You need to install this and the following projects
Build all projects. An Eclipse project description is included.
Optionally install https://github.com/decatur/j2js-demos
Building your project
It is highly recommended that you compile your project (i.e. generate class files) against
j2js-jre, and not
rt.jar. This way you avoid link errors (missing classes or methods) at the cross-compile stage. See the warning at the bottom of the document.
java -cp <RUNTIME_CLASSPATH> com.j2js.J2JSCompiler <basedir> <CROSS_COMPILE_CLASSPATH> <entryPointClassName> <targetLocation>
This is the standard Java classpath. The cross-compiler needs the project j2js-compiler, bcel and commons-io on its classpath.
All non-absolute paths are relative to the basedir.
The name of the class to cross-compile. This class must have a method
public void main(java.lang.String).
The compiler cross-compiles the
main method and all other methods which are called from the
This classpath must contain all classes whose methods are referenced by the main method. In normal operation, this classpath consists of
- the j2js-jre classes directory or jar
- the j2js-agent classes directory or jar
- the classes directory of your personal project
0.js. Only this initial file must be included in your web page with
Suppose the directory layout is
|- j2js-compiler |- j2js-jre |- j2js-agent |- my-project |- target |- assemblies |- 0.js |- 1.js |- 2.js ...
and you want to cross-compile class
java -cp ../j2js-compiler/libs/commons-io-1.4.jar;^ ../j2js-compiler/libs/bcel-5.1.jar;^ ../j2js-compiler/target/classes ^ com.j2js.J2JSCompiler . ^ target/classes;../j2js-jre/target/classes;../j2js-agent/target/classes ^ org.mydomain.my-project.MyClass target/assemblies
will create the assemblies.
j2js-jre contains a hand-crafted version of the Java Runtime Environment. Do not put
Java/jreX/lib/rt.jar into the
The cross-compiler is able to translate any legal Java Bytecode. However, naturally, the compiler cannot support the Java Native Interface (JNI).
Cross Compiling Scala
The current Scala version uses JRE classes such as
SecurityContext even in base Scala classes. These JRE classes do not make sense in a web agent context and are therefore not implemented in
A workaround would be to hand-craft a subset of Scala classes, avoiding dependencies to JRE classes such as
ClassLoader. But this is a lot of work.
So, sadly, we cannot support Scala under this circumstance.