Hi,
In looking at things to simplify, I am now checking the support for
Property subtypes. Example:
@MaxLength( 50 )
interface Name
extends Property<String>
{
}
---
The idea here is that you can declare "Name name()" in many places, and
it will apply the same constraints, i.e. "it's a string property with
max length 50".
When looking through the code I find two issues with this:
1) It is REALLY hard to separate between the notion of "value" and
"property of value". One of the key usages, for example, is by Niclas
in the logging library, where he himself confuses this and so created a
Property<LogType> even though LogType is a property subtype already. A
simple enum performed the same task, but much clearer.
2) It is also not clear how clients are supposed to instantiate these
for setting the properties. With the above, you cannot really create a
LogType unless you first create a value with it, set it, and then take
the property-with-value from the LogType. But then taking it gets all
complicated when an Entity-internal LogType property is to be updated
with a LogType property coming from an external Value. Messy beyond belief.
And so, there seems to be at least three better ways to accomplish what
Property subtypes were supposed to do:
1) Use enums
2) Use composite domain-specific constraints:
@ConstraintDeclaration
@Retention( RetentionPolicy.RUNTIME )
@MaxLength(50)
public @interface Name {}
Which then is used as:
@Name Property<String> name();
or in method calls:
void changeName(@Name String newName);
3) Create a ValueComposite:
interface Fullname
extends ValueComposite
{
@Name Property<String> givenName();
@Name Property<String> surName();
}
---
So, considering this I am therefore removing the support for Property
subtyping. This will also make it easier to see in code exactly what a
method is for ("Property<String> name()" is immediately identified as a
Property declaration, whereas "Name name()" isn't).
I hope this is ok with everyone.
/Rickard
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