springboot2.4.0 集成 gateway 解决 跨域问题

问题：
Springboot升级至2.4.0中出现的跨域问题。
分析：
Springboot2.3.5.RELEASE时，我们可以使用CorsWebFilter进行如下设置解决跨域问题。

public CorsWebFiltercorsWebFilter(){
        UrlBasedCorsConfigurationSource configurationSource=newUrlBasedCorsConfigurationSource(newPathPatternParser());
        CorsConfiguration configuration=newCorsConfiguration();//       配置跨域
        configuration.setAllowCredentials(true);
        configuration.addAllowedOrigin("*");
        configuration.addAllowedHeader("*");
        configuration.addAllowedMethod("*");

        configurationSource.registerCorsConfiguration("/**", configuration);returnnewCorsWebFilter(configurationSource);}

但是在spring boot 2.4.0 版本以后，配置完成后，我们去页面请求数据，就会发现：

暴漏的问题居然还是跨域问题，然后查看后台控制台，出现了如下的异常：

2020-12-1020:55:18.274 ERROR7576---[ctor-http-nio-5] a.w.r.e.AbstractErrorWebExceptionHandler:[28bc5558-2]500 Server Errorfor HTTP OPTIONS"/api/login"

java.lang.IllegalArgumentException: When allowCredentials istrue, 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.
	at org.springframework.web.cors.CorsConfiguration.validateAllowCredentials(CorsConfiguration.java:457)~[spring-web-5.3.1.jar:5.3.1]
	Suppressed: reactor.core.publisher.FluxOnAssembly$OnAssemblyException: 
Error has been observed at the followingsite(s):|_ checkpoint ⇢ org.springframework.cloud.gateway.filter.WeightCalculatorWebFilter[DefaultWebFilterChain]

提示很明显：

When allowCredentials istrue, 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.

意思就是不能在configuration.setAllowCredentials(true)的时候对addAllowedOrigin设置为"*"，而要使用allowedOriginPatterns这个字段来设置origin。

对于spring boot 2.4.0出现的跨域异常问题，直接给出解决方案。

import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import org.springframework.web.cors.CorsConfiguration;import org.springframework.web.cors.reactive.CorsWebFilter;import org.springframework.web.cors.reactive.UrlBasedCorsConfigurationSource;import org.springframework.web.util.pattern.PathPatternParser;import java.util.ArrayList;import java.util.List;/**
 * @Author: 冬生草
 * @Date: 2020/12/10 21:11
 * @Description: 跨域问题
 */@ConfigurationpublicclassCorsConfig{@Beanpublic CorsWebFiltercorsWebFilter(){
        UrlBasedCorsConfigurationSource configurationSource=newUrlBasedCorsConfigurationSource(newPathPatternParser());
        CorsConfiguration configuration=newCorsConfiguration();//       配置跨域
        configuration.setAllowCredentials(true);
        List<String> allowedOriginPatterns=newArrayList<>();
        allowedOriginPatterns.add(CorsConfiguration.ALL);
        configuration.setAllowedOriginPatterns(allowedOriginPatterns);

        configuration.addAllowedHeader(CorsConfiguration.ALL);
        configuration.addAllowedMethod(CorsConfiguration.ALL);

        configurationSource.registerCorsConfiguration("/**", configuration);returnnewCorsWebFilter(configurationSource);}}

使用configuration.setAllowedOriginPatterns(allowedOriginPatterns) 就可以解决问题。
那么，CorsConfiguration.ALL 这是个什么东西呢？在源码中是这么写的。

如果是自定义origin的话，只需要将自定义的origin以字符串的形式放入到list集合中即可。
修改完毕后测试结果如下：