https://github.com/mrjameshamilton/jep457-hello-world-translator

A simple demonstration of transforming a class with the Java Class File API
https://github.com/mrjameshamilton/jep457-hello-world-translator

bytecode jep457 transform

Last synced: about 2 months ago
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A simple demonstration of transforming a class with the Java Class File API

• Host: GitHub
• URL: https://github.com/mrjameshamilton/jep457-hello-world-translator
• Owner: mrjameshamilton
• License: mit
• Created: 2024-03-16T15:36:31.000Z (9 months ago)
• Default Branch: master
• Last Pushed: 2024-03-20T19:26:20.000Z (9 months ago)
• Last Synced: 2024-03-20T20:41:51.665Z (9 months ago)
• Topics: bytecode, jep457, transform
• Language: Java
• Homepage: https://jameshamilton.eu/programming/jep-457-hello-world-translator
• Size: 3.91 KB
• Stars: 0
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# JEP457 Hello World Translator

[JEP 457 Class-File API](https://openjdk.org/jeps/457) is a preview API to provide a standard API for parsing, 

generating, and transforming Java class files.

The example here shows how easy it is to use to read and modify an existing class file. 

The example modifies a single `ldc` instruction to change the constant printed from "Hello World" to

another string provided as an argument.

For examples of generating a class from scratch see [JEP457 Hello World](https://github.com/mrjameshamilton/jep457-hello-world)

and [JEP457 Brainf*ck Compiler](https://github.com/mrjameshamilton/bf-jep457).

# Building

You'll need JDK 22.

The easiest way to install this on Linux is with [SDK man](https://sdkman.io/):

```shell

sdk install java 22-open

```

If you have Java 22, you can then execute the `run.sh` script which will

compile and execute `HelloWorld.java` and `HelloTranslator.java`.

`HelloTranslator` will transform `HelloWorld.class`, changing

the constant "Hello World" into the script argument,

and then executing it.

```shell

$ ./run.sh "Hallo Wereld"

```

# Similar projects

There are many similar projects for parsing,

generating, and transforming Java class files, including:

* [ASM](https://asm.ow2.io/)

* [ProGuardCORE](https://github.com/Guardsquare/proguard-core)

* [ByteBuddy](https://bytebuddy.net/#/)