shashank created CAMEL-25526:
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Summary: 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
{{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:
<[Ljava.lang.String;@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: camel-knative-http has the same {{toString()}} copy in
{{KnativeHttpProducer}} and in the reply headers of {{KnativeHttpConsumer}}.
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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