Java2Smali

A comprehensive Android library for converting Java source code to Smali assembly language. Java2Smali provides a complete pipeline for transforming Java files into human-readable Smali code through compilation, dexing, and disassembly.

I made this for my other project ByteHaven and decided to distribute it for others to use because I couldnt find any other libararies like this that works on Android, and I made it easy to use.

Overview

Java2Smali orchestrates the complete transformation pipeline:

Compilation: Java source files → .class files (using javac)
Dexing: .class files → .dex files (using D8 or R8)
Disassembly: .dex files → .smali files (using baksmali)

Features

Dual Dexing Options: Support for both D8 (fast) and R8 (with optimization and obfuscation)
Classpath Management: Separate boot classpath (android.jar) and user classpath support
ProGuard Integration: Configurable ProGuard rules for R8 optimization
Status Callbacks: Real-time status updates for UI integration
Partial Pipeline Execution: Run individual stages (compile-only, compile+dex, etc.)
Multidex Support: Automatic handling of multiple DEX files
Thread-Safe: Asynchronous execution with proper concurrency controls

Requirements

Android API Level 26 or higher
Android Gradle Plugin 7.0+
Java 8 or higher

Installation

Gradle

Add the dependency to your module's build.gradle:

dependencies {
        implementation("io.github.tooldroidyt:java2smali:1.1.1")
}

Quick Start

Step-by-Step

1. Instantiate Java2Smali

// Instantiate Java2Smali
Java2Smali java2Smali = new Java2Smali(this);

2. Adding Java Sources

// Add individual Java source files
java2Smali.setSourceFiles(new File("path/to/Main.java"), new File("path/to/Example.java"));
// Or provide a source directory (recursively discovers .java files)
java2Smali.setSourceFiles(new File("path/to/src"));

// Set output directory for generated Smali files
java2Smali.setOutputFolder(new File("/output"));

// Set temporary working directory for intermediate build artifacts
java2Smali.setTempFolder(new File("/.build"));

3. Adding Dependencies

Files you might need (boot classes):

android.jar: needed when you use Android java api (eg. android.app.Activity)
core-lambda-stubs.jar: needed when the source you're gonna compile contains lambda syntax

// Boot classpath (e.g., android.jar): used for compilation only; not packaged
java2Smali.setBootClassPath(new File("android.jar"), new File("core-lambda-stubs.jar"));
// Alternatively, provide a directory containing framework jars
java2Smali.setBootClassPath(new File("path/to/folder/bootclasses"));

// Application classpath (e.g., mylibrary.jar): included in dex/smali output
java2Smali.setClassPath(new File("mylibrary.jar"), new File("morelibraries.jar"));
// Alternatively, provide a directory containing dependency jars
java2Smali.setClassPath(new File("path/to/folder/libraries"));

4. R8 Configuration

// Optional: custom ProGuard/R8 rules file
File proguardFile = new File("proguard-rules.pro");

java2Smali.useR8(
    true,  // enable R8 (use D8 when false)
    true,  // release mode (enables optimizations)
    true,  // allow code minification/shrinking
    proguardFile // ProGuard/R8 rules file (null to use defaults)
);

5. Listeners

// Listen to pipeline status updates (e.g., STARTING, COMPILING, DEXING)
java2Smali.setOnStatusListener(new OnStatusCallback() {
    @Override
    public void onStatus(Status status, String message) {
        Log.i("TAG", message);
    }
});

// Handle errors during compilation/dexing/disassembly
java2Smali.setOnErrorListener(new OnErrorCallback() {
    @Override
    public void onError(Exception exception) {
        // TODO: Handle error (e.g., show a message or retry)
    }
});

// Handle successful completion and use the output folder
java2Smali.setOnFinishListener(new OnFinishCallback() {
    @Override
    public void onFinish(File outputFolder) {
        // TODO: Use outputFolder (e.g., display path or open folder)
    }
});

// Run the full pipeline
java2Smali.start();

Full Example

// Instantiate Java2Smali
Java2Smali java2Smali = new Java2Smali(this);

// Add individual Java source files
java2Smali.setSourceFiles(new File("path/to/Main.java"), new File("path/to/Example.java"));
// Or provide a source directory (recursively discovers .java files)
java2Smali.setSourceFiles(new File("path/to/src"));

// Set output directory for generated Smali files
java2Smali.setOutputFolder(new File("/output"));

// Set temporary working directory for intermediate build artifacts
java2Smali.setTempFolder(new File("/.build"));

// Boot classpath (e.g., android.jar): used for compilation only; not packaged
java2Smali.setBootClassPath(new File("android.jar"), new File("core-lambda-stubs.jar"));
// Alternatively, provide a directory containing framework jars
java2Smali.setBootClassPath(new File("path/to/folder/bootclasses"));

// Application classpath (e.g., mylibrary.jar): included in dex/smali output
java2Smali.setClassPath(new File("mylibrary.jar"), new File("morelibraries.jar"));
// Alternatively, provide a directory containing dependency jars
java2Smali.setClassPath(new File("path/to/folder/libraries"));


// Optional: custom ProGuard/R8 rules file
File proguardFile = new File("proguard-rules.pro");

java2Smali.useR8(
    true,  // enable R8 (use D8 when false)
    true,  // release mode (enables optimizations)
    true,  // allow code minification/shrinking
    proguardFile // ProGuard/R8 rules file (null to use defaults)
);

// Listen to pipeline status updates (e.g., STARTING, COMPILING, DEXING)
java2Smali.setOnStatusListener(new OnStatusCallback() {
    @Override
    public void onStatus(Status status, String message) {
        Log.i("TAG", message);
    }
});

// Handle errors during compilation/dexing/disassembly
java2Smali.setOnErrorListener(new OnErrorCallback() {
    @Override
    public void onError(Exception exception) {
        // TODO: Handle error (e.g., show a message or retry)
    }
});

// Handle successful completion and use the output folder
java2Smali.setOnFinishListener(new OnFinishCallback() {
    @Override
    public void onFinish(File outputFolder) {
        // TODO: Use outputFolder (e.g., display path or open folder)
    }
});

// Run the full pipeline
java2Smali.start();

Configuration

Boot Classpath vs Classpath

Boot Classpath - Framework libraries used as references (not included in output):

android.jar
core-lambda-stubs.jar
Other Android framework JARs

Classpath - Application dependencies (included in output):

Your library JARs
Third-party dependencies (Gson, OkHttp, etc.)
Custom libraries

Annotation Warnings

When using libraries like Gson that reference optional annotation dependencies (Error Prone, JSR-305, etc.), Java2Smali automatically suppresses warnings. To disable:

java2smali.setIgnoreAnnotationWarnings(false);

This adds the following ProGuard rules automatically:

-dontwarn com.google.errorprone.annotations.**
-dontwarn javax.annotation.**
-dontwarn org.checkerframework.**
-dontwarn org.codehaus.mojo.animal_sniffer.**
-dontwarn edu.umd.cs.findbugs.annotations.**

API Reference

Constructors

`Java2Smali(Context context)`

Creates a compiler instance with minimal configuration. Use setter methods to configure.

Configuration Methods

Method	Description
`setSourceFiles(File... source)`	Sets Java source files or directories to compile
`setOutputFolder(File outputFolder)`	Sets the output directory for smali files
`setBootClassPath(File... jars)`	Sets boot classpath (framework JARs)
`setClassPath(File... jars)`	Sets user classpath (dependency JARs)
`setTempFolder(File tempFolder)`	Sets temporary directory for build artifacts
`useR8(boolean useR8, boolean release, boolean allowMinification, File proguardRules)`	Configures R8 dexing options
`setIgnoreAnnotationWarnings(boolean ignore)`	Controls annotation warning suppression

Callback Methods

Method	Description
`setOnStatusListener(OnStatusCallback callback)`	Sets callback for status updates
`setOnFinishListener(OnFinishCallback callback)`	Sets callback for successful completion
`setOnErrorListener(OnErrorCallback callback)`	Sets callback for error handling

Execution Methods

Method	Description
`start()`	Runs complete pipeline: Compile → Dex → Disassemble → Cleanup
`startUntilCompiling()`	Runs: Compile only
`startUntilDexing()`	Runs: Compile → Dex
`startUntilBackSmali()`	Runs: Compile → Dex → Disassemble (no cleanup)

Status Enum Values

public enum Status {
    STARTING,   // Pipeline initialization
    COMPILING,  // Java → .class
    DEXING,     // .class → .dex
    BAKSMALI,   // .dex → .smali
    CLEANING,   // Removing temporary files
    FINISHED,   // Complete success
    ERROR       // Fatal error occurred
}

Troubleshooting

"No Java compiler available"

Ensure you have javac available. On Android, the library includes an embedded javac.

"Missing class com.google.errorprone.annotations"

Enable annotation warning suppression:

compiler.setIgnoreAnnotationWarnings(true);

"Compilation failed to complete" with R8

Check your ProGuard rules. Try disabling minification:

compiler.useR8(true, true, false, null);

No .class files produced

Verify your source files are valid Java and the paths are correct:

File[] sources = compiler.getSourceFiles();
Log.d(TAG, "Found " + sources.length + " source files");

Architecture

┌─────────────────┐
│  Java Sources   │
│   (.java)       │
└────────┬────────┘
         │
         ▼
┌─────────────────┐
│     javac       │
│  (Compilation)  │
└────────┬────────┘
         │
         ▼
┌─────────────────┐
│  Class Files    │
│   (.class)      │
└────────┬────────┘
         │
         ▼
┌─────────────────┐
│   D8 or R8      │
│   (Dexing)      │
└────────┬────────┘
         │
         ▼
┌─────────────────┐
│   DEX Files     │
│   (.dex)        │
└────────┬────────┘
         │
         ▼
┌─────────────────┐
│    baksmali     │
│ (Disassembly)   │
└────────┬────────┘
         │
         ▼
┌─────────────────┐
│  Smali Files    │
│   (.smali)      │
└─────────────────┘

Dependencies

Android Tools R8: DEX compilation and optimization
Smali/Baksmali: DEX disassembly to Smali format
DexLib2: DEX file parsing and manipulation

License

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

Support

For issues, questions, or suggestions:

Open an issue on GitHub
Contact: notlifetechlolv2@gmail.com
Telegram: ByteHaven Pro

Acknowledgments

Inspired by Java2Smali by Belluxx
Android Open Source Project for R8/D8
JesusFreke for Smali/Baksmali
All contributors to this project

Name		Name	Last commit message	Last commit date
LICENSE		LICENSE
README.md		README.md

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Java2Smali

Overview

Features

Requirements

Installation

Gradle

Quick Start

Step-by-Step

Full Example

Configuration

Boot Classpath vs Classpath

Annotation Warnings

API Reference

Constructors

`Java2Smali(Context context)`

Configuration Methods

Callback Methods

Execution Methods

Status Enum Values

Troubleshooting

"No Java compiler available"

"Missing class com.google.errorprone.annotations"

"Compilation failed to complete" with R8

No .class files produced

Architecture

Dependencies

License

Support

Acknowledgments

About

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Repository files navigation

Java2Smali

Overview

Features

Requirements

Installation

Gradle

Quick Start

Step-by-Step

Full Example

Configuration

Boot Classpath vs Classpath

Annotation Warnings

API Reference

Constructors

Java2Smali(Context context)

Configuration Methods

Callback Methods

Execution Methods

Status Enum Values

Troubleshooting

"No Java compiler available"

"Missing class com.google.errorprone.annotations"

"Compilation failed to complete" with R8

No .class files produced

Architecture

Dependencies

License

Support

Acknowledgments

About

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`Java2Smali(Context context)`