org.apache.flink.streaming.util.keys

Class KeySelectorUtil.OneKeySelector<IN,K>

java.lang.Object

org.apache.flink.streaming.util.keys.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 Summary

Modifier and Type	Method and Description
K	getKey(IN value) User-defined function that deterministically extracts the key from an object.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

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.