Hi guys,
The idea was that this "javaType" (name is subject to change) wouldn't
be included in all cases. Default behaviour should be to serialize as
small / easy as possible. Only if the type information is needed to
determine the actual type, an @JsonbTypeInfo annotation could be added
to the corresponding type. Configuring a "forceTypeInfo" boolean for the
programmatic JSONB config could be possible though.
@Przemyslaw:
Even if you solely use DTOs for serialization (I won't agree that that's
a must for all situations) you can still have situations with subclasses
and more complex hierarchies -- we had that case in several projects,
also when using transfer objects to map the domain objects. "Flattening"
the type hierarchies as workaround is not always desired.
But the longer I think about your approach that enums could be used to
derive the type information (like JPA, yes) the more I like this idea as
it would be more generic (more difficult / more effort to configure, but
easier to apply to different technologies). We should investigate
further (with some examples) what approach could be the best fit for JSONB.
But I highly recommend that some functionality to determine polymorphic
types should be included in the spec.
@Romain:
The spec should in fact require the impl to check for "suitable" types
then, i.e. only types to which the actual property type can be assigned
to should be allowed, etc.
I like your idea to add a "Wrapper" to unwrap instances but let JSONB
still do the (de-)serialization. This could be helpful for more control
how the containing type (the List in my example) should be instanciated.
But it doesn't fully solve the polymorphism example in all cases, as the
implementation of the actual type (Customer or VipCustomer) can still
not determined from the nested JSON objects if there is no such thing as
a JSON meta type information.
Cheers,
Sebastian
On 03/21/2016 08:32 AM, Przemyslaw Bielicki wrote:
> Hi,
>
> I'm not a fan of the original idea (and it's an euphemism). Remember
> that JSONB is used to serialize/deserialize DTOs, not domain objects.
> You should have an additional adapter layer to convert DTOs into
> application's business model/domain objects and back.
> Polymorphism is broken (yeah, it's another topic and more philosophic)
> and I would discourage its application in DTO layer. If you have to,
> you can use an enum to mark what's the target class (check JPA for
> additional inspirations). "//javaType": "x.y.z" is really bad idea IMO
> - what if you use the same JSON to communicate with applications
> developed in .net, python, php, c++ at the same time? (yes, it
> happens). Would you define a type for each platform?
>
> If you use DTOs in business layer, you're doing something wrong :)
>
> @Romain, your idea looks interesting, can you show and example or
> deserialization process where polymorphism is involved?
>
> Cheers,
> Przemyslaw
>
> On Sun, Mar 20, 2016 at 10:52 PM, Romain Manni-Bucau
> <rmannibucau_at_tomitribe.com <mailto:rmannibucau_at_tomitribe.com>> wrote:
>
> Hi guys
>
> Why not allowing adapters to wrap and unwrap instances but keep
> serializer mecanism. For serialization no issue but for
> deserialization we need to switch the deserialized type and then
> post process the instance - or do it automatically with an
> Unwrappable interface?
>
> Overall idea for this particular use case would be:
>
> X ----TypedWrapper(X)----> JSON
> JSON----TypedWrapper.class----> TypedWrapped ----unwrap----> X
>
> Parts in arrows are adapter/jsonb integration.
>
> An alternative is to provide to adapters the stream and jsonp
> instances to do it themself with probably a mapper reference to
> re(de)serialise an object directly.
>
> Wdyt?
>
> ---------- Message transféré ----------
> De : "Romain Manni-Bucau" <rmannibucau_at_tomitribe.com
> <mailto:rmannibucau_at_tomitribe.com>>
> Date : 19 mars 2016 21:49
> Objet : Re: [jsonb-spec users] Java polymorphism support
> À : <users_at_jsonb-spec.java.net <mailto:users_at_jsonb-spec.java.net>>
> Cc :
>
> Hi Sebastian
>
> I am not fan of that - Mark knows ;) - and in particular now I'm
> sure we shouldnt do it: the 0-day vulnerability is still there and
> you open the door to the same issue or a complicated config adding
> this feature in something as generic as jsonb.
>
> Le 19 mars 2016 21:28, "Sebastian Daschner"
> <java_at_sebastian-daschner.de <mailto:java_at_sebastian-daschner.de>> a
> écrit :
>
> Hi experts,
>
> I don't know whether this has been discussed in the mailing
> list before
> but a needed functionality would be to specify the Java type of
> properties in the serialized JSON.
>
> As JSON doesn't standardize comments or other "attributes"
> (like XML
> does) a "magic property" could be added.
>
> Please see the proposal (explored by Mark Struberg, Reinhard
> Sandtner
> and myself) on my blog:
> https://blog.sebastian-daschner.com/entries/json_mapping_polymorphism_support
>
> WDYT?
>
>
> Cheers,
> Sebastian
>
>