WebClient添加自定义Header后抛出连接提前关闭异常求助

问题 #

以下是我编写的代码：

ObjectMapper mapper = new ObjectMapper();
Consumer<HttpHeaders> headersConsumer = headers -> headers.addAll(httpHeaders);
var map = mapper.readValue(payload, Map.class);
var ref = new AtomicReference<ClientResponse>();
var responseMono = webClient
                  .post()
                  .uri(uri)
                  .headers(headersConsumer)
                  .body(Mono.just(map), Map.class)
                  .exchangeToMono(response -> {
                     ref.set(response);
                     if (response.statusCode().equals(HttpStatus.OK)) {
                        return response.bodyToMono(String.class);
                     }
                     else {
                        return response.createException().flatMap(Mono::error);
                     }
             });
var body = responseMono.block();

移除headersConsumer时代码正常运行，但传入该消费者后抛出异常：

WebClientRequestException: Connection prematurely closed BEFORE response; nested exception is reactor.netty.http.client.PrematureCloseException

传入的请求头如下：

{content-length=540, postman-token=ab567ea9-9025-413a-bd4b-87552a6c48b2, host=localhost:8080, content-type=application/json, connection=keep-alive, accept-encoding=gzip, deflate, br, user-agent=PostmanRuntime/7.29.0, accept=*/*}

请求排查异常原因并提供解决方案。

原因分析 #

• Content-Length不匹配：手动传入的content-length=540和WebClient实际发送的请求体长度不一致，服务器校验失败后直接关闭连接，触发异常。WebClient会自动计算并设置正确的Content-Length或使用Chunked编码，无需手动指定。
• 冗余请求头冲突：connection=keep-alive、host这类头属于HTTP底层连接管理字段，WebClient会自动处理，手动传入会干扰底层连接逻辑，导致连接提前关闭。

解决方案 #

方案1：过滤自动管理的请求头 #

修改头消费者，只保留业务相关头，跳过WebClient自动处理的字段：

Consumer<HttpHeaders> headersConsumer = headers -> {
    httpHeaders.forEach((key, value) -> {
        if (!key.equalsIgnoreCase(HttpHeaders.CONTENT_LENGTH)
            && !key.equalsIgnoreCase(HttpHeaders.CONNECTION)
            && !key.equalsIgnoreCase(HttpHeaders.HOST)) {
            headers.addAll(key, value);
        }
    });
};

方案2：只传递必要的自定义头 #

如果只有特定头需要传递，直接逐个指定，避免全量复制：

var responseMono = webClient
                  .post()
                  .uri(uri)
                  .header("postman-token", httpHeaders.getFirst("postman-token"))
                  .header("user-agent", httpHeaders.getFirst("user-agent"))
                  .header("accept-encoding", httpHeaders.getFirst("accept-encoding"))
                  .contentType(MediaType.APPLICATION_JSON)
                  .body(Mono.just(map), Map.class)
                  .exchangeToMono(response -> {
                     ref.set(response);
                     if (response.statusCode().equals(HttpStatus.OK)) {
                        return response.bodyToMono(String.class);
                     }
                     else {
                        return response.createException().flatMap(Mono::error);
                     }
             });

方案3：复制后移除冲突头 #

先复制所有头，再手动移除会引发冲突的字段：

var responseMono = webClient
                  .post()
                  .uri(uri)
                  .headers(headers -> {
                      headers.copyHeaders(httpHeaders);
                      headers.remove(HttpHeaders.CONTENT_LENGTH);
                      headers.remove(HttpHeaders.CONNECTION);
                      headers.remove(HttpHeaders.HOST);
                  })
                  .body(Mono.just(map), Map.class)
                  .exchangeToMono(response -> {
                     ref.set(response);
                     if (response.statusCode().equals(HttpStatus.OK)) {
                        return response.bodyToMono(String.class);
                     }
                     else {
                        return response.createException().flatMap(Mono::error);
                     }
             });

内容的提问来源于stack exchange，提问作者Kryptix