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".
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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