Custom converters (such as DateLongConverter via @DateLong) don't work with projections.

[LGDOI]

SDN v6.1.4 via Spring Data v2.5.4

We are migrating from OGM to SDN. In OGM @DateLong works well with COALESCE. However, in SDN the same causes an error.

Give following artifacts.

DashboardLite.java

import java.util.Date;
import lombok.Value;
import org.springframework.data.neo4j.core.support.DateLong;

@Value
public class DashboardLite {

  String id;

  @DateLong
  Date created;

  @DateLong
  Date updated;

  @DateLong
  Date modified;
}

DashboardRepository.java

Note that entity mapping type is Dashboard and return type is DashboardLite POJO

@Repository
public interface DashboardRepository extends Neo4jRepository<Dashboard, String> {
  @Query(value = "MATCH (dashboard:Dashboard {id: $dashboardId}) "
      + "RETURN dashboard, COALESCE(dashboard.updated, dashboard.created) AS modified;")
  Optional<DashboardLite> findLiteById(String dashboardId);
}

Test

  @Test
  fun findLiteById() {
    clean()
    val id = "dash-1"
    val dashboard = DashboardStub.getOne(id = id)
    dashboard.created = Date()
    dashboard.updated = Date()
    dashboardRepository.save(dashboard)

    assertingWith(dashboardRepository.findLiteById(id).get()) {
      assertThat(it.id).isEqualTo(id)
      assertThat(it.modified).isNotNull
    }
  }

Error

Caused by: org.springframework.core.convert.ConversionFailedException: Failed to convert from type [org.neo4j.driver.internal.value.IntegerValue] to type [java.util.Date] for value '1630075360851'; nested exception is org.neo4j.driver.exceptions.value.Uncoercible: Cannot coerce INTEGER to Java String
	at app//org.springframework.core.convert.support.ConversionUtils.invokeConverter(ConversionUtils.java:47)
	at app//org.springframework.core.convert.support.GenericConversionService.convert(GenericConversionService.java:192)
	at app//org.springframework.core.convert.support.GenericConversionService.convert(GenericConversionService.java:175)
	at app//org.springframework.data.neo4j.core.mapping.DefaultNeo4jConversionService.lambda$readValue$0(DefaultNeo4jConversionService.java:74)
	at app//org.springframework.data.neo4j.core.mapping.DefaultNeo4jConversionService.readValueImpl(DefaultNeo4jConversionService.java:96)
	... 128 more
Caused by: org.neo4j.driver.exceptions.value.Uncoercible: Cannot coerce INTEGER to Java String
	at app//org.neo4j.driver.internal.value.ValueAdapter.asString(ValueAdapter.java:91)
	at app//org.springframework.data.neo4j.core.convert.AdditionalTypes.asDate(AdditionalTypes.java:228)
	at app//org.springframework.data.convert.DefaultConverterBuilder$ConfigurableGenericConverter.convert(DefaultConverterBuilder.java:151)
	at app//org.springframework.core.convert.support.ConversionUtils.invokeConverter(ConversionUtils.java:41)
	... 132 more

Workaround

The same test pass by changing modified's data type from Date to long and remove @DateLong annotation.

//  @DateLong
  long modified;

Question

Should @DateLong convert COALESCE returned long to Date?

[michael-simons]

It does, but there are a couple of oddities here:

• The coalesed column wont be used for the attribute (entity mapper wont recognize it as part of the object)
• Some domain object seems to have java.util.Date attribute without @DateLong, otherwise the code branch would not reach the above point.

Please share the whole setup.

[michael-simons]

It is always great to have colleagues helping out to see what has been missed.

So what you are trying to do is to apply @DateLong (or in general, converters), to DTO based projections. This is currently not supported, that's the reason for the failure you seeing. I am gonna fix that.

Also, properties in the projection (your DashboardLite) that already exist in the domain and are annotated there, don't need to be annotated again. So the correct projection will be (with the enhancement in place)

import java.util.Date;
import lombok.Value;
import org.springframework.data.neo4j.core.support.DateLong;

@Value
public class DashboardLite {

  String id;

  Date created;

  Date updated;

  @DateLong
  Date modified;
}

[LGDOI]

Thank you Michael for suggesting not needing @DateLong on the properties that are defined in the entity class (Dashboard.java).