Details about the algorithm can be found in I. Segalovich «A fast morphological algorithm with unknown word guessing induced by a dictionary for a web search engine», MLMTA-2003.

The wrapper itself is MIT-licensed, but please remember that Yandex.MyStem is not open source and is licensed under the Yandex MyStem licensing terms.

• Java 8 or later (the artifacts are compiled with target=1.8).
• Linux, macOS, or Windows. The wrapper downloads the appropriate mystem binary the first time it is needed; you can also pass a pre-installed binary's path explicitly.

The artifact is cross-built for Scala 2.12 and Scala 2.13.

TODO: deploy recent improvements

<!-- For Scala 2.13 -->
<dependency>
    <groupId>ru.stachek66.nlp</groupId>
    <artifactId>mystem-scala_2.13</artifactId>
    <version>0.3.1</version>
</dependency>

<!-- For Scala 2.12 -->
<dependency>
    <groupId>ru.stachek66.nlp</groupId>
    <artifactId>mystem-scala_2.12</artifactId>
    <version>0.3.1</version>
</dependency>

libraryDependencies += "ru.stachek66.nlp" %% "mystem-scala" % "0.3.0"

• mystem versions 3.0 and 3.1 are supported.
• 0.3.0 modernizes the build (Scala 2.12 / 2.13 cross-build, Java 8 target, publishing via the Sonatype Central Portal) and fixes the long-standing process-leak issue (#3). See CHANGELOG below.
• Please open issues for compatibility troubles or other requests.

Important: keep one MyStem instance per mystem binary in your application. The instance owns a long-lived child process; constructing and discarding many instances will spawn many processes.

import java.io.File
import ru.stachek66.nlp.mystem.holding.{Factory, MyStem, Request}

object Example {

  // Construct once, reuse, close on shutdown.
  val mystem: MyStem =
    new Factory("-igd --eng-gr --format json --weight")
      .newMyStem("3.0", Option(new File("/path/to/mystem"))) // or None to auto-download
      .get

  def main(args: Array[String]): Unit = try {
    mystem
      .analyze(Request("Есть большие пассажиры мандариновой травы"))
      .info
      .foreach(info => println(info.initial + " -> " + info.lex))
  } finally mystem.close() // returns the OS process. Idempotent.
}

MyStem extends AutoCloseable, so you can also use it from any Using / try-with-resources style helper:

import scala.util.Using
Using.resource(new Factory().newMyStem("3.0").get) { mystem =>
  mystem.analyze(Request("Привет, мир!")).info.foreach(println)
}

A JVM shutdown hook is also installed automatically as a safety net for code paths that forget to call close().

scala.collection.JavaConversions was removed in Scala 2.13. The wrapper now exposes a Java-friendly accessor on Response, so Java callers do not need any Scala collection conversions:

import ru.stachek66.nlp.mystem.holding.Factory;
import ru.stachek66.nlp.mystem.holding.MyStem;
import ru.stachek66.nlp.mystem.holding.MyStemApplicationException;
import ru.stachek66.nlp.mystem.holding.Request;
import ru.stachek66.nlp.mystem.model.Info;
import scala.Option;

import java.io.File;
import java.util.List;

public final class MyStemJavaExample {

    private static final MyStem MYSTEM =
            new Factory("-igd --eng-gr --format json --weight")
                    .newMyStem("3.0", Option.<File>empty())
                    .get();

    public static void main(String[] args) throws MyStemApplicationException {
        try {
            List<Info> result =
                    MYSTEM.analyze(Request.apply("И вырвал грешный мой язык")).getInfoAsList();

            for (Info info : result) {
                System.out.println(info.initial() + " -> " + info.lex() + " | " + info.rawResponse());
            }
        } finally {
            MYSTEM.close();
        }
    }
}

MYSTEM.close() is also safe to call as the body of a try-with-resources since MyStem implements java.lang.AutoCloseable.

• GrammarInfo.person (API change). The 1p / 2p / 3p person tags emitted by mystem are now populated into a new person: Set[Person.Value] field. Previously the parser silently dropped them on the floor. Note: positional constructor calls to GrammarInfo will break — named-argument call sites are unaffected.
• Parens-pipe gr parsing. Real mystem 3.x output with --weight emits multi-analysis strings like A,plen=(acc,sg,m,anim|gen,sg,m|gen,sg,n). The pre-existing parser threw NoSuchElementException on the leading (. New GrammarInfoParsing.toGrammarInfos(s): List[GrammarInfo] returns one GrammarInfo per pipe-alternative; the previous toGrammarInfo remains and now returns the most-likely interpretation (mystem orders alternatives by descending probability, so .head).
• Wire-format aliases. mystem 3.x emits indic (we declared Value("ind") for indicative mood) and praet (we declared Value("past") for past tense). Without alias support every real verb output threw on parsing. GrammarMapBuilder.aliases (public) now maps indic→ind and praet→past; both forms parse.
• Process robustness. ExternalProcessServer.syncRequest no longer spins forever in while (!reader.ready()) {} when the child process exits without responding — BufferedReader.ready() returns false at EOF, not true. The busy-wait now also gates on process.isAlive, the drain loop breaks on null (avoiding appending the literal string "null"), and an exit-without-output surfaces as IOException("process exited before producing any response") so FailSafeExternalProcessServer can spawn a fresh child rather than wrap an empty success. The restart-on-death path is now functionally testable.
• Refactor: Factory.getExecutable's cached-binary version check is extracted into private[holding] isCorrectVersion(file, version): Boolean. Same observable contract, but the version-matching logic is now exercisable in unit tests without hitting the CDN.
• Test coverage. ~70 new tests (75 → 140 across 15 test classes). Statement coverage > 80%, branch coverage > 74% under scoverage. Direct unit tests for syncRequest (using python3 -u as a portable line-buffered echo stand-in), isCorrectVersion, MyStem.normalize, MyStemApplicationException, archive edge cases (empty archive, directory-as-first-entry), FailSafeExternalProcessServer restart-on-death, plus broader coverage of GrammarInfoParsing (parens-pipe alternatives, person, alias support, fail-loud on unknown tags inside parens).

• Fixed process leak (#3): MyStem now extends AutoCloseable; an internal JVM shutdown hook destroys the spawned mystem process if the user forgets to call close(). This unblocks Maven Surefire / mvn package runs that previously hung on Windows.
• Java-friendly API: Response#getInfoAsList(): java.util.List<Info> replaces the need for the (removed) scala.collection.JavaConversions.
• Cross-built for Scala 2.12 + 2.13 with profiles scala-2.12 / scala-2.13.
• Java 8 target preserved; runs on JDK 8/11/17 (CI matrix).
• Modernized build: publishing via Sonatype Central Portal (OSSRH was sunset 2025-06-30); current commons-compress, slf4j, org.json, scalatest, scala-maven-plugin.
• logback-classic is now a test dependency; consumers pick their own logging backend (only slf4j-api is on the compile classpath).
• OS detection fixed for modern Windows (10/11) — used to misroute to the macOS download URL.
• Traversable → Iterable throughout (deprecated/removed in 2.13/3).
• Linting + formatting: scalafmt, strict scalac flags (-deprecation -feature -unchecked -Xlint:_).
• GitHub Actions CI with a Java × Scala matrix and scoverage report.

See git log and the release page.

@misc{alekseev2018mystemscala,
    author = {Anton Alekseev},
    title = {mystem-scala},
    year = {2018},
    publisher = {GitHub},
    journal = {GitHub repository},
    howpublished = {\url{https://github.com/alexeyev/mystem-scala/}},
    commit = {the latest commit of the codebase you have used}
}

If you cite the wrapper, please also cite the original algorithm's paper.

Anton Alekseev anton.m.alexeyev@gmail.com

• Vladislav Dolbilov, @darl
• Mikhail Malchevsky
• @anton-shirikov
• Filipp Malkovsky
• @dizzy7

• https://yandex.ru/dev/mystem/
• https://nlpub.ru/Mystem
• https://github.com/Digsolab/pymystem3