RFR: 8268960: com/sun/net/httpserver/Headers.java: Ensure mutators normalize keys and disallow null for keys and values [v3]

[Michael McMahon]

On Wed, 23 Jun 2021 18:02:02 GMT, Julia Boes <jboes at openjdk.org> wrote:

>> `com.sun.net.httpserver.Headers` normalizes its keys to adhere to the following format: First character uppercase, all other characters lowercase, for example `"foo" -> "Foo"`. This behaviour is not consistent across the mutator methods of the class, in particular `putAll()` and `replaceAll()` do not apply normalization.
>> 
>> The suggested fix is to update the implementation of `putAll()` and to add an implementation of of the java.util.Map default method `replaceAll()`. While here, we can improve `equals()` by adding a type check and add a `toString()` implementation.
>> 
>> Additionally,  the Headers class is updated to disallow null values for keys and values.
>
> Julia Boes has updated the pull request incrementally with one additional commit since the last revision:
> 
>   confirm HttpExchange::sendResponseHeaders fails if key/value null

Marked as reviewed by michaelm (Reviewer).

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PR: https://git.openjdk.java.net/jdk/pull/4528