I would initialize null or absent lists with empty collections when deserializing. For simple data types like string, long etc. this works with this setting.

However, as soon as I define my own class this no longer works.

class FooTest {
    
       @Autowired
       private ObjectMapper objectMapper;
    
       @Test
       void empty() throws JsonProcessingException {
    
          objectMapper.setDefaultSetterInfo( JsonSetter.Value.forValueNulls( Nulls.AS_EMPTY ) );
          final Foo foo = objectMapper.readValue( "{}", Foo.class );
          final Foo foo1 = objectMapper.readValue( "{\"items\": null,\"items1\": null}", Foo.class );
    
       }
    
       @JsonIgnoreProperties( ignoreUnknown = true )
       public class Foo {
    
          @JsonDeserialize( as = LinkedHashSet.class )
          private Set<String> items;
    
          @JsonDeserialize( as = LinkedHashSet.class )
          private Set<Bar> items1;
    
          @JsonCreator
          public Foo(
                @JsonProperty( "items" ) final Set<String> items,
                @JsonProperty( "items1" ) final Set<Bar> items1 ) {
             this.items = items;
             this.items1 = items1;
    
          }
       }
    
       @JsonIgnoreProperties( ignoreUnknown = true )
       public class Bar {
    
          @JsonCreator
          public Bar( ){
    
          }
       }
    }

Does anyone know why?