On Thu, Feb 10, 2022 at 3:08 AM 'Karsil' via jackson-user <
[email protected]> wrote:
> For now, we solved it like this:
>
> // BASE CLASS (now abstract)
> @JsonSubTypes( {
> @JsonSubTypes.Type( value = Child.class, name = Child.NAME )
> } )
> @JsonTypeInfo( use = JsonTypeInfo.Id.DEDUCTION )
> public abstract class BaseModel
> {
> // the rest as above
> }
>
> // CHILD
> @JsonInclude( JsonInclude.Include.NON_NULL )
> public class Child extends BaseModel
> {
> @JsonIgnore
> public static final transient String NAME = "child";
>
> // the rest as above
> }
>
> This can then be repeated for multiple childs, but you will have to pass a
> key with the value of the child, above "child".
>
Not sure I understand... making base class "abstract" sort of makes sense
(for it to be skipped).
But what do you mean by passing a "key"?
If you mean adding a new type property, wouldn't it make more sense to not
use DEDUCTION at all
but the standard, type id property based approach?
-+ Tatu +-
> Tatu Saloranta schrieb am Mittwoch, 9. Februar 2022 um 18:44:17 UTC+1:
>
>> On Tue, Feb 8, 2022 at 9:30 AM 'Karsil' via jackson-user
>> <[email protected]> wrote:
>> >
>> > Hey everyone,
>> >
>> > I'm trying to solve an inheritance problem where a clear deduction is
>> currently not possible. A toy example:
>> >
>> > // BASECLASS
>> > @JsonSubTypes( {
>> > @JsonSubTypes.Type( Child.class )
>> > } )
>> > @JsonTypeInfo( use = JsonTypeInfo.Id.DEDUCTION )
>> > public class BaseModel
>> > {
>> > @JsonProperty( value = "baseOne", required = true )
>> > @JsonPropertyDescription( "some value of base class" )
>> > protected String m_valueOne = "defaultValue";
>> >
>> > @JsonProperty( value = "basTwo", required = true )
>> > @JsonPropertyDescription( "another value of base class" )
>> > protected String m_valueTwo;
>> >
>> > public BaseModel()
>> > {
>> > }
>> >
>> > public BaseModel( final String p_value )
>> > {
>> > m_valueOne = p_value;
>> > }
>> > }
>> >
>> > // CHILD CLASS
>> > @JsonInclude( JsonInclude.Include.NON_NULL )
>> > public class Child extends BaseModel
>> > {
>> > @JsonProperty( value = "childValueFirst", required = true )
>> > @JsonPropertyDescription( "some value of child class" )
>> > private String m_child;
>> >
>> > public Child()
>> > {
>> > }
>> >
>> > public Child( final String p_value )
>> > {
>> > m_child = p_value;
>> > }
>> > }
>> >
>> > // TEST
>> > public class TestDemo
>> > {
>> > @Test
>> > public void testDefault() throws JsonProcessingException
>> > {
>> > final List<BaseModel> l_list = Stream.of( new BaseModel(), new Child()
>> ).collect( Collectors.toList() );
>> >
>> > final ObjectMapper l_mapper = new ObjectMapper();
>> > final String l_json = l_mapper.writeValueAsString( l_list );
>> > System.out.println( l_json );
>> > final List<BaseModel> l_out = l_mapper.readValue( l_json, new
>> TypeReference<List<BaseModel>>()
>> > { } );
>> > }
>> > }
>> >
>> > Error message (during deserialization):
>> > com.fasterxml.jackson.databind.exc.InvalidTypeIdException: Could not
>> resolve subtype of [simple type, class testproject.demo.BaseModel]: Cannot
>> deduce unique subtype of `testproject.demo.BaseModel` (2 candidates match)
>> >
>> > The error is quite logical: For the base class, two possibilities can
>> actually be deserialized.
>> >
>> > I already have encountered the defaultImpl property:
>> > @JsonTypeInfo( ..., defaultImpl = BaseClass.class )
>> > But this leads to a high-priority, default behaviour (all child objects
>> are deserialized with this default class, which is not intended). I'd
>> rather like to give it the lowest priority.
>> >
>> > But how actually to solve this? Thanks in advance for any help!
>>
>> I don't think this is possible at this point in time -- deduction
>> requires a unique set of properties.
>>
>> You could file an issue asking for an improvement here, outlining
>> details of how you think things should work
>> wrt. logic to use. There are a few issues like:
>>
>> https://github.com/FasterXML/jackson-databind/issues/3289
>>
>> related to this feature -- due to all limitations I am beginning to
>> wonder if this feature should not have been added
>> at all in its current form :-(
>> You may want to add a comment there.
>>
>> Basically everyone seems to have bit different ideas of logic to use,
>> and it is difficult to have centralized unified
>> logic to deal with this. As opposed to users maybe registering a
>> handler that operated on JsonNode of the full
>> content, or something (which is difficult to handle via
>> `@JsonTypeInfo`, processing model).
>>
>> Still, mr @drekbour might have some good ideas wrt this particular
>> aspect.
>>
>> -+ Tatu +-
>>
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