Load CSV data in to Dataframe and convert to Array using Apache Spark (Java)

问题

I have a CSV file with below data :

1,2,5  
2,4  
2,3 

I want to load them into a Dataframe having schema of string of array

The output should be like below.

[1, 2, 5]  
[2, 4]  
[2, 3] 

This has been answered using scala here: Spark: Convert column of string to an array

I want to make it happen in Java.
Please help

回答1:

Below is the sample code in Java. You need to read your file using spark.read().text(String path) method and then call the split function.

import static org.apache.spark.sql.functions.split;

public class SparkSample {
    public static void main(String[] args) {
        SparkSession spark = SparkSession
                .builder()
                .appName("SparkSample")
                .master("local[*]")
                .getOrCreate();
        //Read file
        Dataset<Row> ds = spark.read().text("c://tmp//sample.csv").toDF("value");
        ds.show(false);     
        Dataset<Row> ds1 = ds.select(split(ds.col("value"), ",")).toDF("new_value");
        ds1.show(false);
        ds1.printSchema();
    }
}

回答2:

you can use VectorAssembler class to create as array of features, which is particulary useful with pipelines:

val assembler = new VectorAssembler()
  .setInputCols(Array("city", "status", "vendor"))
  .setOutputCol("features")

https://spark.apache.org/docs/2.2.0/ml-features.html#vectorassembler

来源：https://stackoverflow.com/questions/47687194/load-csv-data-in-to-dataframe-and-convert-to-array-using-apache-spark-java