ADBA Add type safe newFactory method

[Lance Andersen]

We definitely want  the string based version.

having both factory methods is also OK.  including  an unWrap method is also an option

> On Jul 19, 2018, at 11:07 AM, Douglas Surber <douglas.surber at oracle.com> wrote:
> 
> I don’t have a strong argument one way or the other. Both String and Class seem fine. The most recent push takes a String but I have no objection to changing it if there is a good reason. I’m in no position to judge how significant an "elegant Kotlin reified generic type extension function” would be. 
> 
> Douglas
> 
>> On Jul 18, 2018, at 2:57 PM, Frédéric Montariol <frederic.montariol at gmail.com> wrote:
>> 
>> I really like the alternative newFactory static method taking a Class parameter :
>> public static <T extends DataSourceFactory> T newFactory(Class<T> clazz) 
>> It would allow elegant Kotlin reified generic type extension function !
>> 
>> But there is something I don't like, this is the fact that DataSourceFactory.newFactory returns null if no corresponding class is found, causing NPE on next method call : factory.builder()
>> I would prefer if it throws an Exception.
>> 
>> Le ven. 13 juil. 2018 à 19:48, Douglas Surber <douglas.surber at oracle.com <mailto:douglas.surber at oracle.com>> a écrit :
>> The internal consensus is to change the spec exactly as you suggest and require the explicit cast if that’s what the user wants. I still would like to hear what others think.
>> 
>>  public static DataSourceFactory newFactory(String name) { … }
>> 
>>  DataSourceFactory factory = DataSourceFactory.newFactory(“my.adba.MyFactory”);
>> 
>> or 
>> 
>>  MyFactory factory = (MyFactory) DataSourceFactory.newFactory(“my.adba.MyFactory”);
>> 
>> Douglas
>> 
>> 
>> 
>>> On Jul 13, 2018, at 9:46 AM, Douglas Surber <douglas.surber at oracle.com <mailto:douglas.surber at oracle.com>> wrote:
>>> 
>>> This is a good question. I defined it the way I did specifically to avoid the explicit cast. I have no strong opinion on which is better. I’ll ask for opinions internally and I hope other members of this list give their thoughts.
>>> 
>>> Douglas
>>> 
>>>> On Jul 13, 2018, at 8:26 AM, Mark Rotteveel <mark at lawinegevaar.nl <mailto:mark at lawinegevaar.nl>> wrote:
>>>> 
>>>> The existing DataSourceFactory.newFactory(String name) has an unchecked cast using a (possibly inferred) type parameter.
>>>> 
>>>> Would it make sense to add an alternative with the signature:
>>>> 
>>>> public static <T extends DataSourceFactory> T newFactory(Class<T> clazz)
>>>> 
>>>> When you use this, you are tied to an ADBA implementation at compile time, but it will make this more type-safe.
>>>> 
>>>> And maybe the unchecked cast (and type parameter) should be removed from the variant taking a name only.
>>>> 
>>>> That is, change the method to
>>>> 
>>>> public static DataSourceFactory newFactory(String name) {
>>>>  if (name == null) throw new IllegalArgumentException("DataSourceFactory name is null");
>>>>  return ServiceLoader
>>>>          .load(DataSourceFactory.class)
>>>>          .stream()
>>>>          .filter(p -> p.type().getName().equals(name))
>>>>          .findFirst()
>>>>          .map(Provider::get)
>>>>          .orElse(null);
>>>> }
>>>> 
>>>> Any casts would then be the explicit responsibility of the developer, instead of accidental due to type inference.
>>>> 
>>>> Mark
>>>> -- 
>>>> Mark Rotteveel
>>> 
>> 
> 

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 <http://oracle.com/us/design/oracle-email-sig-198324.gif>Lance Andersen| Principal Member of Technical Staff | +1.781.442.2037
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