org.apache.flink.api.java.functions

Class NullByteKeySelector<T>

java.lang.Object

org.apache.flink.api.java.functions.NullByteKeySelector<T>

Type Parameters:

T - The type of the input element.

All Implemented Interfaces:

Serializable, Function, KeySelector<T,Byte>

@Internal
public class NullByteKeySelector<T>
extends Object
implements KeySelector<T,Byte>

Used as a dummy KeySelector to allow using keyed operators for non-keyed use cases. Essentially, it gives all incoming records the same key, which is a (byte) 0 value.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
NullByteKeySelector()

Method Summary

Modifier and Type	Method and Description
Byte	getKey(T 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

Constructor Detail

NullByteKeySelector

public NullByteKeySelector()

Method Detail

getKey

public Byte getKey(T 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<T,Byte>

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.