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Strategy to check at runtime the null value with JSpecifiy #4105
Description
Use case
We have field that are null at object creation but a never null right after.
Example the field Id or CreatedAt on an entity. The field are nullable but on the ReadDto these field are not null.
I would like to be able to check at runtime that the field is not null with Objects.requireNonNull(...). It could be a new strategy for the mapping.
It may be possible with something like that:
@Mapping(target = "createdAt", nullValueCheckStrategy = NullValueCheckStrategy.AT_RUNTIME)
Generated Code
Having:
@Override
public ChangeRequestReadSimpleDto toChangeRequestDto2(ChangeRequest cr) {
ShiftRawId id = null;
ChangeRequestTypeDto type = null;
OffsetDateTime createdAt = null;
id = toRawShiftId(Objects.requireNonNull(cr.getId()));
type = convertEnum( cr.getType() );
OffsetDateTime createdAt = toOffsetTime(Objects.requireNonNull(cr.getCreatedAt()));
return new ChangeRequestReadSimpleDto(id, type, createdAt);
}Instead of:
@Override
public ChangeRequestReadSimpleDto toChangeRequestDto2(ChangeRequest cr) {
ShiftRawId id = null;
ChangeRequestTypeDto type = null;
OffsetDateTime createdAt = null;
id = toRawShiftId(cr.getId()); // Error cr.getId() is nullable
type = convertEnum( cr.getType() );
OffsetDateTime createdAt = toOffsetTime(cr.getCreatedAt()); // Error cr.getCreatedAt() is nullable
return new ChangeRequestReadSimpleDto(id, type, createdAt);
}Possible workarounds
Define a custom mapping with the expression:
@Mapping(target = "createdAt", expression = "java(toOffsetTime(java.util.Objects.requireNonNull(cr.getCreatedAt())))")MapStruct Version
1.7.0.Beta2
Activity
exijn commentedon Aug 20, 2026
Hi, I'd like to work on this issue.
Before implementing it, I'd like to confirm the preferred API direction. I can investigate whether this should be a new
NullValueCheckStrategyvalue, a separate null-value validation strategy, or an opt-in mapping option that generatesObjects.requireNonNull.Once the direction is confirmed, I'll add processor tests for nullable source to non-null JSpecify target mappings, verify nested and direct property mappings, and implement the smallest compatible change with documentation.