{"id":15220489,"url":"https://github.com/leonardosnt/java-class-tools","last_synced_at":"2025-10-30T07:30:20.599Z","repository":{"id":57279522,"uuid":"81487804","full_name":"leonardosnt/java-class-tools","owner":"leonardosnt","description":"Read and write java class files in Node.js or in the 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java-class-tools\n\n[![Build status](https://ci.appveyor.com/api/projects/status/dwfu9sq51uhofyyv?svg=true)](https://ci.appveyor.com/project/leonardosnt/java-class-tools)\n---\nThe 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.\n\n## Install\n```\nnpm install java-class-tools\n```\n\n## Examples:\n- [Browser usage example](https://rawgit.com/leonardosnt/java-class-tools/master/examples/browser.html) (List all methods and fields of a class file)\n- [Node usage example](https://repl.it/@leonardosnt/jct-example) (Simple disassembler)\n- [Try yourself](https://runkit.com/leonardosnt/java-class-tools-example)  (_RunKit:_ you must login with GitHub to be able to fork it)\n\nPrint method names (Node.js):\n```javascript\nconst { JavaClassFileReader } = require('java-class-tools');\nconst { TextDecoder } = require('util');\n\nconst reader = new JavaClassFileReader();\nconst classFile = reader.read('./Foo.class');\nconst textDecoder = new TextDecoder();\n\nclassFile.methods.forEach(md =\u003e {\n  /**\n   * Method name in constant-pool.\n   * \n   * Points to a CONSTANT_Utf8_info structure: https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.4.7\n   */\n  const nameInConstantPool = classFile.constant_pool[md.name_index];\n\n  // It is also possible to use the string_decoder builtin module.\n  const name = textDecoder.decode(new Uint8Array(nameInConstantPool.bytes));\n\n  console.log(name);\n});\n```\n\nPrint method names (Node.js):\n```html\n\u003cscript src=\"https://cdn.jsdelivr.net/npm/java-class-tools@latest/dist/java-class-tools.min.js\"\u003e\u003c/script\u003e\n\u003cscript\u003e\n  fetch('https://gist.githubusercontent.com/leonardosnt/69207dd9bcae55c93ff8fe6546c92eef/raw/fa008a94f9bc208cfa593cf568f0c504e3b30413/Class.class')\n    .then(r =\u003e r.arrayBuffer())\n    .then(printAllMethods);\n  \n  function printAllMethods(classData) {\n    const reader = new JavaClassTools.JavaClassFileReader();\n    const classFile = reader.read(classData);\n    const textDecoder = new TextDecoder();\n\n    classFile.methods.forEach(method =\u003e {\n      /**\n       * Method name in constant-pool.\n       * \n       * Points to a CONSTANT_Utf8_info structure: https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.4.7\n       */\n      const nameEntry = classFile.constant_pool[method.name_index];\n\n      const name = textDecoder.decode(new Uint8Array(nameEntry.bytes));\n\n      console.log(name);\n    });\n }\n\u003c/script\u003e\n```\n\n## License\nCopyright (C) 2017-2020 leonardosnt \u003c\u003cleonrdsnt@gmail.com\u003e\u003e  \nLicensed under the MIT License. See LICENSE file in the project root for full license information.\n\n","project_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Fleonardosnt%2Fjava-class-tools","html_url":"https://awesome.ecosyste.ms/projects/github.com%2Fleonardosnt%2Fjava-class-tools","lists_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Fleonardosnt%2Fjava-class-tools/lists"}