how to create custom key and custom value in MapReduce Job

[DataFlair Team]

I want to send more than one value from Mapper to reducer, I can do the same by creating custom key / value. How to create custom key and value ?

[DataFlair Team]

In Hadoop, data types to be used as the key must implement WritableComparable interface and data types to be used as value must implement Writable interface.
If your custom key/value are of the same type then you can write one custom datatype for both the key/value which implements WritableComparable otherwise you need to implement two different data types. One for the key which implements the WritableComparable interface and other for value which implements Writable interface.

//Custom Data-Type
public class MyCustomeKey implements WritableComparable
{}

//Create Mapper with Custome Key
public class MyMapper extends Mapper
{
}

For more details, please follow:
http://data-flair.training/blogs/hadoop-mapreduce-introduction-tutorial-comprehensive-guide/

[Author]

Posts