java2script

Quick Start

Installation

see https://github.com/BobHanson/java2script/tree/master/sources/net.sf.j2s.core/dist for installation instructions.

The instructions given here are for a much earlier version.

Prerequisites

• Eclipse Neon (4.6) or higher.

(Java2Script has been successfully tested in Eclipse Neon and Oxygen on Mac and Windows platforms. No reason to believe it would not also work for Linux; just haven’t tried that recently.)

Install the Java2Script transpiler Eclipse plug-in

Step 1: Click [here] to download the Java2Script transpiler Eclipse plugin net.sf.j2s.core.jar.

(The Eclipse plugin net.sf.j2s.core.jar contains the Java-to-Java2Script transpiler. When Eclipse compiles Java code with this plugin installed it will create .js files that match the standard .class files normally created by the Java compiler.)

Step 2: Move the plugin net.sf.j2s.core.jar into your Eclipse dropins directory.

For Mac OSX: The Eclipse dropins directory is /Applications/Eclipse.app/Contents/Eclipse/dropins. This directory is not visible by default. To open it select the Finder menu item Go > Go to Folder [Shift-Cmd G], enter /Applications/Eclipse.app/Contents/Eclipse/dropins and click the Go button.

Step 3: Restart Eclipse

Step 4: Check if the plugin net.sf.j2s.core.jar was successfully installed.

• Select the Eclipse menu item Eclipse > About Eclipse
• Click the Installation Details button
• Select the Plug-ins tab (Wait several seconds until the table is filled.)
• Type j2s into the search field at the top.

You should now see the plugin Java2Script Core listed in the table.

If you can’t find it please check if you moved net.sf.j2s.core.jar into the proper directory. Also make sure that you restarted Eclipse.

Create a Java2Script (J2S) Project

Create an Eclipse Java project for your work, if you have not done so already.

Make sure your source code is a source directory of the project (by default: src/).

If you want to check or edit the source directories of the project, select the Eclipse menu item Project > Properties, click Java Build Path and select the Source tab.

All code must be available as Java source code. Therefore your project must not include any dependencies to Jar files. However you may include source code generated from decompiling .class files.

Java 9 and 10 are currently not supported. Java 8 works fine.

Install the JavaScript version of the Java Runtime Environment

Step 1: Click [here] to download the the JavaScript version of the Java Runtime Environment as a ZIP file.

Step 2: Unzip the ZIP file into your project directory and rename the created directory to site.

All JavaScript code produced by the transpiler will be in the project’s site directory.

Enable the Java2Script transpiler

Step 1: In your project directory create a file .j2s with the content:

j2s.compiler.status=enable

Step 2: Make the project use the Java2Script transpiler rather than the standard Java compiler

• Edit the file .project your project directory
• Change the name of the buildSpec/buildCommand from org.eclipse.jdt.core.javabuilder to net.sf.j2s.core.java2scriptbuilder.

Build the Project

Build your project as you normally would. Java class files will be created as usual in the bin directory. JavaScript equivalents of these files will be created in the site/swingjs/j2s directory. You might have to do a project refresh to see these site files.

Test the JavaScript version of your project

The J2S transpiler will automatically set up for you in the site directory a sample HTML page for any class that subclasses JApplet or contains a public void main(String[] args) method. You will want to associate those files with an external HTML browser. We recommend Firefox.

Since you will be running AJAX locally within these browsers, you may need to enable local file reading in your browser. Instructions for doing that can be found at http://wiki.jmol.org/index.php/Troubleshooting/Local_Files.

Add more Java classes

If you find you are missing a standard Java Runtime library class, please contact Bob Hanson at mailto:hansonr@stolaf.edu. You can try adding these yourself by temporarily adding one or more of the Java classes found at http://grepcode.com to the proper package in your project. For example, java/awt.

If you do that, be sure to use the OpenJDK version. Most of the current code in the Java2Script project started with Java 6-b14 or 6-b27. Build your project, then delete these Java files, because you do not necessarily want your Java code using that version, just JavaScript.

Contribute to Java2Script

Developers who like to contribute to the Java2Script project, i.e. like to work on the Java-to-JavaScript transpiler or the Java runtime environment code should have a look at “Contribution…”.

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