Hey Romain,
2015-03-13 11:38 GMT+01:00 Romain Manni-Bucau <rmannibucau_at_tomitribe.com>:
> Answered inline
>
> Le 13 mars 2015 08:28, "Inderjeet Singh" <inder_at_alumni.stanford.edu> a
> écrit :
> >
> > Don't force them, but let them use the library of their choice (Guava,
> Johnzon or any other) to create a Type object.
> >
>
> This is the original issue. For advanced cases (N levels of generics with
> N > 1) it is fine but for common cases (N =1) it sounds like a failure.
> Said otherwise why using an api which needs another one? Just use the
> complete one.
>
I understand your point but don't feel like it is a big issue. Anyway
everyone uses guava...
> > Using a constructed Type is an advanced use-case anyway. For example,
> with Gson, a majority of use-cases get handled without constructing a type
> ever.
> >
>
> Not fully agree. List and Map are super common (just think to crud). We
> can't rely on wrappers as for jaxb for json - just check how many people
> get rid of jettison for alternatives cause of it. Just makes it not natural
> so parameterized type are as common as classes for me.
>
I changed my mind and support the use of Type + some doc that explains to
the users how to obtain it (with Guava probably). It looks like the easiest
solution :) As Inder stated, if we had a TypeToken equivalent impl in std
jdk it would be great, but as we don't...
Cheers,
Eugen
>
> > Inder
> >
> > On Thu, Mar 12, 2015 at 11:49 PM, Romain Manni-Bucau <
> rmannibucau_at_gmail.com> wrote:
> >>
> >> We can't force a user to use a lib - or means the spec is not usable.
> >>
> >> Can be as simple as providing an implementation like
> JohnzonParameterizedType [1] which is trivial but solves this issue for
> most of cases - and several of remzining ones can be illegal (type variable
> etc).
> >>
> >> [1]
> https://git-wip-us.apache.org/repos/asf?p=incubator-johnzon.git;a=blob;f=johnzon-mapper/src/main/java/org/apache/johnzon/mapper/reflection/JohnzonParameterizedType.java;h=479268e451b88de3851dce48a97a0f6d29ca3b79;hb=dcc3a2c2a96d095251328740c03ebc0c053077c6
> >>
> >> - Romain
> >>
> >> Le 13 mars 2015 07:38, "Inderjeet Singh" <inder_at_alumni.stanford.edu> a
> écrit :
> >>
> >>> My recommendation will be that this API shouldn't provide any
> TypeLiteral.
> >>> For the users who need that support, should use Guava in conjunction
> with this.
> >>>
> >>> Inder
> >>>
> >>>
> >>> On Thu, Mar 12, 2015 at 2:50 PM, Romain Manni-Bucau <
> rmannibucau_at_tomitribe.com> wrote:
> >>>>
> >>>> Hi
> >>>>
> >>>> Type is really powerful but has one drawback: it is not working out
> of the box. This means we need to add a reflect package with basic
> implementations of some types in the api to make it a smooth api - at least
> ParameterizedType and maybe a list/set/map ones cause it is very common.
> Next issue we could hit is then we depend in the api of the jvm indirectly
> - interfaces get new method with jvm versions sometimes so what we can do
> is really bound to a jvm.
> >>>>
> >>>> That said i like the fact it avoids to introduce a new api and yet
> another type literal but just some common helper classes.
> >>>>
> >>>> - Romain
> >>>>
> >>>> Le 12 mars 2015 18:53, "Inderjeet Singh" <inder_at_alumni.stanford.edu>
> a écrit :
> >>>>
> >>>>> For Gson, we started with Type for pretty much the same reasons.
> Also because most developers are familiar with Type, and TypeLiteral is a
> new/advanced concept.
> >>>>>
> >>>>> Gson uses <T> T fromJson(String, Type) to avoid the need for
> casting. But it is unsafe, as you point out.
> >>>>> In practice though, I have not seen it to be a problem.
> >>>>>
> >>>>> TypeLiteral are very useful in JSON conversion, so we did end up
> adding it to Gson. Once we added it, I would have liked to revise
> fromJson() methods to use TypeLiterals instead of Type. But we couldn't do
> that for backward compatibility reasons.
> >>>>>
> >>>>> So, the point really is that if TypeLiterals are going to be added
> in a JSR, then it is better for JsonB to depend on that JSR and use
> TypeLiterals.
> >>>>>
> >>>>> But if you can't depend on the TypeLiteral JSR (if any), then go
> ahead and use Type. It works just fine.
> >>>>>
> >>>>> Inder
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>> On Thu, Mar 12, 2015 at 9:51 AM, Eugen Cepoi <cepoi.eugen_at_gmail.com>
> wrote:
> >>>>>>
> >>>>>> Hey Martin,
> >>>>>>
> >>>>>> 2015-03-12 17:21 GMT+01:00 Martin Vojtek <voytoo_at_gmail.com>:
> >>>>>>>
> >>>>>>> Hi Experts,
> >>>>>>>
> >>>>>>> I would like to open discussion about Generic Type Support in JSON
> Binding.
> >>>>>>>
> >>>>>>> The initial proposal is to add two methods to Jsonb interface:
> >>>>>>>
> >>>>>>> public <T> T fromJson(String str, java.lang.reflect.Type
> runtimeType) throws JsonbException;
> >>>>>>>
> >>>>>>> public String toJson(Object object, java.lang.reflect.Type
> runtimeType) throws JsonbException;
> >>>>>>>
> >>>>>>> (and analogically other methods with different input/output)
> >>>>>>>
> >>>>>>> Based on reviewing existing options, it does not appear there is a
> single optimal option.
> >>>>>>>
> >>>>>>> Reasoning behind java.lang.reflect.Type.
> >>>>>>>
> >>>>>>> There are several ways how to deal with generics:
> >>>>>>>
> >>>>>>> 1. To use java.lang.reflect.Type
> >>>>>>> 2. Use Type Literal (e.g. GenericType ...)
> >>>>>>> 3. Use Generic Type Builder
> >>>>>>>
> >>>>>>> It would be a lot of unnecessary code to build Generic Type
> Builder. And I think this should be not part of JSON Binding.
> >>>>>>>
> >>>>>>
> >>>>>> I agree with you.
> >>>>>>
> >>>>>>>
> >>>>>>> Type Literal may work in some cases, but generally it doesn't work
> (in infinite cases). It is also not backed by Java Language Specification
> and may not work in the future. For example, Type Literal doesn't work when
> used with lambdas or with some JVM languages different than Java.
> >>>>>>
> >>>>>>
> >>>>>> I understand but I think that it works in most use cases where it
> is needed. People use it to just deal with basic generics (custom or std
> types).
> >>>>>>
> >>>>>>>
> >>>>>>> I don't want to introduce yet another GenericType class and to
> duplicate code with some other specifications.
> >>>>>>
> >>>>>>
> >>>>>> I agree it is ugly :( would have been better if there was a similar
> thing as TypeToken from guava in std java (even if it is a hack in some
> way).
> >>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>> Use of java.lang.reflect.Type seems like the best choice from bad
> choices available. Integration with JAX-RS will be flawless, it is upon the
> user to build java.lang.reflect.Type (hopefully with the help of JSON
> Binding implementation).
> >>>>>>>
> >>>>>>> User can use already available Type Literal classes available in
> the Java ecosystem.
> >>>>>>
> >>>>>>
> >>>>>> Good point and most people already use guava. Only downside will be
> the untyped result of the fromJson.
> >>>>>> Here we can avoid user cast by doing : <T> T fromJson(String,
> Type), but it is definitely unsafe.
> >>>>>>
> >>>>>> Might be interesting to have Inderjeets feedback on how it was when
> they were using type and TypeToken.
> >>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>> Examples and pdf proposal are available at
> >>>>>>>
> >>>>>>>
> https://java.net/projects/jsonb-spec/sources/git/content/spec/spec.pdf?rev=da7db533076856699cec49a4eebd300b9f4a7230
> >>>>>>>
> >>>>>>>
> https://github.com/json-binding/spec/blob/default_mapping/examples/runtime/src/main/java/examples/mapping/DefaultMappingGenerics.java
> >>>>>>>
> >>>>>>> Looking forward to your feedback.
> >>>>>>>
> >>>>>>> MartinV
> >>>>>>
> >>>>>>
> >>>>>
> >>>
> >
>