Character encoding is reset when setting Content-Type

[hiji]

Jetty version(s)

12.0.0

Jetty Environment

ee10

Java version/vendor (use: java -version)

openjdk version "17.0.8" 2023-07-18
OpenJDK Runtime Environment Temurin-17.0.8+7 (build 17.0.8+7)
OpenJDK 64-Bit Server VM Temurin-17.0.8+7 (build 17.0.8+7, mixed mode)

OS type/version

macOS 13.4.1

Description

If the character encoding of HTTP response (HttpServletResponse) is set by setCharacterEncoding method and Content-Type that does not include charset (e.g. text/html) is set, the character encoding set by setCharacterEncoding method will be used as the charset of Content-Type.

However, if you set same Content-Type (e.g. text/html) again, the character encoding set by setCharacterEncoding method will be reset and a different Content-Type will be set.

Checking the source code, onRemoveField is called when setting the set header again, but if the header is Content-Type, the character encoding is removed. (reference)

This is implemented in #9927 in 12.0.0.beta3, so it doesn't happen in 12.0.0.beta2 and earlier.

How to reproduce?

Perform the following processing in Servlet.

1. set character encoding with response.setCharacterEncoding.
2. set Content-Type that does not include charset with response.setContentType.
3. perform same process again as step 2.

For example, the following code.

response.setCharacterEncoding(StandardCharsets.UTF_8.name());
response.setContentType("text/html"); // Content-Type after processing is "text/html;charset=utf-8"
response.setContentType("text/html"); // Content-Type after processing is "text/html;charset=iso-8859-1"

[gregw]

I've reproduced a problem, but after the second set I get "text/html;charset=null". Anyway, looking!

[hiji]

@gregw
Thank you for confirming.
After checking again, the charset after calling setContentType method was definitely null.
In environment I confirmed, Result was output using getWriter method after that, but getCharacterEncoding method was called in getWriter method, and default character encoding iso-8859-1 was set.
(that code is here)

So the correct state is as follows.

response.setCharacterEncoding(StandardCharsets.UTF_8.name());
response.setContentType("text/html"); // Content-Type after processing is "text/html;charset=utf-8"
response.setContentType("text/html"); // Content-Type after processing is "text/html;charset=null"

[gregw]

This has been fixed by #10358