[bv-dev] On the support for Optional (was Re: Support for constraints on container values (e.g. Collection<@Email String>))

[Matt Benson]

On Mon, Nov 21, 2016 at 10:21 AM, Emmanuel Bernard
<emmanuel at hibernate.org> wrote:
> What’s the difference between a field and a getter based property?
> It is the same for all intended purposes in Bean Validation.

Point taken; I was thinking more of return values for business
methods, personally. But like Christian says, perhaps it's more
straightforward not to discriminate.

Matt

>
>> On 21 Nov 2016, at 15:51, Matt Benson <mbenson at apache.org> wrote:
>>
>> On Mon, Nov 21, 2016 at 8:18 AM, Gunnar Morling <gunnar at hibernate.org> wrote:
>>> Yes, probably we should not support Optional for fields. Also parameters are
>>> dubious (the JDK team discourages that afaik). But supporting it for return
>>> values (and getter-based properties) seems reasonable.
>>
>> +1
>>
>> Matt (with apologies for not having participated earlier in the spec
>> 2.0 process)
>>
>>>
>>> 2016-11-21 14:32 GMT+01:00 Emmanuel Bernard <emmanuel at hibernate.org>:
>>>>
>>>>
>>>> On 7 Nov 2016, at 23:42, Hendrik Ebbers <hendrik.ebbers at me.com> wrote:
>>>>
>>>> I don’t think that support for Optional is that important since having a
>>>> field of type Optional looks like an anti-pattern to me. Normally Optional
>>>> should be used as a method return type and not as a type for a field.
>>>> Supporting it in the bean validation might end in strange model classes.
>>>>
>>>> Example:
>>>>
>>>> The following model looks good to me:
>>>>
>>>> public class Model {
>>>>
>>>> @NotNull
>>>> private String name;
>>>>
>>>> public String getName() { return name; }
>>>>
>>>> public void setName(String name) { this.name = name; }
>>>>
>>>> public Optional<String> name() { return Optional.ofNullable(name);}
>>>>
>>>> }
>>>>
>>>> On the other hand this looks like an anti-pattern to me:
>>>>
>>>> public class Model {
>>>>
>>>> @NotNull
>>>> private Optional<String> name;
>>>>
>>>> public Optional<String> getName() { return name; }
>>>>
>>>> public void setName(String name) { this.name = Optional.ofNullable(name);
>>>> }
>>>>
>>>> }
>>>>
>>>>
>>>> Yes Optional on a property is deemed an anti pattern by the JDK team but
>>>> since Bean Validation supports contraints on method parameters and return
>>>> values, this is still a valid use case
>>>>
>>>> Optional<@Email String> getUserEmail(@NotNull UUID userId);
>>>>
>>>> Emmanuel
>>>>
>>>>
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>>>
>>>
>>>
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