Romain,
thanks for your ideas. As always, they are very valueable. 😊
I assume that a Deserializer would actually work and *workaround* the current
problem (which is fine for now). But my question really is: Isn't the word
"cardinality" missing in the Spec then? And what if I actually want to map a
collection to an int by let's say return the count of ist entries... (yes,
hypothethical, just to make you understand my point: this is nowhere forbidden
by the spec)?
The container level actually is there, but not visible to Johnzon: The adapter
actually does the cardinality change in its *implementation* (not in its
*declaration*), as it simply picks the first entry in the map. In fact I do not
find anything in JSON-B spec nor JavaDocs that both sides of the adapter MUST
have the same cardinality, as the spec and JavaDocs for adapters *just* say
that any umappable class has to be adapted to "just some" mappable class
(without a word about cardinality) -- and Map apparently *is* "just some"
mappable class.
Wdyt?
-Markus
-----Ursprüngliche Nachricht-----
Von: Romain Manni-Bucau <rmannibu...@gmail.com>
Gesendet: Dienstag, 1. Oktober 2019 16:24
An: dev@johnzon.apache.org
Betreff: Re: User Question: Complex Adapters
Hi Markus,
Map does not match Map.Entry so it does not work ;)
Semantically you miss a level of "container" (a map is a kind of
List<Map.Entry> even if structurally it does not match).
Also note that Map.Entry is modelized per its signatures as a {key:...,
value: ....} and not as {key:value} as in a map.
I guess a Deserializer can be closer than an adapter of what you are trying to
do.
Romain Manni-Bucau
@rmannibucau <https://twitter.com/rmannibucau> | Blog
<https://rmannibucau.metawerx.net/> | Old Blog
<http://rmannibucau.wordpress.com> | Github <https://github.com/rmannibucau> |
LinkedIn <https://www.linkedin.com/in/rmannibucau> | Book
<https://www.packtpub.com/application-development/java-ee-8-high-performance>
Le mar. 1 oct. 2019 à 16:17, Markus Karg <k...@quipsy.de> a écrit :
> I’d be very very glad if you could answer a short user question I’m
> completely stuck with. 😊
>
> Johnzon is able to parse JSON object into Java Map while respecting
> custom
> adapters:
>
> // Works well: Uses custom Adapter<UUID, String> Map<UUID, Foo> map =
> jsonb.fromJson("{ \"" + uuid + "\": { \"name\":
> \"Lala\" } }", new JohnzonParameterizedType(Map.class, UUID.class,
> Foo.class));
>
> Now let’s assume we do not want to get a complete Map but just a
> single Map.Entry, as we know for sure the JSON string only contains
> exactly just one single key-value-pair:
>
> JsonbConfig jsonbConfig = new JsonbConfig().withAdapters(new
> UuidAdapter(), new MapEntryAdapter<UUID, Foo>());
>
> // Fails with "Can't map Entry<UUID, Foo>"
> Map.Entry<UUID, Foo> entry = jsonb.fromJson("{ \"" + uuid + "\": {
> \"name\": \"Lala\" } }", new JohnzonParameterizedType(Map.Entry.class,
> UUID.class, Foo.class));
>
> public class MapEntryAdapter<K, V> implements
> JsonbAdapter<Map.Entry<K,
> V>, Map<K, V>> {
> @Override public Map<K, V> adaptToJson(Entry<K, V> obj) throws
> Exception { … }
> @Override public Entry<K, V> adaptFromJson(Map<K, V> obj) throws
> Exception { … } }
>
> Strange but true, this does not work but complains it cannot map
> Entry<UUID, Foo> -- it seems it cannot „see“ the correctly registered
> adapter (not even if I replace <K, V> by <UUID, String> manually in
> the code).
>
> So the question is: Where is the fault? Did I try something (what?)
> which is forbidden in JSON-B? Is this a bug in Johnzon?
>
> Actually I assume it is my personal fault (as so often), but I just
> cannot see where… 😉
>
> Thanks a lot for your kind help!
> -Markus
>
>
>
