Re: Sending data across the wire.

Jackson allows you to define custom un/marshalling mechanisms when needed
so you can control what gets included.

Years ago we had some code which allowed you to include/exclude
properties/paths to build up a JSON object to return
using read[Nested]Property().  Basically you'd explicitly define what you
wanted to include and it would build the JSON for you.  No idea if I still
have that code lying around somewhere, but the idea is fairly simple, I
think.

mrg


On Wed, Sep 18, 2019 at 2:21 AM Andrus Adamchik <[email protected]>
wrote:

> Ignoring serialization mechanics (and even the presence of Cayenne) for a
> moment, I was always wondering how do people even approach this problem.
> Every persistent object is potentially an entry point to a near-infinite
> graph of objects coming from DB. So you need to have a set of clear rules
> of how deep and wide you want to go when you start serializing.
>
> DTO is one way to define such rules. But unless your rules are very simple
> ("send the attributes, don't send the relationships"), if you start
> generating DTOs, they will have the same set of relationships. And you'd
> end up with the same issue as you had with serializing the original
> DataObjects.
>
> So what parts of the graph do you need to serialize?
>
> And if this needs to be flexible, I would probably write a small library
> that allows a user to define a subset of model to serialize, and then
> applies that "submodel" to DataObjects directly (this is the Agrest.io
> approach on a smaller scale). But as with any generic solution, this will
> require a bit of effort, dealing with edge cases, etc.
>
> Andrus
>
>
>
> > On Sep 18, 2019, at 12:29 AM, John Huss <[email protected]> wrote:
> >
> > It's a small effort to create a custom entity template to generate any
> kind
> > of entity class you want, for instance for a DTO. You can copy a lot of
> > stuff right out of the regular templates if you want.
> >
> > Then you can use maven or ant to easily regenerate those classes the same
> > way CayenneModeler does without having to change the custom template
> > selections all the time.
> >
> > On Tue, Sep 17, 2019 at 1:49 PM Tony Giaccone <[email protected]> wrote:
> >
> >> So typically I create a Data Transfer Object to return values across the
> >> wire that I have fetched and copy attributes from my model object to the
> >> DTO.  This gets tedious quickly.  I wondered if there's not another way
> >> that people are doing this, because this seems entirely too painful.
> >>
> >> However, if* this is* what most people do, then perhaps a change could
> be
> >> made to the modeler, that would all you to create automatically a set of
> >> DTO objects with when you generate the model objects.  I recognize that
> >> this would be a rather significant effort and I'm guessing that there's
> >> probably a better way, but I'm not aware of what it is.
> >>
> >> Any suggestions?
> >>
> >>
> >> Tony Giaccone
> >>
>
>