RFR: 8256363: Define toString() for MGF1ParameterSpec [v2]

[Weijun Wang]

On Mon, 16 Nov 2020 16:19:16 GMT, Sean Mullan <mullan at openjdk.org> wrote:

>> Weijun Wang has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   make PSSParameterSpec one line
>>   
>>   only in patch2:
>>   unchanged:
>
> src/java.base/share/classes/java/security/spec/MGF1ParameterSpec.java line 168:
> 
>> 166:     @Override
>> 167:     public String toString() {
>> 168:         return "MGF1:" + mdName;
> 
> I would replace "MGF1" or perhaps add "DigestAlgorithm" which is the name of the attribute. Is it necessary to print that this is an MGF1? PSSParameterSpec does not print that it is an RSASSA-PSS-params, and also prints "MGF", so it seems there would be some duplication. It almost seems like we should have some rules regarding how these parameters are printed out so everything is consistent.
> 
> Or perhaps it makes sense to have brackets around the fields. Otherwise when you chain several toStrings together, it makes it more difficult to discern when one field ends and the next begins. Hmm.

"MGF1" is only one kind of MGF and we might see "MGF2" in the future so it's worth printing out. Of course, `PSSParameterSpec` already has a `getMGFAlgorithm()` so the name can either be printed in the `toString` of the outer data type or the inner one.

As for `DigestAlgorithm` I don't think it's necessary because it's the only field for MGF1 so there's no ambiguity.

That said, we can try to provide some consistency here. If the types had been defined as records with
    static record MGF1Params(String messageDigest) {}
    static record PssParams(String messageDigest, String mgfAlgorithm,
            MGF1Params mgfParams, int saltLength, int trailerField) {}
The automatically generated `toString` would output something like
PssParams[messageDigest=SHA-1, mgfAlgorithm=MGF1, mgfParams=MGF1Params[messageDigest=SHA-1], saltLength=20, trailerField=1]
It's a little verbose. Do you like this style?

-------------

PR: https://git.openjdk.java.net/jdk/pull/1208