TeaVM

What is TeaVM?

TeaVM is an ahead-of-time compiler of Java bytecode. Currently, is supports translation to JavaScript and WebAssembly (experimental). It can be compared with GWT, however TeaVM does not require source code of your application and all required libraries. You can use TeaVM for building applications for the browser, due to the following features:

per-method dependency analyzer, that determines a set of methods that are really needed to run your application, so TeaVM won't translate whole JAR files;
fast JavaScript; for now it is almost as fast as the JavaScript, generated by GWT;
Java class library emulation;
integration with Maven and Eclipse;
generation of source maps;
debugger;
interoperation with JavaScript libraries together with the set of predefined browser interfaces.
supports WebAssembly output (experimental).

Quick start

There are several options of using TeaVM. One is the Maven build. The easiest way to create a new TeaVM project is to type in the command line:

mvn -DarchetypeCatalog=local \
  -DarchetypeGroupId=org.teavm \
  -DarchetypeArtifactId=teavm-maven-webapp \
  -DarchetypeVersion=0.5.0 archetype:generate

Now you can execute mvn clean package and get the generated war file. Deploy this war in Tomcat or another container, or simply unzip it and open the index.html page.

To learn TeaVM deeper, you take a look at the samples module, containing examples of TeaVM-based projects. Also you can read project's wiki.

Preview builds

You may want to access new features and don't want to wait until stable release is published on Maven Central. In this case you can get latest development build from bintray. All you need is to put the following in your pom.xml:

  <repositories>
    <repository>
      <id>teavm-dev</id>
      <url>https://dl.bintray.com/konsoletyper/teavm</url>
    </repository>
  </repositories>

IDEA plugin is also available in preview builds. You need to add corresponding repository manually to IDEA. Open Settings -> Plugins -> Browse repositories... -> Manage repositories..., click Add button and enter http://teavm.org/idea/dev/teavmRepository.xml. Then get back to Browse repositories and pick TeaVM plugin from list.

Building TeaVM

Simply clone source code (git clone https://github.com/konsoletyper/teavm.git) and run maven build (mvn clean install). You can do things a little faster (mvn clean -DskipTests) or even a little more faster (mvn clean -DskipTests -Dteavm.build.all=false).

Embedding TeaVM

If you are not satisfied with Maven, you can embed TeaVM in your program or even create your own plugin for any build tool, like Ant or Gradle. The starting point for you may be org.teavm.tooling.TeaVMTool class from teavm-tooling artifact. You may want to go deeper and use org.teavm.vm.TeaVM from teavm-core artifact, learn how TeaVMTool initializes it. To learn how to use TeaVMTool class itself, find its usages across project source code. You most likely encounter Maven and IDEA plugins.

Please, notice that these APIs for embedding are still unstable and may change between versions.

WebAssembly

WebAssembly support is in experimental status. It may lack major features available in JavaScript backend. There's no documentation yet and you should do many things by hands (like embedding generated wasm file into your page, importing JavaScript objects, etc). Look at samples/benchmark module. You should first examine pom.xml file to learn how to build wasm file from Java. Then you may want to examine index-teavm.html and index-teavm.js to learn how to embed WebAssembly into your web page.

Feedback

More information is available at the official site: http://teavm.org.

Ask your questions by email: info@teavm.org. Also you can report issues on a project's issue tracker.

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