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95 lines
3.3 KiB
Markdown
95 lines
3.3 KiB
Markdown
⚠️ Deprecated. Consider to adopt the TypeScript eco system.
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A lightweight component to expose computational MATLAB resources over HTTP.
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#j2js-compiler
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A Java Bytecode to JavaScript Cross-Compiler.
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##Installation
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1. You need to install this and the following projects
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* https://github.com/decatur/j2js-compiler
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* https://github.com/decatur/j2js-jre
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* https://github.com/decatur/j2js-agent
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2. Build all projects. An Eclipse project description is included.
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3. Optionally install https://github.com/decatur/j2js-demos
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##Building your project
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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.
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##Usage
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java -cp <RUNTIME_CLASSPATH> com.j2js.J2JSCompiler <basedir> <CROSS_COMPILE_CLASSPATH> <entryPointClassName> <targetLocation>
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###`<RUNTIME_CLASSPATH>`
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This is the standard Java classpath.
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The cross-compiler needs the project j2js-compiler, bcel and commons-io on its classpath.
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###`<basedir>`
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All non-absolute paths are relative to the basedir.
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###`<entryPointClassName>`
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The name of the class to cross-compile. This class must have a method
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`public void main(java.lang.String[])`.
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The compiler cross-compiles the `main` method and all other methods which are called from the `main` method.
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###`<CROSS_COMPILE_CLASSPATH>`
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This classpath must contain all classes whose methods are referenced by the main method.
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In normal operation, this classpath consists of
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* the j2js-jre classes directory or jar
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* the j2js-agent classes directory or jar
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* the classes directory of your personal project
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###`<targetLocation>`
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All cross-compiled code is stored in the target location. It is one or more JavaScript file starting at
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`0.js`. Only this initial file must be included in your web page with
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`<script src='targetLocation/0.js'/>`.
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###Example
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Suppose the directory layout is
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|- j2js-compiler
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|- j2js-jre
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|- j2js-agent
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|- my-project
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|- target
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|- assemblies
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|- 0.js
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|- 1.js
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|- 2.js ...
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and you want to cross-compile class `org.mydomain.my-project.MyClass`. Then
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java -cp ../j2js-compiler/libs/commons-io-1.4.jar;^
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../j2js-compiler/libs/bcel-5.1.jar;^
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../j2js-compiler/target/classes ^
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com.j2js.J2JSCompiler . ^
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target/classes;../j2js-jre/target/classes;../j2js-agent/target/classes ^
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org.mydomain.my-project.MyClass target/assemblies
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will create the assemblies.
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##Warning
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The project `j2js-jre` contains a hand-crafted version of the Java Runtime Environment. Do not put `Java/jreX/lib/rt.jar` into the `<CROSS_COMPILE_CLASSPATH>`.
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##Limitations
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The cross-compiler is able to translate any legal Java Bytecode. However, naturally, the compiler cannot support the Java Native Interface (JNI).
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##Cross Compiling Scala
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The current Scala version uses JRE classes such as `ClassLoader` or `SecurityContext` even in base Scala classes. These JRE classes do not make sense in a web agent context and are therefore not implemented in `j2js-jre`.
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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.
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So, sadly, we cannot support Scala under this circumstance.
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