https://github.com/leonardosnt/java-class-tools

Read and write java class files in Node.js or in the browser.
https://github.com/leonardosnt/java-class-tools

assembler browser class disassembler java javascript node parser reader writer

Last synced: 4 months ago
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Read and write java class files in Node.js or in the browser.

• Host: GitHub
• URL: https://github.com/leonardosnt/java-class-tools
• Owner: leonardosnt
• License: mit
• Created: 2017-02-09T19:40:07.000Z (almost 8 years ago)
• Default Branch: master
• Last Pushed: 2023-09-19T18:08:49.000Z (over 1 year ago)
• Last Synced: 2024-09-29T13:10:41.923Z (4 months ago)
• Topics: assembler, browser, class, disassembler, java, javascript, node, parser, reader, writer
• Language: JavaScript
• Homepage:
• Size: 453 KB
• Stars: 37
• Watchers: 5
• Forks: 8
• Open Issues: 2
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# java-class-tools

[![Build status](https://ci.appveyor.com/api/projects/status/dwfu9sq51uhofyyv?svg=true)](https://ci.appveyor.com/project/leonardosnt/java-class-tools)

---

The structure of the ClassFile object returned by `JavaClassFileReader#read` and its _inner objects_ matches the [Java Virtual Machine Specification](https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html), therefore you can use this specification as a guide on how to understand and change a Class file.

## Install

```

npm install java-class-tools

```

## Examples:

- [Browser usage example](https://rawgit.com/leonardosnt/java-class-tools/master/examples/browser.html) (List all methods and fields of a class file)

- [Node usage example](https://repl.it/@leonardosnt/jct-example) (Simple disassembler)

- [Try yourself](https://runkit.com/leonardosnt/java-class-tools-example)  (_RunKit:_ you must login with GitHub to be able to fork it)

Print method names (Node.js):

```javascript

const { JavaClassFileReader } = require('java-class-tools');

const { TextDecoder } = require('util');

const reader = new JavaClassFileReader();

const classFile = reader.read('./Foo.class');

const textDecoder = new TextDecoder();

classFile.methods.forEach(md => {

  /**

   * Method name in constant-pool.

   * 

   * Points to a CONSTANT_Utf8_info structure: https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.4.7

   */

  const nameInConstantPool = classFile.constant_pool[md.name_index];

  // It is also possible to use the string_decoder builtin module.

  const name = textDecoder.decode(new Uint8Array(nameInConstantPool.bytes));

  console.log(name);

});

```

Print method names (Node.js):

```html

  fetch('https://gist.githubusercontent.com/leonardosnt/69207dd9bcae55c93ff8fe6546c92eef/raw/fa008a94f9bc208cfa593cf568f0c504e3b30413/Class.class')

    .then(r => r.arrayBuffer())

    .then(printAllMethods);

  

  function printAllMethods(classData) {

    const reader = new JavaClassTools.JavaClassFileReader();

    const classFile = reader.read(classData);

    const textDecoder = new TextDecoder();

    classFile.methods.forEach(method => {

      /**

       * Method name in constant-pool.

       * 

       * Points to a CONSTANT_Utf8_info structure: https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.4.7

       */

      const nameEntry = classFile.constant_pool[method.name_index];

      const name = textDecoder.decode(new Uint8Array(nameEntry.bytes));

      console.log(name);

    });

 }

```

## License

Copyright (C) 2017-2020 leonardosnt <>  

Licensed under the MIT License. See LICENSE file in the project root for full license information.