[jira] [Resolved] (CAMEL-25526) camel-vertx-http - a header with several values (a List or an array, such as a repeated request header) is sent as one header with the value "[a, b]"

["Claus Ibsen (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CAMEL-25526?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Claus Ibsen resolved CAMEL-25526.
---------------------------------
    Resolution: Fixed

Fixed by https://github.com/apache/camel/pull/27689 (merged to main as c5419d1de0c9, 4.24.0).

_Claude Code on behalf of Claus Ibsen_

> camel-vertx-http - a header with several values (a List or an array, such as a repeated request header) is sent as one header with the value "[a, b]"
> -----------------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: CAMEL-25526
>                 URL: https://issues.apache.org/jira/browse/CAMEL-25526
>             Project: Camel
>          Issue Type: Bug
>          Components: camel-vertx-http
>            Reporter: shashank
>            Assignee: shashank
>            Priority: Major
>             Fix For: 4.24.0
>
>
> Correction (2026-10-12): an earlier version of this description said camel-http sends one header per value. It does not: {{HttpProducer.applyHeader}} sends two or more values as one header {{[a, b]}} (on purpose, see CAMEL-4212 and CAMEL-11662). The proposed change aligns camel-vertx-http with camel-netty-http and camel-undertow, which send one header per value; the statements about camel-http further down are wrong in that respect. Whether camel-vertx-http should follow camel-http or camel-netty-http/camel-undertow is a maintainer decision (see the pull request).
> {{DefaultVertxHttpBinding.populateRequestHeaders}} (lines 120-148 at main 586855a18315) copies each message header to the request with {{headers.set(key, tc.convertTo(String.class, headerValue))}}. For a header whose value is a collection, the String conversion is {{toString()}}, so {{List.of("a", "b")}} is sent as the single header line {{X-Test: [a, b]}}; a {{String[]}} is sent as {{[Ljava.lang.String;@7112ce6}}. The HTTP consumers (platform-http, undertow, servlet, netty-http, vertx-http's own responses) map a request header that occurs more than once to a List, so a route that forwards such a request with vertx-http (a proxy, or HTTP/2 clients that send each cookie in its own {{cookie}} header) sends corrupted header values, without any error.
> camel-http ({{HttpProducer}}), camel-netty-http and camel-undertow iterate the values with {{ObjectHelper.createIterator(value, null, true)}} and {{HttpUtil.applyHeader}} and send one header line per value, and a String as one value.
> h3. Reproduction
> New {{VertxHttpMultiValueHeaderTest}} (undertow test server as in the other tests, which echoes the values of {{X-Test}} it receives, joined with {{|}} when there are several): on main two of the three tests fail, twice:
> {noformat}
> sendsEachValueOfAListHeader: expected: <a|b> but was: <[a, b]>
> sendsEachValueOfAnArrayHeader: expected: <a|b> but was: <[L...@7112ce6>
> {noformat}
> The third test checks that a String with a comma ({{"a, b"}}) is still sent as one value (it passes before and after, and guards the "no delimiter" choice of the fix).
> h3. Proposed fix
> Iterate the header value as camel-http does ({{ObjectHelper.createIterator(headerValue, null, true)}} with {{HttpUtil.applyHeader}}, which applies the header filter per value and skips null values) and set all the values of the header. A String or any other single value is sent as before. 4.23 upgrade guide note added (a collection or array header now gives one header line per value). camel-vertx-http tests with the fix: 100, 0 failures (1 skipped, as on main).
> Found with a Lean 4 model of the header copy (a value is a String or a list of Strings): "a header is sent as one line per value" (camel-http) fails for {{["a", "b"]}}, and main is proved to be wrong for every list value (also a one-element list, sent as {{[a]}}). The fix is proved to equal camel-http's behaviour for every value and to send the same line as main for every String. Confirmed with the real producer.
> Not changed here: {{KnativeHttpProducer}} of camel-knative-http has the same {{toString()}} copy of the request headers (the reply headers of {{KnativeHttpConsumer}} already iterate the values).
> Affected: main, camel-4.22.x, camel-4.18.x, camel-4.14.x (same code, GitHub contents API).
> Duplicate check (2026-10-10): JIRA text "vertx-http" and "header" (44, none about multi-value headers; CAMEL-24424 was the REST header filter direction); GitHub pull requests "vertx-http header multiple values" (none). No open pull request changes {{DefaultVertxHttpBinding}}.
> _Filed with Claude Code on behalf of allthingssecurity._



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