实现GlobalFilter, Ordered接口即可，详见注释

记得加@Component注解

模板如下

@Component
@Slf4j
public class GatewayFilter implements GlobalFilter, Ordered {
    @Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain)
    {
        System.out.println("time:"+new Date()+"\t 自定义的全局过滤器："+"GatewayFilter");

        // 提取出参数key为username的值
        String uname = exchange.getRequest().getQueryParams().getFirst("username");
        
        // 拦截
        if (username == null) {
            System.out.println("****用户名为null，无法登录");
            exchange.getResponse().setStatusCode(HttpStatus.NOT_ACCEPTABLE); // set一个不接受的代码
            return exchange.getResponse().setComplete();
        }
        
        // 放行
        return chain.filter(exchange);
    }

    @Override
    public int getOrder() {
        return 0;
    }
}

如果请求不加username参数，就会被拦截