RFR: 8241306: Add SignatureMethodParameterSpec subclass for RSASSA-PSS params [v2]

[Weijun Wang]

On Tue, 30 Mar 2021 18:41:45 GMT, Sean Mullan <mullan at openjdk.org> wrote:

>> There are other fields in `RSASSAParams`, so if there is no DigestMethod, it will be SHA-256 but the other fields (like SaltLength or TrailerField) will still be read if they exist.
>> 
>> If there is no `RSASSAParams` at all or if it's empty, then the defaults will be returned.
>
> I wonder if the @implSpec is clear enough that this will be returned. I might suggest adding a similar @implSpec in this method that basically states what you said above.

I'm not sure if it's appropriate to specify the default value in this method. As long as there is an `RSAPSSParameterSpec` object, there must be a non-null `PSSParameterSpec` inside and it is the one that was used to construct this object.

I am thinking if we can append the following to the `@implNote` in the class spec:
 * One can obtain this default value using the following expression:
 * <pre><code>
 * XMLSignatureFactory.getInstance()
 *      .newSignatureMethod(SignatureMethod.RSA_PSS, null)
 *      .getParameterSpec()
 * </code></pre>

but this makes it more like an `@implNote` instead of an `@implSpec`.

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PR: https://git.openjdk.java.net/jdk/pull/3181