public interface KeyValueMapper<K,V,VR>

The KeyValueMapper interface for mapping a key-value pair to a new value of arbitrary type. For example, it can be used to

• map from an input KeyValue pair to an output KeyValue pair with different key and/or value type (for this case output type VR == KeyValue<NewKeyType,NewValueType>)
• map from an input record to a new key (with arbitrary key type as specified by VR)

This is a stateless record-by-record operation, i.e, apply(Object, Object) is invoked individually for each record of a stream (cf. Transformer for stateful record transformation). KeyValueMapper is a generalization of ValueMapper.