Is there a Java library for parsing gettext PO files?

Question

Does anyone know of a Java library that will let me parse .PO files? I simply want to create a Map of IDs and Values so I can load them into a database.

Answer 1

I searched the Internet and couldn't find an existing library, either. If you use Scala, it's quite easy to write a parser yourself, thanks to its parser combinator feature.

Call PoParser.parsePo("po file content"). The result is a list of Translation.

I have made this code into a library (can be used by any JVM languages, including Java, of course!): https://github.com/ngocdaothanh/scaposer

import scala.util.parsing.combinator.JavaTokenParsers

trait Translation

case class SingularTranslation(
  msgctxto: Option[String],
  msgid:    String,
  msgstr:   String) extends Translation

case class PluralTranslation(
  msgctxto:    Option[String],
  msgid:       String,
  msgidPlural: String,
  msgstrNs:    Map[Int, String]) extends Translation

// http://www.gnu.org/software/hello/manual/gettext/PO-Files.html
object PoParser extends JavaTokenParsers {
  // Removes the first and last quote (") character of strings
  // and concats them.
  private def unquoted(quoteds: List[String]): String =
    quoteds.foldLeft("") { (acc, quoted) =>
      acc + quoted.substring(1, quoted.length - 1)
    }

  // Scala regex is single line by default
  private def comment = rep(regex("^#.*".r))

  private def msgctxt = "msgctxt" ~ rep(stringLiteral) ^^ {
    case _ ~ quoteds => unquoted(quoteds)
  }

  private def msgid = "msgid" ~ rep(stringLiteral) ^^ {
    case _ ~ quoteds => unquoted(quoteds)
  }

  private def msgidPlural = "msgid_plural" ~ rep(stringLiteral) ^^ {
    case _ ~ quoteds => unquoted(quoteds)
  }

  private def msgstr = "msgstr" ~ rep(stringLiteral) ^^ {
    case _ ~ quoteds => unquoted(quoteds)
  }

  private def msgstrN = "msgstr[" ~ wholeNumber ~ "]" ~ rep(stringLiteral) ^^ {
    case _ ~ number ~ _ ~ quoteds => (number.toInt, unquoted(quoteds))
  }

  private def singular =
    (opt(comment) ~ opt(msgctxt) ~
     opt(comment) ~ msgid ~
     opt(comment) ~ msgstr ~ opt(comment)) ^^ {
    case _ ~ ctxto ~ _ ~ id ~ _ ~ s ~ _ =>
      SingularTranslation(ctxto, id, s)
  }

  private def plural =
    (opt(comment) ~ opt(msgctxt) ~
     opt(comment) ~ msgid ~
     opt(comment) ~ msgidPlural ~
     opt(comment) ~ rep(msgstrN) ~ opt(comment)) ^^ {
    case _ ~ ctxto ~ _ ~ id ~ _ ~ idp ~ _ ~ tuple2s ~ _ =>
      PluralTranslation(ctxto, id, idp, tuple2s.toMap)
  }

  private def exp = rep(singular | plural)

  def parsePo(po: String): List[Translation] = {
    val parseRet = parseAll(exp, po)
    if (parseRet.successful) parseRet.get else Nil
  }
}