# jboss-javassist/javassist

Java bytecode engineering toolkit

Repository: https://github.com/jboss-javassist/javassist
Canonical: https://ross.abutalabs.com/products/javassist
Language: Java
License: NOASSERTION
License Family: other
Topics: java-bytecode, java
Last push: 2026-08-23T15:28:01+00:00

## Health v2 (maintenance only)
Score: 95/100 (v2, computed 2026-09-02T17:46:02.011165+00:00)
- activity 99, release rhythm 87, longevity 100
- inputs: {"age_days": 4849, "days_push": 10, "days_rel": 10, "gap_med": 62.5, "n_releases_24m": 3}
- flags: no_license
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 4228, forks 717 (observed 2026-08-28T04:08:39.390648+00:00)

## What it is
Javassist is a Java class library for editing Java bytecode, enabling programs to define new classes at runtime or modify class files as the JVM loads them. It offers both a source-level API (editing classes using Java syntax without bytecode knowledge) and a bytecode-level API for direct class file manipulation.

## Use cases
- generate new Java classes at runtime
- instrument Java classes as the JVM loads them
- modify class files without knowing bytecode internals
- build AOP frameworks or proxies in Java
- add logging or tracing to existing Java classes
- patch third-party Java libraries at load time

## When to choose
- you need runtime class generation or bytecode transformation on the JVM
- you want to edit classes using Java source syntax instead of raw bytecode
- you're building frameworks like ORMs, AOP tools, or mocking libraries

## When to avoid
- you need bytecode manipulation on non-JVM languages
- you only need runtime reflection without class modification
- you need a higher-level agent framework rather than a bytecode library

## Facets
- artifact type: library
- maturity: stable
- function: compiler, parser, developer-tools
- domain: developer-tools, programming-languages, compilers
- platform: jvm
- tags: bytecode-manipulation, java-bytecode, runtime-class-generation, instrumentation, aop

## Member repositories
- jboss-javassist/javassist (main) score 95

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:08:39.390648+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-29T18:22:21.637529+00:00, confidence not recorded.
  - readme: https://github.com/jboss-javassist/javassist (fetched 2026-08-28T04:08:39.390648+00:00, sha a7e9508dde9e)
- Data as of 2026-08-30T08:39:29.467469+00:00.