Web3j Documentation

To use Web3j in a Java project, add the following dependency to your pom.xml.

Important: Web3j Java binaries are compiled using Java 21. You must use Java 21 or a more recent version to use Web3j as a dependency.

For standard Java applications, use the core artifact. For Android applications, use the -android suffix version.

<!-- Standard Java (Requires Java 21+)
<dependency>
  <groupId>org.web3j</groupId>
  <artifactId>core</artifactId>
  <version>5.0.3</version>
</dependency>

<!-- Android
<dependency>
  <groupId>org.web3j</groupId>
  <artifactId>core</artifactId>
  <version>4.12.3-android</version>
</dependency>

Once the Web3j CLI is installed, you can initialize a new project by running the new command.

$ web3j new

Use the Web3j CLI to generate Java wrapper classes from a compiled .abi file. This allows you to interact with your smart contracts using type-safe Java code.

Arguments:

• -a: The path to the .abi file.
• -p: The target package name for the generated classes.
• -o: The output directory for the generated Java files.

The Web3j CLI can be used to create new projects and manage Ethereum-related tasks. Follow the installation instructions for your operating system:

Unix: Use curl to download and run the installer, then source the environment script.

Windows (PowerShell): Use the provided PowerShell command to bypass execution policy and run the installer script.

# Unix
curl -L get.web3j.io | sh && source ~/.web3j/source.sh

# Windows (PowerShell)
Set-ExecutionPolicy Bypass -Scope Process -Force; iex ((New-Object System.Net.WebClient).DownloadString('https://raw.githubusercontent.com/hyperledger/web3j-installer/main/installer.ps1'))

To generate the binary and ABI files for a Solidity contract, use the solc compiler with the following flags. Ensure you use the --overwrite flag if you need to replace existing files in the output directory.

solc --bin --abi --optimize --overwrite ${fileName}.sol -o build/

Web3j uses Gradle for its build process. You can run builds with or without integration tests.

Full build (excluding integration tests): Use ./gradlew check.

Running integration tests: Integration tests require a live Ethereum client and Docker. You must set the following environment variables to pull Docker images: registry.username and registry.password. Run with: ./gradlew -Pintegration-tests=true :integration-tests:test

Explicitly disabling integration tests: ./gradlew -Pintegration-tests=false :test

The ENS PublicResolver implements several Ethereum Improvement Proposals (EIPs) through different resolver profiles: