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Build a Polyglot Native Executable (Java and JavaScript)

With the GraalVM Polyglot API you can embed and run code from a guest language in a Java-based host application. GraalVM makes it possible to compile a Java application ahead-of-time with embedded JavaScript and to create a polyglot native executable. See the Embedding Languages documentation for more information about how a Java host application can interact with a guest language like JavaScript.

Note: JavaScript support by GraalVM Native Image is considered general availability.

This guide demonstrates how to build a polyglot native executable with Java as a host language and JavaScript as a guest language.

For the demo part, you will use a simple JSON Pretty Printer Java application that prints the output in JSON format:

import java.io.*;
import java.util.stream.*;
import org.graalvm.polyglot.*;

public class PrettyPrintJSON {
  public static void main(String[] args) throws java.io.IOException {
    BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
    String input = reader.lines()
    .collect(Collectors.joining(System.lineSeparator()));
    try (Context context = Context.create("js")) {
      Value parse = context.eval("js", "JSON.parse");
      Value stringify = context.eval("js", "JSON.stringify");
      Value result = stringify.execute(parse.execute(input), null, 2);
      System.out.println(result.asString());
    }
  }
}

Prerequisite

Make sure you have installed a GraalVM JDK. The easiest way to get started is with SDKMAN!. For other installation options, visit the Downloads section.

Download or clone the demos repository and navigate to the directory native-image/build-with-js-embedded/:

 git clone https://github.com/graalvm/graalvm-demos

 cd graalvm-demos/native-image/build-with-js-embedded

Open the project configuration file (in this case, pom.xml) and examine the required dependencies to enable interoperability with JavaScript.

To enable the polyglot runtime:

<dependency>
    <groupId>org.graalvm.polyglot</groupId>
    <artifactId>polyglot</artifactId> 
    <version>${graalvm.polyglot.version}</version>
</dependency>

To enable Javascript:

<dependency>
    <groupId>org.graalvm.polyglot</groupId>
    <artifactId>js</artifactId> 
    <version>${graalvm.polyglot.version}</version>
</dependency>

Compile and package the project with Maven:
```
 mvn clean package
```
Build a native executable:
```
 mvn -Pnative package
```
It takes several minutes as it does not just build the executable, but also pulls in the JavaScript engine. The JavaScript context will be available in the generated image.

Note: Building a polyglot native executable requires more physical memory because the Truffle framework is included.

Run the resulting executable and perform some pretty-printing:

 ./target/PrettyPrintJSON <<EOF
 {"GraalVM":{"description":"Language Abstraction Platform","supports":["combining languages","embedding languages","creating native images"],"languages": ["Java", "JavaScript", "Python"]}}
 EOF

The expected output is:

 {
 "GraalVM": {
     "description": "Language Abstraction Platform",
     "supports": [
       "combining languages",
       "embedding languages",
       "creating native images"
     ],
     "languages": [
       "Java",
       "JavaScript",
       "Python"
     ]
   }
 }

Build a Polyglot Native Executable (Java and JavaScript)

Prerequisite

Related Documentation

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