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[jsonb-spec users] [jsr367-experts] Re: Re: Re: Re: [2-DefaultMapping] Proposal

From: Eugen Cepoi <cepoi.eugen_at_gmail.com>
Date: Sun, 22 Feb 2015 10:19:32 -0800

It can be achieved with jsonb.fromJson(json, JsonObject.class).

About "Would be a shortcut for a unique use case not so common...but why
not... " I changed my mind :P adding this method is not useful. We see T in
your example, so the user knows what type he wants, but then why don't pass
it to fromJson.
 Le 22 févr. 2015 00:35, "Oleg Tsal-Tsalko" <oleg.tsalko_at_gmail.com> a écrit
:

> Hi Eugen,
>
> What do you mean that below already covered by existing methods?
>
> >>> public JSONObject fromJson(String str) throws JsonbException; // Not
> necessary exactly JSONObject class but just an idea
>
> 2015-02-21 23:10 GMT+02:00 Eugen Cepoi <cepoi.eugen_at_gmail.com>:
>
>> Hey Oleg,
>>
>> Le 21 févr. 2015 12:29, "Oleg Tsal-Tsalko" <oleg.tsalko_at_gmail.com> a
>> écrit :
>> >
>> > Hi guys,
>> >
>> > I'm from Kiev JUG and we (together with Olena Syrota and Andrii
>> Rodionov) decided to take part in JSON-B spec efforts.
>> > Hopefully our involvement will be useful for our collective success.
>> > We've reviewed work done so far and have some comments/suggestions that
>> I'll send in separate email a bit later.
>> >
>> > Right now just couple of my thoughts near default mapping examples
>> provided by Martin Vojtek and discussion above:
>> > 1) Agree that we should address and discuss parametrized types usage
>> separately from main basic scenarios. However it might be really good idea
>> to pass TypeToken<T> or smith similar instead of Class<T> params to
>> fromJson(...) methods to pass type information in runtime as proposed in
>> separate email thread.
>>
>> Yes but rather both instead of only typetoken, as the common scenario is
>> deser to a pojo.
>>
>> > 2) Reg basic scenarios, I can see two diff ways how unmarshalling will
>> be used in general by end users:
>> >>
>> >> a) To unmarsall JSON snippet into concrete domain class (as supported
>> by current methods in Jsonb interface)
>> >>
>> >> b) To unmarshall JSON into generic/default objects structure. I like 2
>> proposed variants here:
>> >>>
>> >>> public <T> T fromJson(String str) throws JsonbException; // assume
>> Object.class as a type
>>
>> Would be a shortcut for a unique use case not so common...but why not...
>> >>>
>> >>> public JSONObject fromJson(String str) throws JsonbException; // Not
>> necessary exactly JSONObject class but just an idea
>>
>> Hum, it is already covered by the existing methods.
>>
>> > Thus adding whole lot of specific methods like:
>> >>
>> >> public <T> List<T> fromJsonList(String str, Class<T> type) throws
>> JsonbException;
>> >>
>> >> public <T> Map<String, T> fromJsonMap(String str, Class<T> type)
>> throws JsonbException;
>> >>
>> >> public <E extends Enum<E>> EnumSet<E> fromJsonEnumSet(String str,
>> Class<E> type) throws JsonbException;
>> >>
>> >> public <E extends Enum<E>, T> EnumMap<E, T> fromJsonEnumMap(String
>> str, Class<E> enumType, Class<T> valueType) throws JsonbException;
>> >
>> > looks overcomplicated and redundant for me and I don't see much benefit
>> from it as for end users.
>> >
>>
>> Ouch, missed those... I agree 100%, don't add this kind of methods.
>>
>> > Thank you,
>> > Oleg
>> >
>> > 2015-02-18 14:26 GMT+02:00 Martin Vojtek <martin.vojtek_at_oracle.com>:
>> >>
>> >> Hi Przemyslaw,
>> >>
>> >> thank you very much for going through the examples.
>> >>
>> >> comments below.
>> >>
>> >> Cheers,
>> >> Martin
>> >>
>> >>> On 17 Feb 2015, at 20:40, Przemyslaw Bielicki <pbielicki_at_gmail.com>
>> wrote:
>> >>>
>> >>> Hi Martin,
>> >>>
>> >>> thanks for sharing this.
>> >>>
>> >>> First comment is the same I made to MartiNG: I would appreciate your
>> test in a form of JUnit test. You put a lot of effort in this and you will
>> have to rewrite / refactor a lot of code to make it unit test after all.
>> Yes, I know it should not and does not run but I just don't see the value
>> of main() method instead of proper JUnit class(es) - (you even implemented
>> your own assertEquals method - don't want to be impolite but it just does
>> not make sense :).
>> >>>
>> >>
>> >> according to JUnit, I am not sure if it is correct to define standard
>> in terms of non-standard tools. I will also participate in reference
>> implementation and JUnit is the most appropriate choice for testing
>> framework. These examples serve the purpose of discussion ground, and maybe
>> will not be part of the published standard, so this rule could be relaxed.
>> I need to think about it a bit.
>> >>
>> >>> I don't understand these lines:
>> >>>
>> >>> Map<String, Object> map =
>> (LinkedHashMap<String,Object>)jsonb.fromJson("{\"name\":\"unknown
>> object\"}", Object.class);
>> >>>
>> >>> Collection<Object> collection =
>> (ArrayList<Object>)jsonb.fromJson("[{\"value\":\"first\"},
>> {\"value\":\"second\"}]", Object.class);
>> >>>
>> >>> Why did you use Object.class parameter instead of Map.class and
>> Collection.class accordingly?
>> >>>
>> >>
>> >> The reason behind Object.class is that I want to show support for
>> Object.class. The alternative is to throw some Exception for this case.
>> There is also use case, when I want to allow user to specify Object.class,
>> and unmarshal whatever valid json. If this json is list, the result will be
>> Collection (specifically ArrayList of Objects), or Map (specifically
>> LinkedHashMap<String, Object>).
>> >>
>> >>> This is kind of verbose (IMO unnecessarily):
>> >>>
>> >>> EnumSet<Language> languageEnumSet1 =
>> (EnumSet<Language>)jsonb.fromJson("[\"Slovak\", \"English\"]",
>> DefaultMapping.class.getField("languageEnumSet").getType());
>> >>>
>> >>> EnumMap<Language, String> languageEnumMap1 = (EnumMap<Language,
>> String>)jsonb.fromJson("[\"Slovak\" : \"sk\", \"Czech\" : \"cz\"]",
>> DefaultMapping.class.getField("languageEnumMap").getType());
>> >>>
>> >>> I would change it to:
>> >>>
>> >>> EnumSet<Language> languageEnumSet1 = jsonb.fromJson("[\"Slovak\",
>> \"English\"]", languageEnumSet.getClass());
>> >>> EnumMap<Language, String> languageEnumMap1 = (EnumMap<Language,
>> String>)jsonb.fromJson("[\"Slovak\" : \"sk\", \"Czech\" : \"cz\"]",
>> languageEnumMap.getClass());
>> >>>
>> >>> this also requires adding static keyword to languageEnumSet and
>> languageEnumMap fields.
>> >>>
>> >>
>> >> In this case, getClass() returns concrete class (e.g. RegularEnumSet).
>> Reflection deals with class files, so the result is EnumSet.
>> >>
>> >> Intention of this code was to try to not to deal with generics, but to
>> show I want to provide generic type. Unfortunately use of reflection in
>> this case is also wrong, because the result will be EnumSet<E>.
>> >>
>> >> I can put there some not supported hack like this, but the discussion
>> about generics should be in separate thread:
>> >>
>> >> ParameterizedType parameterizedType = (ParameterizedType)new
>> HashSet<EnumSet<Language>>() {}.getClass().getGenericSuperclass();
>> >> EnumSet<Language> languageEnumSet =
>> (EnumSet<Language>)jsonb.fromJson("[\"Slovak\", \"English\"]",
>> parameterizedType.getActualTypeArguments()[0]);
>> >>
>> >>
>> >> Maybe the best way is to put there getClass() proposed by you. (and
>> not deal with generics in default mapping examples).
>> >>
>> >>> In the inheritance test the input and output JSONs are not the same:
>> >>> {"age":5, "dog":{"name":"Rex"}}
>> >>> vs.
>> >>> {"age":5,"name":"Rex"}
>> >>>
>> >>> it's a typo?
>> >>>
>> >>
>> >> It’s a typo, should be
>> >>
>> >> Dog animal = jsonb.fromJson("{\"age\":5, \"name\":\"Rex\"}}",
>> Dog.class);
>> >>
>> >>
>> >>> Expect few more comments from my side. I'm short in time this week,
>> thus I need to split my email into smaller pieces.
>> >>>
>> >>> Cheers,
>> >>> Przemyslaw
>> >>>
>> >>> On Fri, Feb 13, 2015 at 8:26 PM, Martin Vojtek <
>> martin.vojtek_at_oracle.com> wrote:
>> >>>>
>> >>>> Hi,
>> >>>>
>> >>>> I have pushed new branch default_mapping, which contains initial
>> examples for default mapping.
>> >>>>
>> >>>> There are also comments, which contain information about concepts
>> like null handling and default field access strategy.
>> >>>>
>> >>>> Default mapping of dates and generics handling is not part of this
>> commit and will be addressed separately.
>> >>>>
>> >>>> Looking forward to your feedback.
>> >>>>
>> >>>> Thank you,
>> >>>> Martin Vojtek
>> >>>
>> >>>
>> >>
>> >
>>
>
>