Live instructor-led & Self-paced Online Certification Training Courses (Big Data, Hadoop, Spark) Forums Hadoop how to create custom key and custom value in MapReduce Job

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  • #4682

    dfbdteam3
    Moderator

    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 ?

    #4683

    dfbdteam3
    Moderator

    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/

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