Read values from config in Scala

Question

In Scala, if I have the following config:

id = 777
username = stephan
password = DG#%T@RH

The idea is to open a file, transform it into a string, do getLineson it and get the right-hand side value based on the left-hand side key. What would be the nicest code to read constant configuration values into my app?

Client usage: val username = config.get("username")

Answer 1

Best way would be to use a .conf file and the ConfigFactory instead of having to do all the file parsing by yourself:

import java.io.File
import com.typesafe.config.{ Config, ConfigFactory }

// this can be set into the JVM environment variables, you can easily find it on google
val configPath = System.getProperty("config.path")

val config = ConfigFactory.parseFile(new File(configPath + "myFile.conf"))

config.getString("username")

I usually use scalaz Validation for the parseFile operation in case the file it's not there, but you can simply use a try/catch if you don't know how to use that.

Answer 2

You can configure this values in json file ( I have named it as config.json)as below

{
  "id": "777",
  "username": "stephan",
  "password": "DG#%T@RH"
}

Now you can store this json file at hdfs location and read this file from hdfs location using spark in your scala and read your configuration values as below:

val configData = spark.read.option("multiline",true).json("/tmp/user/config.json")
val id = configData.select("id").collect()(0)  
val username = configData.select("username").collect()(0)  
val password = configData.select("password").collect()(0)

In the first line of the code you need to use option with parameter of multiline = true as your json file will have each value on new line. if you don't use that you will get error saying _corrupt_record : string

Answer 3

If your Spark version is less than 2.2 then first convert your JSON file content in to JSON String i.e. convert your file content to single string and load it to HDFS location.

Sample JSON:

{ 
  "planet" : "Earth",
  "continent" : "Antarctica"
}

Convert to:

{ "planet" : "Earth", "continent" : "Antarctica"}

Next, to access data create a data frame:

val dataDF = spark.read.format("json").load("<HDFS location>")
val planet = dataDF.select("planet").collect(0).mkString("")

Hope this helps Spark 2.1 and less users.