Scala dynamic String interpolation - Read from properties file

Question

I tried to get the log message from message.properties and did string interpolation with that log message.In this time,The log message is not interpolated with original message.

I am not able to get string interpolated result and am getting the output as log message what i have specified in properties file

Here I dont want to hard code any log message in scala file,Instead of this,I want to get all message from properties file and redirected into application log after interpolating string value.

import com.typesafe.config.ConfigFactory
import grizzled.slf4j.Logging
object Test extends Logging {
  def main(args: Array[String]){
    val subjectArea="Member"
    val  messageProp = ConfigFactory.load("message.properties")
    val log=messageProp.getString("log.subject.area")
    debug(s"$log")
  }
}

message.properties
log.subject.area=The Subject Area : $subjectArea

Console Output: The Subject Area : $subjectArea i want this output : The Subject Area : Member

Thanks in advance!!! Test.scala message.propeties

What is the question?

Jerome Reinländer
– Jerome Reinländer

2017-11-16 12:35:28 +00:00
Commented Nov 16, 2017 at 12:35 — Jerome Reinländer
– Jerome Reinländer, Commented Nov 16, 2017 at 12:35

tkroman · Accepted Answer · 2017-11-16 12:44:31Z

1

This is not a string interpolation problem. You want a lightweight templating engine (e.g. http://jtwig.org/documentation/quick-start/application or something else). I feel that most of them would be an overkill if your problem is as simple as in the snippet you've provided.

If you want to do something more or less complex, then sure, go with template engines.

Otherwise, I'd just go with string substitution.

answered Nov 16, 2017 at 12:44

tkroman

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Dima · Accepted Answer · 2017-11-16 13:20:45Z

0

String interpolation only works with constants. To do what you want dynamically, you need to write some explicit processing yoruself (or use a template engine library). Something like this, perhaps?

 val substPattern = """\$\{(.+?)\}""".r
 import java.util.regex.Matcher.{ quoteReplacement => qq }
 def processSubstitutions(
   input: String, 
   vars: Map[String, String]
 ) = substPattern.replaceAllIn(
     input, { m => 
       val ref = m.group(1)
       qq(vars.getOrElse(ref, ref)
     }
 )

 val vars = Map("subjectArea" -> "Member")
 val  messageProp = ConfigFactory.load("message.properties")
 val log=processSubstitutions(
    messageProp.getString("log.subject.area"),
    vars
 )

answered Nov 16, 2017 at 13:20

Dima

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