Spring Cloud Gateway代理WebSocket因大小写敏感Header连接失败如何解决

问题根因为Spring Cloud Gateway底层Netty默认将HTTP请求头转为小写，不符合第三方WebSocket服务对Upgrade、Connection头名称的大小写严格校验要求，可通过以下步骤修复：

步骤1：修改application.yml配置 #

在原有配置的spring.cloud.gateway.httpclient节点下新增头大小写敏感与校验关闭配置，修改后对应配置段如下：

spring:
  cloud:
    gateway:
      httpclient:
        pool:
          max-idle-time: 10s
        # 新增以下配置
        headers:
          case-sensitive: true
        validate-headers: false

步骤2：添加自定义请求头重写过滤器 #

新增全局过滤器，识别WebSocket握手请求后替换小写头为大写标准格式：

import org.springframework.cloud.gateway.filter.GatewayFilterChain;
import org.springframework.cloud.gateway.filter.GlobalFilter;
import org.springframework.core.Ordered;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.stereotype.Component;
import org.springframework.web.server.ServerWebExchange;
import reactor.core.publisher.Mono;

@Component
public class WebSocketHeaderCaseFixFilter implements GlobalFilter, Ordered {

    @Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        ServerHttpRequest request = exchange.getRequest();
        // 仅处理WebSocket握手请求
        if (!"websocket".equalsIgnoreCase(request.getHeaders().getUpgrade())) {
            return chain.filter(exchange);
        }
        ServerHttpRequest modifiedRequest = request.mutate()
                .headers(httpHeaders -> {
                    // 移除原有小写头
                    httpHeaders.remove("upgrade");
                    httpHeaders.remove("connection");
                })
                // 新增大写格式要求的头
                .header("Upgrade", "websocket")
                .header("Connection", "Upgrade")
                .build();
        return chain.filter(exchange.mutate().request(modifiedRequest).build());
    }

    @Override
    public int getOrder() {
        // 优先级高于内置WebSocket转发过滤器
        return -1;
    }
}

可选兼容配置（低版本SCG适用） #

如果上述配置不生效，可新增HttpClient自定义配置Bean强制开启大小写敏感：

import org.springframework.cloud.gateway.config.HttpClientCustomizer;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import reactor.netty.http.client.HttpClient;

@Configuration
public class HttpClientCustomConfig {
    @Bean
    public HttpClientCustomizer headerCaseCustomizer() {
        return httpClient -> httpClient
                .headers(headers -> headers.caseSensitive(true))
                .validateHeaders(false);
    }
}

配置完成后重启服务即可正常握手连接第三方WebSocket服务。

内容的提问来源于stack exchange，提问作者Jerry