springcloud gateway添加跨域配置：

spring.cloud.gateway.globalcors.cors-configurations.[/**].allowed-origins=*
spring.cloud.gateway.globalcors.cors-configurations.[/**].allowed-methods=*
spring.cloud.gateway.globalcors.cors-configurations.[/**].allowed-headers=*
spring.cloud.gateway.globalcors.cors-configurations.[/**].allow-credentials=true

使用其他客户端调用接口报错：

The 'Access-Control-Allow-Origin' header contains multiple values 'null, nul

发现是重复的请求头导致的报错

添加过滤器去除重复请求头：

@Component
public class CorsResponseHeaderFilter implements GlobalFilter, Ordered {
    @Override
    public int getOrder() {
        // 指定此过滤器位于NettyWriteResponseFilter之后
        // 即待处理完响应体后接着处理响应头
        return NettyWriteResponseFilter.WRITE_RESPONSE_FILTER_ORDER + 1;
    }

    @Override
    @SuppressWarnings("serial")
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        return chain.filter(exchange).then(Mono.defer(() -> {
            exchange.getResponse().getHeaders().entrySet().stream()
                    .filter(kv -> (kv.getValue() != null && kv.getValue().size() > 1))
                    .filter(kv -> (kv.getKey().equals(HttpHeaders.ACCESS_CONTROL_ALLOW_ORIGIN)
                            || kv.getKey().equals(HttpHeaders.ACCESS_CONTROL_ALLOW_CREDENTIALS)))
                    .forEach(kv ->
                    {
                        kv.setValue(new ArrayList<String>() {{add(kv.getValue().get(0));}});
                    });

            return chain.filter(exchange);
        }));
    }
}

原文：https://blog.csdn.net/xht555/article/details/89484091