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https://issues.apache.org/jira/browse/ISIS-2695?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17350962#comment-17350962
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Daniel Keir Haywood commented on ISIS-2695:
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Adding this to 2.0.0, though if it slips then it slips.
> Add Java Bean Validation support
> --------------------------------
>
> Key: ISIS-2695
> URL: https://issues.apache.org/jira/browse/ISIS-2695
> Project: Isis
> Issue Type: Improvement
> Components: Isis Applib (programming model), Isis Core, Isis
> Persistence JDO, Isis Persistence JPA
> Affects Versions: 2.0.0
> Reporter: Patrick Deenen
> Priority: Major
> Fix For: 2.0.0
>
>
> [~danhaywood]
> In v2 we support meta-annotations, which can then have both Isis and also JDO
> annotations against them. That will make for better modularity.
> What's not clear right now is whether it's worth the boilerplate without an
> actual use case to benefit from that boilerplate. The only use case in
> practice in many cases is for a string property, eg name, where we want to
> tell both Isis and JDO that the max length is 50, say.
> Another use case could be for regex's, eg for a reference. That is the
> beginning of some business logic, and could use @Property(regexPattern=...)
> and [@parameter|https://issues.apache.org/parameter](regexPattern=...).
> More generally, we can do @Property(mustSatisfy=...) and
> [@parameter|https://issues.apache.org/parameter](mustSatisfy=...) for
> arbitrary business logic.
> Another consideration is if the property appears as a parameter in lots of
> actions; in which case this allows having to specify @Parametr and
> @ParameterLayout everywhere.
> For this particular use case, suggest just inline and get rid of NameType
> ("yagni" - "you ain't gonna need it", in other words).
> Perhaps the tipping point is if we could see there being a value type in the
> future... in which case a meta-annotation as being fairly close to that.
> Whether a value type / meta-annotation is worth the overhead depends on a
> couple of factors: one might be whether the concept itself is helpful to have
> as part of the ubiquitous language, another more practical reason is whether
> the entities that have properties of that value type are mutable (for that
> value type): eg does a Fixed Asset's name ever change? If so, a value type
> for 'Name' might start to make sense.
>
> [~ppjdeenen]
> I prefer using standards first and foremost, e.g. i would recommend switching
> to java bean validation which has default annotations for this. It has strong
> spring boot support, see
> [https://reflectoring.io/bean-validation-with-spring-boot/] Hence for String
> length validation use annotation
> [@size|https://issues.apache.org/size](max=50) for regex use annotation
> @pattern(regexp = "^[0-9]\{1,3}\.[0-9]\{1,3}\.[0-9]\{1,3}\.[0-9]\{1,3}$") for
> business logic in the entity use @AssertTrue or @AssertFalse and of course
> one can define custom (generic) annotations.
>
> [~danhaywood]
> We could certainly do this, though would require a contribution to Apache
> Isis itself to 'teach' it about the meanings of this. I think this would be a
> good and discrete thing to look into.
> Indeed, we do still have (very old) tickets for this:
> * https://issues.apache.org/jira/browse/ISIS-491
> * https://issues.apache.org/jira/browse/ISIS-517
> fyi, as a matter of style, we did use to have lots of fine-grained
> annotations similar to [@size|https://issues.apache.org/size] and @pattern.
> The difficulty we found was remembering them all, which is why we switched to
> using two annotations (one domain, one layout) for each member type ... ie
> @Property/@PropertyLayout,
> [@action|https://issues.apache.org/action]/@ActionLayout etc.
>
> [~ppjdeenen]
> Ok, to summarize my take on this:
> * Use java bean validation for validation of business logic (the java
> standard for validations) in combination with Spring for additional ease of
> use.
> * Refactor Apache Isis to support Java Bean Validation (so both Ises and ORM
> understand the same annotations)
> * Add @Property(Layout) and
> [@action|https://issues.apache.org/action](Layout) as custom Java Bean
> validation annotations
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