Starting Hive-Client Programmatically With Scala


Hive defines a simple SQL-like query language to querying and managing large datasets called Hive-QL ( HQL ). It’s easy to use if you’re familiar with SQL Language. Hive allows programmers who are familiar with the language to write the custom MapReduce framework to perform more sophisticated analysis.

In this Blog,we will learn how to create a hive client with scala to execute basic hql commands,first create a scala project with scala 2.12 version

now add following properties in your build.sbt file

name := "hive_cli_client"

version := "1.0"

scalaVersion := "2.12.2"

libraryDependencies += "org.apache.hive" % "hive-exec" % "1.2.1" excludeAll
                       ExclusionRule(organization = "org.pentaho")

libraryDependencies += "org.apache.hadoop" % "hadoop-common" % "2.7.3"

libraryDependencies += "org.apache.httpcomponents" % "httpclient" % "4.3.4"

libraryDependencies += "org.apache.hadoop" % "hadoop-client" % "2.6.0"

libraryDependencies += "org.apache.hive" % "hive-service" % "1.2.1"

libraryDependencies += "org.apache.hive" % "hive-cli" % "1.2.1"

libraryDependencies += "org.scalatest" % "scalatest_2.12" % "3.0.3"

in my case i am using hive 2.1.1,you can use any,let the dependencies to be resolved,now add a scala class in your project named as hiveclient

package cli

import java.io.IOException

import scala.util.Try

import org.apache.hadoop.hive.cli.CliSessionState
import org.apache.hadoop.hive.conf.HiveConf
import org.apache.hadoop.hive.ql.Driver
import org.apache.hadoop.hive.ql.session.SessionState

/**
 * Hive meta API client for Testing Purpose
 *
 * @author Anubhav
 */
class HiveClient {

  val hiveConf = new HiveConf(classOf[HiveClient])

  /**
   * Get the hive ql driver to execute ddl or dml
   *
   * @return
   */
  private def getDriver: Driver = {
    val driver = new Driver(hiveConf)
    SessionState.start(new CliSessionState(hiveConf))
    driver
  }

  /**
   * @param hql
   * @throws org.apache.hadoop.hive.ql.CommandNeedRetryException
   * @return int
   */

  def executeHQL(hql: String): Int = {
    val responseOpt = Try(getDriver.run(hql)).toEither
    val response = responseOpt match {
      case Right(response) => response
      case Left(exception) => throw new Exception(s"${ exception.getMessage }")
    }
    val responseCode = response.getResponseCode
    if (responseCode != 0) {
      val err: String = response.getErrorMessage
      throw new IOException("Failed to execute hql [" + hql + "], error message is: " + err)
    }
    responseCode
  }

}

it has one public method executeHQL that called private method getDriver to get the hiveDriver instance and execute hql with it,this method will give back the response code back

now write the test case to test this hive client

import cli.HiveClient
import org.scalatest.FunSuite

class HiveClientTest extends FunSuite {

  val hiveClient = new HiveClient

  test("testing for the hql query") {
    assert(hiveClient.executeHQL("DROP TABLE IF EXISTS DEMO") == 0)
    assert(hiveClient.executeHQL("CREATE TABLE IF NOT EXISTS DEMO(id int)") == 0)
    assert(hiveClient.executeHQL("INSERT INTO DEMO VALUES(1)") == 0)
    assert(hiveClient.executeHQL("SELECT * FROM DEMO") == 0)
    assert(hiveClient.executeHQL("SELECT COUNT(*) FROM DEMO") == 0)

  }

}

now run these  test cases ooo.png

i hope this blog will be helpful happy coding

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