⚠️ PROJECT STATUS: Technology preview ⚠️

AIP-040 Non-Fungible Token — Reference Implementation

This project can be used directly to deploy non-fungible tokens on Aion AVM, and we recommend to use the NFToken class as the starting point for every Aion Java contract which will incorporate/extend non-fungible functionality.

Prerequisites

1. Supported operating systems are macOS, Linux and Windows
2. Install Java (version 11 or later) and Apache Maven
   • On macOS
     1. Do not use the official installer from Oracle, that approach is painful, nobody uses it
     2. Install Homebrew
     3. brew cask install java
     4. brew install maven

Building and testing

Prepare your Maven project build state

./mvnw initialize

Build and test

./mvnw clean install

A build which passes all tests will be indicated by:

[INFO] BUILD SUCCESS

at the bottom of your build.

After you have made any changes, run the build and test command above.

Overview

• AVMBlockchainWrapper is a wrapper around the current AVM storage API.
• AIP040Encoder is an encoder for any contract to interrogate any AIP-040 contract, use this to make type safe method calls which it converts to ABI encoded, wire-ready bytecode.
• AIP040Events is an output encoder for any AIP-040 contract to emit events, use this to pass type safe calls which it directly logs to the blockchain.
• NFToken{,Storage} are a base class and storage details for implementing the standardized AIP-040 behavior.
• NFTokenMock{,Encoder} are a useful implementation and encoder which has additional functionality which we believe many people will want, but which is not standardized.
• Main{,Encoder} are a deployable contract and encoder to access it.

Notes:

• We expect the AVM storage API will change in the future, and the wrapper will be promoted upstream, obviating the need to include it in this project. aionnetwork/AVM#399.

• The encoders are boilerplate code which should be generated from a Java interface. Java does not support class (not instance) methods with dynamic dispatch, so we cannot make an interface for Aion contracts. This is a shortcoming of Java and should be addressed as a Java Specification Request. Please help.

Extending

If you extend the functionality of the token implementation, for example to add pausing, extend the provided implementation.

To incorporate non-fungible tokens into your contract, which may have other features, copy the AIP-040 boilerplate code from the provided Main.java.

References

• Style, comments
  • Oracle style guide for doc comments https://www.oracle.com/technetwork/java/javase/documentation/index-137868.html#styleguide
    • What words to capitalize (refer examples), when to use periods and full sentences
    • "Include tags in the following order"
    • Align text to columns
  • Minimal requirements from https://github.com/aionnetwork/aion/wiki/Aion-Code-Conventions
  • Not required by Aion, but adopting method naming requirements from https://google.github.io/styleguide/javaguide.html
  • Code reuse pattern for separating an interface specification, a reference implementation, usage demonstrations, testing subjects and other tools. https://github.com/0xcert/ethereum-erc721#structure
• Which version of dependencies we should support
  • Aion supports JDK version 11 https://docs.aion.network/docs/environment-variables
  • Java versions supported by vendor https://www.oracle.com/technetwork/java/java-se-support-roadmap.html
• Aion protocol design
  • Yes, null can be passed in the ABI https://github.com/aionnetwork/AVM/blob/master/org.aion.avm.userlib/src/org/aion/avm/userlib/abi/ABIEncoder.java#L387-L390

• Setting up a Java + Maven + JUnit + Aion project layout
  • Best practice for Java+Maven+JUnit project layout https://github.com/junit-team/junit5-samples/tree/master/junit5-jupiter-starter-maven
  • How to remove Maven initialization errors https://stackoverflow.com/questions/4123044/maven-3-warnings-about-build-plugins-plugin-version
  • pom.xml for AVM Maven projects https://github.com/satran004/avm-samples/blob/master/HelloAvm/pom.xml
  • Gitignore for Maven projects ("should I include jars?") #25
• Gitignore from https://github.com/github/gitignore/blob/master/Maven.gitignore
• Editorconfig is included and some rules are referenced to Google Java Style Guide

Maintenance

• Periodically update to the most recent version, to obtain the latest bug fixes and new features:

  mvn versions:use-latest-versions -Dincludes="org.checkerframework:*"

• Periodically update mvnw if necessary. We recognize upstream as https://github.com/takari/maven-wrapper

• Periodically review AVM and other Maven dependencies and update if necessary:

  mvn aion4j:init -DforceCopy

License

This project is assigned copyright to Aion Foundation and released under the MIT license. Thank you to Aion Foundation for sponsoring this work!