Web3j

Web3j

This skill is for AI agents helping users consume the Web3j library and CLI.

Treat Web3j as two separate interfaces:

• Java library usage inside application code
• Web3j CLI usage from the shell

Do not blur these together. If the user asks for code inside a Java project, answer with the library APIs. If the user asks to scaffold a project, audit Solidity, or manage wallets from the terminal, answer with the CLI.

Routing

• For contributing to the Web3j library itself, including bug reports, fixes, feature proposals, formatting, PR expectations, and community discussion paths, read references/contributing.md.
• For project setup, dependency selection, module guidance, and "how do I use this library", read references/getting-started.md.
• For end-to-end ERC20 examples that show how CLI scaffolding, wrapper generation, interaction, tests, and events fit together, read references/erc20-example.md.
• For event subscriptions, filters, flowables, WebSocket pub/sub, and runnable starter examples, read references/events.md.
• For smart contract wrapper generation, deployment, loading, calling, sending transactions, contract event subscriptions, and raw transaction fallbacks, read references/smart-contracts.md.
• For web3j new, web3j import, web3j run, web3j docker run, web3j wallet create, web3j wallet update, web3j wallet send, web3j audit, and OpenAPI-oriented CLI scaffolding, read references/cli.md.
• For Gradle and Maven plugin workflows, read references/build-plugins.md.
• For private transactions, Besu/EEA privacy APIs, and permissioned-network configuration context, read references/privacy-permissioning.md.
• For transaction managers, signing, gas, nonces, EIP transaction types, wallet files, ETH transfers, generic log filters, and block/transaction flowables, read references/transactions.md.
• For the broader Web3j ecosystem tools named directly by the user, read:
  • references/web3j-eth2-client.md
  • references/web3j-openapi.md
  • references/web3j-unit.md
  • references/web3j-evm.md
  • references/web3j-sokt.md

Repo-grounded examples

When you need canonical implementation patterns, prefer these local sources:

• README.md for published dependency coordinates, Java version expectations, and high-level positioning
• integration-tests/src/test/java/org/web3j/protocol/scenarios/FunctionWrappersIT.java for generated wrapper deploy/load/call patterns
• integration-tests/src/test/java/org/web3j/protocol/scenarios/DeployContractIT.java for lower-level raw contract deployment and ABI calls
• integration-tests/src/test/java/org/web3j/protocol/scenarios/SendEtherIT.java for ETH transfers and Transfer.sendFunds
• integration-tests/src/test/java/org/web3j/protocol/core/FlowableIT.java for block, transaction, pending-transaction, log, and replay flowables
• integration-tests/src/test/java/org/web3j/protocol/scenarios/EventFilterIT.java for manual EthFilter-based event filtering and log decoding
• core/src/main/java/org/web3j/crypto/WalletUtils.java for wallet creation and credential loading APIs
• core/src/main/java/org/web3j/tx/RawTransactionManager.java for local signing and raw transaction broadcast patterns
• integration-tests/build.gradle for web3j-unit usage in this repo's test setup
• integration-tests/src/test/java/org/web3j/protocol/besu/BesuPrivacyQuickstartIntegrationTest.java for private transaction and privacy group flows
• besu/src/main/java/org/web3j/tx/PrivateTransactionManager.java and eea/src/main/java/org/web3j/protocol/eea/crypto/RawPrivateTransaction.java for privacy APIs
• contracts/scripts/generateWrappers.sh and codegen/src/main/java/org/web3j/codegen/SolidityFunctionWrapperGenerator.java for wrapper-generation CLI shape

Working rules

• Prefer concise, copyable answers.
• Separate "library code" from "CLI commands" with explicit headings when both are relevant.
• If the user asks to create a new project, first decide whether they mean:
  • a CLI-scaffolded Web3j project
  • a CLI import or generated-project workflow
  • adding Web3j to an existing Maven or Gradle Java project
• If the user asks how to contribute to Web3j itself, first decide whether they mean:
  • report a bug
  • submit a fix
  • propose a feature
  • ask a source-code question
• For dependency coordinates and install steps, prefer official published usage from the docs and README.md.
• For implementation details, prefer this repo's source and integration tests.
• When showing smart contract usage, default to generated wrappers first and raw ABI / raw transaction flows second.
• When the user asks for a basic ERC20 example or how Web3j pieces fit together across wrappers, tests, and events, prefer the starter assets under assets/erc20-example/.
• When the user asks for a runnable event-listening example, prefer the starter assets under assets/event-subscriptions/ and adapt the closest template instead of writing one from scratch.
• When answering audit questions, make clear that web3j audit is static analysis from the CLI toolchain, not a Java runtime API.
• When answering OpenAPI, Unit, EVM, Sokt, or Eth2 questions, be explicit when the docs describe a companion library or generated project rather than a package implemented in this repo's main modules.
• When helping with repo contributions, follow CONTRIBUTING.md: bug issues should include a real reproducer, fixes should be formatted with Spotless, and feature ideas should go through Discord discussion before GitHub issue creation.