Repository files navigation

• https://github.com/decatur/j2js-compiler
• https://github.com/decatur/j2js-jre
• https://github.com/decatur/j2js-agent

2. Build all projects. An Eclipse project description is included.

3. Optionally installhttps://github.com/decatur/j2js-demos

##Building your project

It is highly recommended that you compile your project (i.e. generate class files) againstj2js-jre, and notrt.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.

##Usage

java -cp <RUNTIME_CLASSPATH> com.j2js.J2JSCompiler <basedir> <CROSS_COMPILE_CLASSPATH> <entryPointClassName> <targetLocation>

###<RUNTIME_CLASSPATH>

This is the standard Java classpath.The cross-compiler needs the project j2js-compiler, bcel and commons-io on its classpath.

###<basedir>

All non-absolute paths are relative to the basedir.

###<entryPointClassName>

The name of the class to cross-compile. This class must have a methodpublic void main(java.lang.String[]).

The compiler cross-compiles themain method and all other methods which are called from themain method.

###<CROSS_COMPILE_CLASSPATH>

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

###<targetLocation>All cross-compiled code is stored in the target location. It is one or more JavaScript file starting at0.js. Only this initial file must be included in your web page with<script src='targetLocation/0.js'/>.

###Example

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 classorg.mydomain.my-project.MyClass. Then

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.

##WarningThe projectj2js-jre contains a hand-crafted version of the Java Runtime Environment. Do not putJava/jreX/lib/rt.jar into the<CROSS_COMPILE_CLASSPATH>.

##LimitationsThe cross-compiler is able to translate any legal Java Bytecode. However, naturally, the compiler cannot support the Java Native Interface (JNI).

##Cross Compiling ScalaThe current Scala version uses JRE classes such asClassLoader orSecurityContext even in base Scala classes. These JRE classes do not make sense in a web agent context and are therefore not implemented inj2js-jre.

A workaround would be to hand-craft a subset of Scala classes, avoiding dependencies to JRE classes such asClassLoader. But this is a lot of work.

So, sadly, we cannot support Scala under this circumstance.