Hi Victor,
Put shortly, Allow is a disjunction (OR) whereas Require is a conjunction
(AND)
- @Allow({ ORACLE, POSTGRES }) means that you allow for both of these
dialects to be used in general. No other dialect may be used (e.g. MYSQL).
If an API supports only one of the two dialects, e.g. CONNECT BY (supported
by Oracle), then it is still allowed.
- @Require({ ORACLE, POSTGRES }) will now require *both* Oracle and
PostgreSQL support on any API. In this case, CONNECT BY will no longer
work, because it is not supported by PostgreSQL
In your case, you could just use @Allow(POSTGRES) only. You don't have to
Allow(DEFAULT), I don't think this adds much value. If you're only working
with a single RDBMS, you don't need @Require. But you could add it, and
then add a second dialect in the future, should you choose to support
another RDBMS.
Perhaps, code explains this better? Here's the implementation from
Tools.checkSQLDialect():
boolean allowedFail = true;
allowedLoop:
for (SQLDialect a : allowed) {
for (SQLDialect s : supported) {
if (a.supports(s)) {
allowedFail = false;
break allowedLoop;
}
}
}
if (allowedFail)
return error.apply("The allowed dialects in scope " + allowed + " do
not include any of the supported dialects: " + supported);
boolean requiredFail = false;
requiredLoop:
for (SQLDialect r : required) {
for (SQLDialect s : supported)
if (r.supports(s))
continue requiredLoop;
requiredFail = true;
break requiredLoop;
}
if (requiredFail)
return error.apply("Not all of the required dialects " + required + "
from the current scope are supported " + supported);
I hope this helps.
Lukas
On Fri, Aug 30, 2019 at 3:35 PM Victor Noël <[email protected]> wrote:
> Hi,
>
> I think I'm a bit thick with this, but I just can't wrap my head around
> the difference (and more importantly the need) for both Allow and Require
> annotations with jooq-checker.
>
> Maybe it's because my use case does not need both, so let me explain what
> it is:
> - I have some code (maybe used by different applications, so it's kind of
> library code) that do db related stuffs, and if it is possible, I want this
> code as generic as possible w.r.t. the database dialect
> - because I mostly use postgresql, sometimes I use postgresql-specific
> features (still in library code)
> - in some specific cases, I DO know which database I am using (disclaimer:
> it's postgresql :P) for my application (so it's not library code)
>
> What I did is annotate most of this code with `Allow(SQLDialect.DEFAULT)`
> and when it wasn't enough, I used `Allow(SQLDIALECT.POSTGRES)`.
>
> Some questions:
> - I'm not sure it is correct to use the DEFAULT dialect for this, but I
> suppose it is?
> - I don't see the need for Require here, is it only needed when I am
> working with multiple dialects (not DEFAULT) at the same?
> - Is Allow some kind of architecture-level rule while Require some kind of
> class-level assertion?
>
> Thanks for any help to understand this :)
>
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