RFR: 8263506: Make sun.net.httpserver.UnmodifiableHeaders unmodifiable [v2]

[Julia Boes]

On Mon, 22 Mar 2021 16:41:10 GMT, Daniel Fuchs <dfuchs at openjdk.org> wrote:

>> Actually, I just noticed that the `List<String>`s are still modifiable. The constructor might have to create an intermediate `Map<String,List<String>>` with unmodifiable Lists and then you create an unmodifiable Map from that. 
>> 
>> As regards the comment above, yes you want to maintain that behavior. Could you normalize the key here and then just return `map.get(key).get(0)` (with suitable null checks)?
>
> Argh. Good catch Michael.  So now we'd also have to reimplement values(), entrySet(), and get() to wrap things into unmodifiableList... Or could we get away with providing an immutable snapshot instead of an immutable view? (we don't need to normalize anything though since the normalization is done already by the header's object wrapped in the UnmodifiableMap)

Thanks for catching that. The `List<String>` is now wrapped in an unmodifiable map, and some cases were added to the test.

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PR: https://git.openjdk.java.net/jdk/pull/3032