Transformer API

The Transformer API provides convenient access to different transformers (currently decompilers only) under a unified API. The API is still subject to major changes, but only with a major version bump.

Installation

Maven

<dependency>
  <groupId>io.github.nbauma109</groupId>
  <artifactId>transformer-api</artifactId>
  <version>4.2.6</version>
</dependency>

Gradle

implementation 'io.github.nbauma109:transformer-api:4.2.6'

Gradle Kotlin DSL

implementation("io.github.nbauma109:transformer-api:4.2.6")

Usage

Currently, this API supports the following decompilers :

• Fernflower
• Vineflower (fork of Fernflower)
• Procyon
• CFR
• JD-Core V0 and V1
• JADX

Decompilers can be accessed either via StandardTransformers.Decompilers.ENGINE_* constants.

An example program decompiling a file using Vineflower (fork of Fernflower) is shown below:

package demo;

import com.heliosdecompiler.transformerapi.StandardTransformers;
import com.heliosdecompiler.transformerapi.common.Loader;

import jd.core.DecompilationResult;

import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;
import java.util.Map;
import org.apache.commons.io.IOUtils;

public class Sample {

    public byte[] load(String internalName) throws IOException {
        InputStream is = this.getClass().getResourceAsStream("/" + internalName + ".class");
        return is == null ? null : IOUtils.toByteArray(is);
    }

    public boolean canLoad(String internalName) {
        return this.getClass().getResource("/" + internalName + ".class") != null;
    }

    
    public static void main(String[] args) {
        Sample sample = new Sample();
        Loader loader = new Loader(sample::canLoad, sample::load);
        Map<String, String> preferences = new HashMap<>();
        try {
            String ff = StandardTransformers.Decompilers.ENGINE_VINEFLOWER;
            DecompilationResult result =
                    StandardTransformers.decompile(
                            loader,
                            "java/lang/String",
                            preferences,
                            ff
                    );
            System.out.println(result.getDecompiledOutput());
        } catch (Exception e) {
            System.err.println(e);
        }
    }
}

Features

• Agnostic loader utility
• In-memory decompilation (no temp files)

Updates

This API will be updated as decompilers receive updates, which means fixes reach you faster.

Software using transformer-api

JD-GUI DUO - Desktop GUI

ECD++ - Eclipse plugin

Third-party

By AgeloVito :

• JD Duo

Provides a comprehensive multi-decompiler toolkit and MCP server for Java, enabling deep analysis of bytecode and source code.

• jd-mcp-duo

A multi-decompiler MCP server and CLI toolkit for Java, supporting JD-Core v0 & v1, CFR, Procyon, Fernflower, Vineflower & JADX.