StringKpaPrimitive

Abstract base class for KpaPrimitive implementations that always represent a plain string value.

All type predicates except isString are hard-wired to false; all non-string accessors return null. Subclasses need only provide content — the string to expose — and KpaPrimitive is fully implemented.

Typical use: adapter-specific leaf nodes that carry only a string payload (attribute values, text nodes, CSV cells, etc.) extend this class and override content to return the appropriate string.