One crucial point to achieve business adoption of æternity is the ease of use and integration of smart contracts. With the contraect-maven-plugin we want to bridge this gap and allow the interaction with smart contracts by leveraging well established languages based on the JVM like Java, Kotlin and Scala.

Due to it’s maven nature, the plugin can be seemlessly integrated into the build process. Based on a Sophia smart contract, the plugin analyses the contract source and provides a convienient way to interact with the blockchain, for example deploying the contract or call a contracts function using the aepp-sdk-java. Using strongly typed input and output parameters for contract calls renders the need for encoding and decoding and helps reducing errors.

How it works

Technically, the plugin generates a Java class for every contract using the JavaPoet Library which forms the basis for the interaction with a contract. The generated class contains

  • methods to deploy the contract or reuse an already existing contract
  • all contract’s callable function entrypoints (stateful, stateless, payable)
  • the contract’s state types
  • all default datatypes like address and hash
  • all declared custom types, necessary for function entrypoints

The plugin uses the æternity http compiler to create an analyzable JSON format which is subsequently parsed for the respective data types and functions. Though, the input and output parameters of function are mapped from the Sophia datatypes to the corresponding Java datatypes, which can be arbitrary nested. Given that all necessary datatypes are declared within one Java class, the generated contract can be used standalone as is. All necessary dependencies are shipped through the maven dependency declaration.

To interact with the chain, contract entrypoint functions are executed using the aepp-sdk-java. The target network (testnet or mainnet) can be easily configured – further details can be found in the contraect-maven-plugin documentation.


  • the necessary fee required to execute a transaction is automatically calculated by the aepp-sdk-java

The source code of the contraect-maven-plugin is available on GitHub.


In case you would like to test working with the contraect-maven-plugin we created contraect-showcase-maven, a repository where you can find different examples how to test Sophia smart contracts using the plugin and the SDK.

Any problems?

If you encounter problems using the plugin please create a ticket on Github and we will try to help you as soon as possible.

If you have any general questions about the plugin, please visit the official forum.

Product: Maven plugin
Blockchain: æternity
Technologies: Java, Maven
Repository: contraect-maven-plugin