Entry set of read-only HttpHeaders loses original headers' ordering

[wilkinsona]

Affects: 5.1.9.RELEASE

The entry set returned from the result of calling HttpHeaders.readOnlyHttpHeaders(HttpHeaders) does not maintain the original headers' ordering. This is a regression from 5.1.0 that I think was introduced in 5.1.1 in ce7278a. I believe the set is unordered due to the use of Collectors.toSet() which creats an unordered Set:

spring-framework/spring-web/src/main/java/org/springframework/http/ReadOnlyHttpHeaders.java

Line 146 in 1ea6ce7

.collect(Collectors.toSet()));

[sbrannen]

Thanks for bringing this to our attention.

Your analysis is spot on, and the fix is as easy as .collect(Collectors.toCollection(LinkedHashSet::new))).

Edit: it actually turned out to be ever so slightly more complicated than that due to type inference. The above works in Eclipse but fails in the Gradle build using the Oracle JDK. 🤦‍♂

I'll push that to 5.1.x and master soon.