Java Processor to generate Typescript Definition file (.d.ts) from whatever Java classes.

---
title: Java to TypeScript Conversion Process
---
flowchart LR

    subgraph "Java Compiler"
        B(Java2TypeScript Processor) 
    end
   
    subgraph "Java Project"
        direction LR
        A[Package_Info.java]:::javaSrc ---|Lookup annotations| B
        C[Dependencies Classpath]:::javaSrc ---|Lookup classes| B
    end

    subgraph "Typescript"
        D[<Output>.d.ts]:::tsFile
        E[<Output>_types.ts]:::tsFile
    end
    
    B o-->|Generate| D
    B o-->|Generate| E
    

This is to help developing on JVM javascript engine, either GraalJs or Rhino using Typescript

Nashorn has been DEPRECATED (refer to JEP335 )

The main goal is having the definitions available in the modern IDE like Visual Studio Code and Atom and then use the intellisense feature available for java classes within typescript

It is not a transpiler from Java to Javascript like datathings/java2typescript

• typescript-generator

typescript-generator is a tool for generating TypeScript definition files (.d.ts) from Java JSON classes. If you have REST service written in Java using object to JSON mapping you can use typescript-generator to generate TypeScript interfaces from Java classes.

• 1c

1c is aimed to compile TypeScript to runnable code on both JVM and web browser. You can implement the full stack with TypeScript while using libraries from Maven and NPM together.

• Rhino is compliant with CommonJS module loader for the JVM

Graaljs is compliant with ES6 module loader for the JVM

To give an idea about how to work there is a demo available online here.

The backend of such demo has been developed using typescript on jvm provided by this project itself (dogfooding). java2typescript-demo project

Basic idea is to develop a Project by mixing Java & Javascript code (or completely in Javascript) relying on the Nashorn Javascript engine or Rhino javascript engine. This powerful engines enable Javascript language in JVM and they allow to access to every java class present in classpath in a pretty straightforward way. That's cool, the Javascript is very easy to learn, but the question are :

1. Is it possible develop a complete and well structured Javascript application ?
2. Developing in Javascript on JVM is as productive as programming in Java ?

Just to answer the questions above that this project has been developed.

1. Is it possible develop a complete and well structured Javascript application ?

Yes it is, but with help of a powerful Typescript that fills language's gaps and produce Javascript as output

1. Developing in Javascript on JVM is as productive as programming in Java ?

Yes it could be, but we need :

• An IDE with intellisense capability that is able to inspect java/javascript classes during development.

This is the main goal of project, that is to generate Typescript Declarations enabling every Typescript-Aware IDE (eg. Atom, VSCode) to give you the intellisense feature make more comfortable use access to Java features/classes from Javascript

• A module module system that allow to arrange application in separate well-defined modules

This is achieved by project jvm-npm that enable use of commonJS enabling Typescript Modules.

Let assume that you have successfully setup a java project

Create a file package-info.java and annotate the given package with @Java2TS that will contain all the @Type of which you want the Typescript declaration.

** Type Attributes **

Example

@Java2TS(declare = {

  @Type(java.nio.file.Files.class, export="true"),
  @Type(java.nio.file.Path.class),
  @Type(java.nio.file.Paths.class, export="true"),

  @Type(value=java.util.stream.Stream.class,export=true),

  @Type(java.util.Collection.class),
  @Type(java.util.Map.class),
  @Type(value=java.util.List.class, alias="List" ),
  @Type(java.util.Set.class),
  @Type(value=java.util.Arrays.class, export=true),

  @Type(java.util.Optional.class),

  @Type(value=java.net.URI.class, export=true),
  @Type(java.net.URL.class),

  @Type(java.lang.Runnable.class, functional=true)

})
package org.mypackage;

<dependency>
  <groupId>org.bsc.processor</groupId>
  <artifactId>java2ts-processor</artifactId>
  <version>version</version>
</dependency>

Graajs compatibility see samples

<plugin>
  <groupId>org.bsc.maven</groupId>
  <artifactId>maven-processor-plugin</artifactId>
  <version>5.1</version>
  <executions>
    <execution>
      <id>process</id>
      <goals>
        <goal>process</goal>
      </goals>
      <phase>generate-sources</phase>
      <configuration>
          <outputDirectory>${project.build.directory}</outputDirectory>
       <options>
            <ts.outfile>name</ts.outfile><!-- name of generated file -->
       </options>
      </configuration>
    </execution>
  </executions>
</plugin>

Enforce Rhino compatibility see samples

<plugin>
  <groupId>org.bsc.maven</groupId>
  <artifactId>maven-processor-plugin</artifactId>
  <version>5.1</version>
  <executions>
    <execution>
      <id>process</id>
      <goals>
        <goal>process</goal>
      </goals>
      <phase>generate-sources</phase>
      <configuration>
          <outputDirectory>${project.build.directory}</outputDirectory>
       <options>
            <ts.outfile>name</ts.outfile><!-- name of generated file -->
            <compatibility>rhino</compatibility>
       </options>
      </configuration>
    </execution>
  </executions>
</plugin>

The easier way to start your Typescript on JVM project is using the provided maven archetype

Interactive Mode

mvn archetype:generate \
-DarchetypeGroupId=org.bsc.processor \
-DarchetypeArtifactId=java2ts-processor-archetype \
-DarchetypeVersion=1.1.0