BouncyCastle: Android: Unsupported class file major version 59. Failed to transform bcprov-jdk15on-1.67.jar (org.bouncycastle:bcprov-jdk15on:1.67)
Introduction
This error arises when you attempt to integrate the BouncyCastle library (specifically, the bcprov-jdk15on dependency) into your Android project. This issue occurs because Android’s Java Virtual Machine (JVM) has a restriction on the Java class file major version it can support.
Understanding the Issue
* **Class File Major Version:** Java class files include a “major version” field that identifies the version of the Java compiler that generated the file.
* **BouncyCastle and Java Version:** The BouncyCastle library, specifically the `bcprov-jdk15on` artifact, is compiled using a newer version of Java (likely Java 11 or higher). This results in class files with a major version incompatible with Android’s JVM.
* **Android JVM Restrictions:** The Android JVM generally supports Java 8 or earlier class files.
* **Transformation Failure:** The `transform` task (part of Android’s build system) attempts to convert the BouncyCastle jar file into a version compatible with Android, but it fails due to the unsupported major version.
Resolution Strategies
1. Using the Correct BouncyCastle Artifact
* **Find a BouncyCastle Artifact Compatible with Android:** Search for an official BouncyCastle artifact specifically designed for Android. Look for versions labeled as `bcprov-android` or `bcprov-android-*.jar`. These artifacts are tailored for the Android platform and should resolve the major version incompatibility.
2. Adjusting Your Project’s Java Version
* **Modify Your Gradle Configuration:** Update the Java version used in your `build.gradle` file.
* **Example:**
“`gradle
android {
compileSdkVersion 33 // Adjust as needed
buildToolsVersion ‘30.0.3’ // Adjust as needed
// …other Android build settings
compileOptions {
sourceCompatibility JavaVersion.VERSION_1_8
targetCompatibility JavaVersion.VERSION_1_8
}
}
“`
3. Using Retrolambda (For Legacy Projects)
* **Retrolambda:** Retrolambda is a tool that allows you to run Java 8 bytecode on Android devices by converting it to Java 7 bytecode.
* **Installation:** Integrate Retrolambda into your project following its official instructions.
* **Caveats:** Retrolambda is a legacy solution, and might not be the most modern approach, especially with newer Android versions.
4. Alternative Cryptography Libraries
* **Explore Other Options:** If none of the above solutions work or if you encounter further issues, consider investigating alternative cryptography libraries specifically designed for Android:
* **SpongyCastle:** A library offering support for Android.
* **Conscrypt:** A library from Google for Android, potentially suitable for some use cases.
Debugging and Troubleshooting
* **Log Files:** Check your Android build output (usually located in the `build` directory) for error messages related to BouncyCastle and the unsupported class file version.
* **Dependency Management:** Double-check your dependencies. Make sure you’re not unintentionally including both the standard BouncyCastle and an Android-specific variant.
Conclusion
Resolving the “Unsupported class file major version 59” error with BouncyCastle involves finding a suitable artifact or adjusting your project’s settings to accommodate Android’s Java version limitations. Carefully analyze your dependencies and consider alternative cryptography libraries if necessary. This approach should ensure your project can successfully leverage BouncyCastle’s cryptographic capabilities on Android.