https://github.com/sunwu51/swapper

jvm diagnose tool by swapping bytecode
https://github.com/sunwu51/swapper

asm attach bytecode debugging-tool diagnose hotswap javassist jvm

Last synced: 9 days ago
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jvm diagnose tool by swapping bytecode

• Host: GitHub
• URL: https://github.com/sunwu51/swapper
• Owner: sunwu51
• License: mit
• Created: 2023-11-26T15:44:38.000Z (over 2 years ago)
• Default Branch: master
• Last Pushed: 2026-06-19T07:02:05.000Z (11 days ago)
• Last Synced: 2026-06-19T08:27:37.583Z (11 days ago)
• Topics: asm, attach, bytecode, debugging-tool, diagnose, hotswap, javassist, jvm
• Language: Java
• Homepage: https://www.bilibili.com/video/BV1TmWWeYEie
• Size: 40.9 MB
• Stars: 86
• Watchers: 2
• Forks: 21
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

          
# JVM ByteSwap Tool

![logo](sw-ico.png)

![actions](https://github.com/sunwu51/JVMByteSwapTool/actions/workflows/main.yml/badge.svg)

A tool that can hot swap the class byte code while jvm is running. Very suitable for `SpringBoot framework`.

Based on the jvm instrumentation tech, ASM, javassist and JVMTI.

# Usage

Download `swapper.jar` from the [release](https://github.com/sunwu51/JVMByteSwapTool/releases) page.

Make sure you have a JDK >= 1.8.

```bash

$ java -jar swapper.jar

// All of the java processes will be listed

// Choose the pid you want to attach

// Then the backend service will start

```

If you want to change the HTTP server port or WebSocket port:

```bash

$ java -jar -Dw_http_port=9999 -Dw_ws_port=19999 swapper.jar

```

## Web UI

After `swapper.jar` starts, visit `http://localhost:8000` and use the Web UI.

![image](https://i.imgur.com/WSKkrxX.png)

Now you can enjoy the functionalities of swapper tool.

For example, `Watch` some methods. Trigger this method, and then the params and return value and execution time cost will be printed. 

![image](https://i.imgur.com/RaEZ1w5.png)

It's `Watch` one of the functions provided by swapper tool.

Get more functions and details from the [wiki](https://github.com/sunwu51/JVMByteSwapTool/wiki).

## TUI CLI

You can use the TUI client in the same way as the Web UI.

Install it from npm:

```bash

$ npm i -g jbs-client

$ jbs-client

```

Or download the standalone binary for your platform from the [jbs-client-opentui releases](https://github.com/sunwu51/jbs-client-opentui/releases), then run:

```bash

$ jbs-client

```

The interaction flow is consistent with the Web UI.

![img](https://i.imgur.com/5HTimiI.png)