MapStruct : Setting value of now while mapping?

I am trying to set a DateTime field in my mapped classes using MapStruct, but could not see any example.

So, can I set a DateTime or Instant field value as now() while mapping from DTO to Entity? How can I do this? I tried something below:

@Mapper(componentModel = "spring", imports = {Instant.class})
public interface DemoMapper {

    @Mapping(source = "created", target = "created", defaultValue = Instant.now())
    Employee toEntity(EmployeeDto source);

    EmployeeDto toDto(Employee destination);
}

You can use defaultExpression in your mapping. It expects a string as an argument, with the following format:

"java(expression)"

Where expression is the expression you're looking for, so in your case

@Mapping(source = "created", target = "created", defaultExpression = "java(java.time.Instant.now())")

Notice that I used the fully qualified name for the Instant class, since defaultExpression can't know where Instant is (or at least it can't assume you want the one from the standard library), so it can't import it in the file it generates.