Top 10 Java Bytecode Manipulation Projects

bytecode-viewer

4 13,757 2.1 Java

A Java 8+ Jar & Android APK Reverse Engineering Suite (Decompiler, Editor, Debugger & More)

Project mention: Java 泛型程式設計的注意事項 | dev.to | 2023-01-02
Byte Buddy

2 5,575 9.2 Java

Runtime code generation for the Java virtual machine.

Project mention: Any news on the Classfile API? | /r/java | 2022-12-23

Just a drive-by comment: ByteBuddy is worth a look https://bytebuddy.net/. It is built on top of ASM.
Sonar

www.sonarsource.com
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Recaf

6 4,934 2.2 Java

The modern Java bytecode editor

Project mention: what is the easiest way to decompile, edit and recompile a mod? | /r/feedthebeast | 2022-10-11

IF you've got the legal situation all sorted out, and know that you need to change a Java class file, and know how to program in Java, I'd suggest Recaf. With it, you can import a jar file, decompile, edit and recompile any source files in it, and export the whole thing again.
Javassist

1 3,838 3.8 Java

Java bytecode engineering toolkit

Project mention: JUnit 5: link tests with task tracker issues | dev.to | 2023-04-21

ClassPool comes from Javaassist library. It gives convenient API to retrieve the line number of Java method.
Mixin

6 1,150 0.0 Java

Mixin is a trait/mixin and bytecode weaving framework for Java using ASM

Project mention: Hello I would try to start Modding in Minecraft. Have you any advice or good tutorial for beginning ? | /r/CurseForge | 2022-12-13

And one day maybe you'll need that to inject code into specific location, but it's to do advanced things: https://github.com/SpongePowered/Mixin/wiki
threadtear

1 733 0.0 Java

Multifunctional java deobfuscation tool suite

Project mention: does decompiling a .jar file execute it? | /r/java | 2022-07-18

If you're very paranoid, Threadtear does have some amount of protection against potential code execution when decompiling, although it hasn't been updated in a while and it's still always a risk (albeit one I never personally encountered). If you suspect that the file you want to decompile does have a way to execute code when decompiling it, you could try using a virtual machine for some added protection.
Byteman

0 460 0.0 Java

Byteman Project main repo
InfluxDB

www.influxdata.com
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Access the most powerful time series database as a service. Ingest, store, & analyze all types of time series data in a fully-managed, purpose-built database. Keep data forever with low-cost storage and superior data compression.
yGuard

1 289 3.2 Java

The open-source Java obfuscation tool working with Ant and Gradle by yWorks - the diagramming experts

Project mention: Obfuscation tutorial (the sequel) | /r/minecraftclients | 2022-07-31
MixinExtras

1 154 10.0 Java

Companion library to SpongePowered Mixin with many custom injectors for a more expressive experience.

Project mention: Need help to fix error | /r/fabricmc | 2023-05-16

Try adding the jar here https://github.com/LlamaLad7/MixinExtras/releases/tag/0.1.1
Maker

4 36 5.9 Java

Lightweight, full-featured, low-level dynamic Java class generator designed for ease of use.

Project mention: Any news on the Classfile API? | /r/java | 2022-12-23

If you want an alternative to ASM, try Cojen/Maker, which is designed to be much easier to use than any of the other class writing APIs, including the one proposed by JEP-8280389. Here's a comparison.

NOTE: The open source projects on this list are ordered by number of github stars. The number of mentions indicates repo mentiontions in the last 12 Months or since we started tracking (Dec 2020). The latest post mention was on 2023-05-16.