Expected behavior

MapStruct generates a null-check that considers only non-primitive method parameters. When all non-primitive arguments are null, the generated mapper method returns null early, even if primitive parameters contain valid values.

As a result, mappings for primitive (or boxed-with-default) arguments are skipped entirely.

Expected behavior

If primitive parameters (e.g. int, boolean) have valid values, MapStruct should still map them to the target object, even when all non-primitive parameters are null.

At minimum, primitive arguments should not be ignored solely because non-primitive arguments are null.

Actual behavior

MapStruct generates an early return null when all non-primitive parameters are null, causing primitive argument mappings to be ignored.

Example

Mapper method:

Target map(
    String sku,
    String name,
    Long categoryId,
    int size,
    int pageNumber,
    boolean draft
);

Generated logic (simplified):

if (sku == null && name == null && categoryId == null) {
    return null;
}

target.setSize(size);
target.setPageNumber(pageNumber);
target.setDraft(draft);

In this case:

• sku, name, and categoryId are null
• size, pageNumber, and draft have valid values

However, the method returns null, and primitive fields are never mapped.

Impact

• This behavior makes it impossible to create partially populated target objects when:
• all reference-type parameters are null
• primitive parameters still carry meaningful values (e.g. pagination, flags)
• This is especially problematic for search/filter DTOs.

Workaround

• Convert primitive parameters to wrapper types (Integer, Boolean)
• Or manually implement mapping logic instead of relying on generated code

Actual behavior

No response

Steps to reproduce the problem

I have told in description

MapStruct Version

1.6.3