.config;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.*;
import com.ruoyi.common.config.RuoYiConfig;
import com.ruoyi.common.constant.Constants;
import com.ruoyi.framework.interceptor.RepeatSubmitInterceptor;

/**
 * 通用配置
 *
 * @author ruoyi
 */
@Configuration
public class ResourcesConfig implements WebMvcConfigurer {
    /**
     * 首页地址
     */
    @Value("${shiro.user.indexUrl}")
    private String indexUrl;

    @Autowired
    private RepeatSubmitInterceptor repeatSubmitInterceptor;

    /**
     * 默认首页的设置，当输入域名是可以自动跳转到默认指定的网页
     */
    @Override
    public void addViewControllers(ViewControllerRegistry registry) {
        registry.addViewController("/").setViewName("forward:" + indexUrl);
    }

    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
        /** 本地文件上传路径 */
        registry.addResourceHandler(Constants.RESOURCE_PREFIX + "/**").addResourceLocations("file:" + RuoYiConfig.getProfile() + "/");

        /** swagger配置 */
        registry.addResourceHandler("swagger-ui.html").addResourceLocations("classpath:/META-INF/resources/");
        registry.addResourceHandler("/webjars/**").addResourceLocations("classpath:/META-INF/resources/webjars/");
    }

    /**
     * 自定义拦截规则
     */
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(repeatSubmitInterceptor).addPathPatterns("/**");

    }

    /**
     * zhangxuDev 配置跨域问题
     * @param registry
     */
    @Override
    public void addCorsMappings(CorsRegistry registry) {
        // 设置允许跨域的路径
        registry.addMapping("/api/**")
                // 设置允许跨域请求的域名
                .allowedOrigins("*")
                // 是否允许证书
                .allowCredentials(true)
                // 设置允许的方法
                .allowedMethods("GET", "POST", "DELETE", "PUT")
                // 设置允许的header属性
                .allowedHeaders("*")
                // 跨域允许时间
                .maxAge(3600);
    }

}

扩散提示：

SpringBoot升级2.4.0所出现的问题：When allowCredentials is true, allowedOrigins cannot contain the specia

When allowCredentials is true, allowedOrigins cannot contain the special value "*“since that cannot be set on the “Access-Control-Allow-Origin” response header. To allow credentials to a set of origins, list them explicitly or consider using"allowedOriginPatterns” instead.
翻译如下：

解决办法：跨域配置报错，将.allowedOrigins替换成.allowedOriginPatterns即可。

修改前：

@Configuration
public class WebMvcConfig implements WebMvcConfigurer {
 
    /**
     * 开启跨域
     */
    @Override
    public void addCorsMappings(CorsRegistry registry) {
        // 设置允许跨域的路由
        registry.addMapping("/**")
                // 设置允许跨域请求的域名
                .allowedOrigins("*")
                // 是否允许证书（cookies）
                .allowCredentials(true)
                // 设置允许的方法
                .allowedMethods("*")
                // 跨域允许时间
                .maxAge(3600);
    }
 
}