I have written the code to access the Hive table using SparkSQL. Here is the code:
SparkSession spark = SparkSession
.builder()
.appName("Java Spark Hive Example")
.master("local[*]")
.config("hive.metastore.uris", "thrift://localhost:9083")
.enableHiveSupport()
.getOrCreate();
Dataset<Row> df = spark.sql("select survey_response_value from health").toDF();
df.show();
I would like to know how I can convert the complete output to String or String array? As I am trying to work with another module where only I can pass String or String type Array values.
I have tried other methods like .toString
or typecast to String values. But did not worked for me.
Kindly let me know how I can convert the DataSet values to String?
Here is the sample code in Java.
public class SparkSample {
public static void main(String[] args) {
SparkSession spark = SparkSession
.builder()
.appName("SparkSample")
.master("local[*]")
.getOrCreate();
//create df
List<String> myList = Arrays.asList("one", "two", "three", "four", "five");
Dataset<Row> df = spark.createDataset(myList, Encoders.STRING()).toDF();
df.show();
//using df.as
List<String> listOne = df.as(Encoders.STRING()).collectAsList();
System.out.println(listOne);
//using df.map
List<String> listTwo = df.map(row -> row.mkString(), Encoders.STRING()).collectAsList();
System.out.println(listTwo);
}
}
"row" is java 8 lambda parameter. Please check developer.com/java/start-using-java-lambda-expressions.html