Package org.apache.flink.streaming.util.keys

Class KeySelectorUtil.OneKeySelector<IN,​K>

  • Type Parameters:
    IN - The type of the elements where the key is extracted from.
    K - The type of the key.
    All Implemented Interfaces:
    Serializable, Function, KeySelector<IN,​K>
    Enclosing class:
    KeySelectorUtil
    public static final class KeySelectorUtil.OneKeySelector<IN,​K>
extends Object
implements KeySelector<IN,​K>
    Key extractor that extracts a single field via a generic comparator.
    See Also:
    Serialized Form

    • Method Detail

      • getKey

        public K getKey​(IN value)
         throws Exception
        Description copied from interface: KeySelector
        User-defined function that deterministically extracts the key from an object.

        For example for a class: 

                public class Word {
                String word;
                int count;
        }

        The key extractor could return the word as a key to group all Word objects by the String they contain.

        The code would look like this 

                public String getKey(Word w) {
                return w.word;
        }
        Specified by:
        getKey in interface KeySelector<IN,​K>
        Parameters:
        value - The object to get the key from.
        Returns:
        The extracted key.
        Throws:
        Exception - Throwing an exception will cause the execution of the respective task to fail, and trigger recovery or cancellation of the program.