Re: DDD Implementation: Marker interfaces for all classes
"Jan Bols [email protected] [domaindrivendesign]" <[email protected]> Mon, 15 Aug 2016 20:47:02 +0200
| Newsgroups | gmane.comp.programming.domain-driven-design |
|---|---|
| Message-ID | <CAHd+Bxy23NpTt7ORNdPN1eK3DWDh9vZHq-NwWxp=N743x-J5Uw@mail.gmail.com> |
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Hi Niklas,
if you really want to enforce that every written class implements some
marker interface (or have some annotation), you can do it as some compile
time check using aspectJ for example (see
https://www.jayway.com/2010/03/28/architectural-enforcement-with-aid-of-aspectj/
for a similar example).
However, developers won't like it and will find a way to fool or bypass the
system. Once they do that, it becomes a completely useless protocol they
have to follow when creating a new class.
And you can't blame them.
Not every code you write can be marked as a 'Repository' or 'ValueObject'
or 'Entity' or 'DomainService' or ... It's just too limited and it's not
what DDD tries to achieve. There's always other stuff that has nothing to
do with DDD. I think you should invest the time less into enforcing a
certain view and spend more time on training, pair programming and code
reviewing.
It's far more important that developers understand the business and use the
same language in their code than it is to know if something is a "domain
service" or an "application service", a "value object" or an "entity".
On the other hand it is useful to mark certain classes playing certain
roles as a "Repository" or "Aggregate Root". It's extra information that
helps you understand the code better. But please, don't enforce it.
Encourage them instead.
Greetings
Jan
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<div dir=3D"ltr">Hi Niklas,<div>if you really want to enforce that every=C2=
=A0written=C2=A0class implements some marker interface (or have some annota=
tion), you can do it as some compile time check using aspectJ for example (=
see=C2=A0<a href=3D"https://www.jayway.com/2010/03/28/architectural-enforce=
ment-with-aid-of-aspectj/">https://www.jayway.com/2010/03/28/architectural-=
enforcement-with-aid-of-aspectj/</a> for a similar example).</div><div><br>=
</div><div>However, developers won't like it and will find a way to foo=
l or bypass the system. Once they do that, it becomes a completely useless =
protocol they have to follow when creating a new class.=C2=A0</div><div><br=
></div><div>And you can't blame them.</div><div><br></div><div>Not ever=
y code you write can be marked as a 'Repository' or 'ValueObjec=
t' or 'Entity' or 'DomainService' or ... It's just =
too limited and it's not what DDD tries to achieve. There's always =
other stuff that has nothing to do with DDD. I think you should invest the =
time less into enforcing a certain view and spend more time on training, pa=
ir programming and code reviewing.</div><div><br></div><div>It's far mo=
re important that developers understand the business and use the same langu=
age in their code than it is to know if something is a "domain service=
" or an "application service", a "value object" or=
an "entity".</div><div><br></div><div>On the other hand it is us=
eful to mark certain classes playing certain roles as a "Repository&qu=
ot; or "Aggregate Root". It's extra information that helps yo=
u understand the code better. But please, don't enforce it. Encourage t=
hem instead.=C2=A0</div><div><br></div><div>Greetings</div><div>Jan=C2=A0</=
div></div>
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Posted by: Jan Bols <[email protected]> <hr style=
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