How to generate JAR file dynamically compiling Java code in Kotlin
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This document discusses how to dynamically generate a JAR file by compiling Java code in Kotlin. It involves converting a Lisp AST to Java source code using a visitor pattern, compiling the Java code with Janino, extracting the Java bytecode using reflection, and creating a JAR file from the bytecode and dependent classes. Key steps include traversing the Lisp tree to generate Java source, using Janino to compile the source in-memory, accessing Janino's hidden bytecode field to obtain the bytecode, and packaging the bytecode and dependencies into a JAR file.
How to generate JAR file dynamically compiling Java code in Kotlin
- 1. How to generate JAR file dynamically compiling Java code in Kotlin Mitsunori Komatsu
- 2. About me • Mitsunori Komatsu, Software engineer at Treasure Data • github:komamitsu msgpack-java (jackson-dataformat-msgpack), fluency (yet another fluent logger java) treasuredata_fdw (with td-client-rust)
- 3. Why did I try it? • First, I developed just a tiny Lisp interpreter in Kotlin for exercise • But basically, interpreters aren’t so fast. So, I tried dynamically compiling Lisp code to Java byte code • Finally, I tried outputting those Java byte code to a JAR file
- 4. Where can we see the source code? https://github.com/komamitsu/tiny- kotlin-lisp
- 5. How did I do that? • Convert Lisp AST to Java source code traversing the tree using Visitor pattern • Compile the Java source code using http://janino-compiler.github.io/janino/ • Extract the Java byte code with a bit hack • Create a JAR file from the byte code and dependent classes
- 6. Convert Lisp AST to Java source code traversing the tree using Visitor pattern @CompileVisitor.kt Nothing special…
- 7. Convert Lisp AST to Java source code traversing the tree using Visitor pattern @CompileVisitor.kt Nothing special…
- 8. http://janino-compiler.github.io/janino/ With Janino!! Janino can not only compile a set of source files to a set of class files like JAVAC, but also compile a Java expression, block, class body or source file in memory, load the bytecode and execute it directly in the same JVM. Compile the Java source code
- 9. Compile the Java source code and Extract the Java byte code • It’s really easy to dynamically compile Java source code and invoke it with Janino • But Janino doesn’t provide any API to get compiled Java byte code…
- 10. Compile the Java source code and Extract the Java byte code Compile Extract Access a hidden field ByteArrayClassLoader.classes in Janino using reflection!@CompileVisitor.kt
- 11. Create a JAR file from the byte code and dependent classes Prepare dependent class files @CompileVisitor.kt Create the compiled class file Get Java byte code using Class#getResourceAsStream
- 12. Create a JAR file from the byte code and dependent classes @CompileVisitor.kt Setup a manifest Create a JAR file reading class files
- 13. Pitfalls @CompileVisitor.kt • When writing Kotlin code, it easily has dependencies with internal Kotlin classes (e.g kotlin.KotlinNullPointerException). So the classes are needed to be included in a JAR file to avoid runtime failures.