├── .gitignore ├── Artboard.png ├── src └── main │ ├── test │ └── java │ │ └── org │ │ └── web3j │ │ └── sample │ │ └── GreeterContractIT.java │ ├── resources │ └── logback.xml │ ├── solidity │ └── Greeter.sol │ └── java │ └── org │ └── web3j │ └── sample │ └── Application.java ├── pom.xml ├── README.md └── LICENSE /.gitignore: -------------------------------------------------------------------------------- 1 | .idea/ 2 | target/ -------------------------------------------------------------------------------- /Artboard.png: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/web3j/sample-project-maven/HEAD/Artboard.png -------------------------------------------------------------------------------- /src/main/test/java/org/web3j/sample/GreeterContractIT.java: -------------------------------------------------------------------------------- 1 | package org.web3j.sample; 2 | 3 | import org.junit.Test; 4 | 5 | /** 6 | * Integration test to run our main application. 7 | */ 8 | public class GreeterContractIT { 9 | 10 | @Test 11 | public void testGreeterContract() throws Exception { 12 | Application.main(new String[]{ }); 13 | } 14 | } 15 | -------------------------------------------------------------------------------- /src/main/resources/logback.xml: -------------------------------------------------------------------------------- 1 | 2 | 3 | 4 | 5 | 6 | %d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | -------------------------------------------------------------------------------- /src/main/solidity/Greeter.sol: -------------------------------------------------------------------------------- 1 | pragma solidity ^0.4.24; 2 | 3 | // Modified Greeter contract. Based on example at https://www.ethereum.org/greeter. 4 | 5 | contract Mortal { 6 | /* Define variable owner of the type address*/ 7 | address owner; 8 | 9 | /* this function is executed at initialization and sets the owner of the contract */ 10 | constructor () public { owner = msg.sender; } 11 | 12 | /* Function to recover the funds on the contract */ 13 | function kill() public { if (msg.sender == owner) selfdestruct(owner); } 14 | } 15 | 16 | contract Greeter is Mortal { 17 | /* define variable greeting of the type string */ 18 | string greeting; 19 | 20 | /* this runs when the contract is executed */ 21 | constructor (string _greeting) public { 22 | greeting = _greeting; 23 | } 24 | 25 | function newGreeting(string _greeting) public { 26 | emit Modified(greeting, _greeting, greeting, _greeting); 27 | greeting = _greeting; 28 | } 29 | 30 | /* main function */ 31 | function greet() public constant returns (string) { 32 | return greeting; 33 | } 34 | 35 | /* we include indexed events to demonstrate the difference that can be 36 | captured versus non-indexed */ 37 | event Modified( 38 | string indexed oldGreetingIdx, string indexed newGreetingIdx, 39 | string oldGreeting, string newGreeting); 40 | } 41 | -------------------------------------------------------------------------------- /pom.xml: -------------------------------------------------------------------------------- 1 | 2 | 5 | 4.0.0 6 | 7 | org.web3j.sample 8 | sample-project-maven 9 | 1.0.0-SNAPSHOT 10 | 11 | 12 | 3.6.0 13 | 1.2.3 14 | 0.3.7 15 | 4.12 16 | 1.6.0 17 | 1.8 18 | 1.8 19 | 20 | 21 | 22 | 23 | org.web3j 24 | core 25 | ${web3j.version} 26 | 27 | 28 | ch.qos.logback 29 | logback-classic 30 | ${logback-classic.version} 31 | runtime 32 | 33 | 34 | junit 35 | junit 36 | ${junit.version} 37 | 38 | 39 | 40 | 41 | 42 | 43 | org.web3j 44 | web3j-maven-plugin 45 | ${web3j-maven-plugin.version} 46 | 47 | 48 | src/main/solidity 49 | 50 | *.sol 51 | 52 | 53 | 54 | 55 | 56 | org.codehaus.mojo 57 | exec-maven-plugin 58 | ${exec-maven-plugin} 59 | 60 | org.web3j.sample.Application 61 | 62 | 63 | 64 | 65 | 66 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # web3j Sample Project 2 | 3 | This project provides a very simple starter application for working with web3j and the test 4 | Ethereum network (testnet) known as Rinkeby. 5 | 6 | The demo deploys a *hello world* smart contract which contains a greeting message. The current 7 | greeting message can be read and modified in the smart contract. 8 | 9 | In order to run this demo, three pieces of information are required: 10 | 11 | 1. Ethereum client (or node) endpoint. The simplest thing to do is 12 | [request a free access token](https://infura.io/register.html) from Infura. 13 | 2. A wallet file. This can be generated using the web3j 14 | [command line tools](https://docs.web3j.io/command_line.html) by running the command: 15 | 3. Some Ether. This can be requested from the [Rinkeby Faucet](https://www.rinkeby.io/#faucet). 16 | 17 | - To create a wallet file, run the command: 18 | ```aidl 19 | web3j wallet create 20 | ``` 21 | 22 | - You will be asked to secure your wallet with a password. You will have the option 23 | of choosing a destination directory for your wallet file. 24 | In the `Application.java` class under the package `org.web3j.sample`, 25 | on line `66-67` replace the placeholders with your wallet file password and directory path. 26 | 27 | - With the access token retrieved from Infura, on line `58` replace the placeholder 28 | in the url with your token. You can find this under the `Endpoint` section: 29 | 30 | ![Alt text](Artboard.png) 31 | 32 | Once these details have been added to the main Application class, you'll be good to go. 33 | 34 | ### Run the project 35 | - Make sure to be in the root directory 36 | - First we need to create the smart contracts deriving from the solidity file `Greeter.sol` by running: 37 | ```aidl 38 | mvn web3j:generate-sources 39 | ``` 40 | - This will create the Greeter and Mortal contract under the package `org.web3j.model` 41 | - Clean and build the project, run the command: 42 | ```aidl 43 | mvn install 44 | ``` 45 | This will also generate a jar file with all the dependencies which we will run once 46 | it has been created. 47 | - Run the `Main` method in `Application.java` by running 48 | ``` 49 | mvn exec:java 50 | ``` 51 | - Alternatively, you can run the `main` method in `Application.java` in your chosen IDE, e.g. `IntelliJ` 52 | 53 | ## Functionality 54 | 55 | This application demonstrates a number of core features of web3j and Ethereum: 56 | 57 | - Connecting to a node on the Ethereum network 58 | - Loading an Ethereum wallet file 59 | - Sending Ether from one address to another 60 | - Deploying a smart contract to the network 61 | - Reading a value from the deployed smart contract 62 | - Updating a value in the deployed smart contract 63 | - Viewing an event logged by the smart contract 64 | 65 | 66 | ## Background 67 | 68 | This application has purposefully been kept as simple as possible with the aim of demonstrating 69 | how to deploy and work with a smart contract on the decentralised Ethereum network. 70 | 71 | If you require further background information about the above configuration items for the project 72 | you can refer to the below. 73 | 74 | For a more comprehensive overview, I recommend you read the 75 | [Java Magazine Article](https://web3j.io/articles/web3j%20article%20-%20Java%20Magazine%20JanuaryFebruary%202017.pdf), watch 76 | the 77 | [YouTube](https://youtube.com/watch?v=ea3miXs_P6Y) talk, and read all of the 78 | [documentation](https://docs.web3j.io). 79 | 80 | ### Smart contracts 81 | 82 | The contained smart contract is based on the 83 | [Greeter contract example](https://www.ethereum.org/greeter), with the addition that the value 84 | stored in the Greeter can be modified. 85 | 86 | The associated Java smart contract wrapper is named Greeter. 87 | 88 | For more background on smart contracts, refer to the 89 | [smart contracts](https://docs.web3j.io/smart_contracts.html) section of the docs. 90 | 91 | 92 | ### Infura 93 | 94 | If you don't want to sign up to Infura, and would like to run a node yourself, there are 95 | instructions in the [getting started](https://docs.web3j.io/getting_started.html#start-a-client) 96 | section of the docs. 97 | 98 | ### Testnets 99 | 100 | For more information on the different Ethereum test networks (or testnets), refer 101 | to the 102 | [testnet overview](https://docs.web3j.io/transactions.html#ethereum-testnets) in the docs. 103 | 104 | ### Ether 105 | 106 | For background on Ether, refer to the transactions 107 | [overview](https://docs.web3j.io/transactions.html#transactions) section of the docs. 108 | 109 | ### Wallets and transaction signing 110 | 111 | For a more technical overview of working with wallet files, refer to the 112 | [Offline transaction signing](https://docs.web3j.io/transactions.html#offline-transaction-signing) 113 | section of the docs. 114 | 115 | 116 | ## Viewing requests 117 | 118 | A logback configuration is included in the project dependencies allowing the logging of protocol 119 | messages if required. To enable, simply change the following [line]() in the logback configuration 120 | to read: 121 | 122 | ```xml 123 | 124 | ``` 125 | -------------------------------------------------------------------------------- /src/main/java/org/web3j/sample/Application.java: -------------------------------------------------------------------------------- 1 | package org.web3j.sample; 2 | 3 | import org.slf4j.Logger; 4 | import org.slf4j.LoggerFactory; 5 | import org.web3j.crypto.Credentials; 6 | import org.web3j.crypto.WalletUtils; 7 | import org.web3j.model.Greeter; 8 | import org.web3j.protocol.Web3j; 9 | import org.web3j.protocol.core.methods.response.TransactionReceipt; 10 | import org.web3j.protocol.http.HttpService; 11 | import org.web3j.tx.Transfer; 12 | import org.web3j.tx.gas.ContractGasProvider; 13 | import org.web3j.tx.gas.DefaultGasProvider; 14 | import org.web3j.utils.Convert; 15 | import org.web3j.utils.Numeric; 16 | 17 | import java.math.BigDecimal; 18 | 19 | /** 20 | * A simple web3j application that demonstrates a number of core features of web3j: 21 | * 22 | *
    23 | *
  1. Connecting to a node on the Ethereum network
    2. 24 | *
  2. Loading an Ethereum wallet file
    3. 25 | *
  3. Sending Ether from one address to another
    4. 26 | *
  4. Deploying a smart contract to the network
    5. 27 | *
  5. Reading a value from the deployed smart contract
    6. 28 | *
  6. Updating a value in the deployed smart contract
    7. 29 | *
  7. Viewing an event logged by the smart contract
    8. 30 | *
31 | * 32 | *

To run this demo, you will need to provide: 33 | * 34 | *

    35 | *
  1. Ethereum client (or node) endpoint. The simplest thing to do is 36 | * request a free access token from Infura
    2. 37 | *
  2. A wallet file. This can be generated using the web3j 38 | * command line tools
    3. 39 | *
  3. Some Ether. This can be requested from the 40 | * Rinkeby Faucet
    4. 41 | *
42 | * 43 | *

For further background information, refer to the project README. 44 | */ 45 | public class Application { 46 | 47 | private static final Logger log = LoggerFactory.getLogger(Application.class); 48 | 49 | public static void main(String[] args) throws Exception { 50 | new Application().run(); 51 | } 52 | 53 | private void run() throws Exception { 54 | 55 | // We start by creating a new web3j instance to connect to remote nodes on the network. 56 | // Note: if using web3j Android, use Web3jFactory.build(... 57 | Web3j web3j = Web3j.build(new HttpService( 58 | "https://rinkeby.infura.io/")); // FIXME: Enter your Infura token here; 59 | log.info("Connected to Ethereum client version: " 60 | + web3j.web3ClientVersion().send().getWeb3ClientVersion()); 61 | 62 | // We then need to load our Ethereum wallet file 63 | // FIXME: Generate a new wallet file using the web3j command line tools https://docs.web3j.io/command_line.html 64 | Credentials credentials = 65 | WalletUtils.loadCredentials( 66 | "", 67 | "/path/to/"); 68 | log.info("Credentials loaded"); 69 | 70 | // FIXME: Request some Ether for the Rinkeby test network at https://www.rinkeby.io/#faucet 71 | log.info("Sending 1 Wei (" 72 | + Convert.fromWei("1", Convert.Unit.ETHER).toPlainString() + " Ether)"); 73 | TransactionReceipt transferReceipt = Transfer.sendFunds( 74 | web3j, credentials, 75 | "0x19e03255f667bdfd50a32722df860b1eeaf4d635", // you can put any address here 76 | BigDecimal.ONE, Convert.Unit.WEI) // 1 wei = 10^-18 Ether 77 | .send(); 78 | log.info("Transaction complete, view it at https://rinkeby.etherscan.io/tx/" 79 | + transferReceipt.getTransactionHash()); 80 | 81 | // Now lets deploy a smart contract 82 | log.info("Deploying smart contract"); 83 | ContractGasProvider contractGasProvider = new DefaultGasProvider(); 84 | Greeter contract = Greeter.deploy( 85 | web3j, 86 | credentials, 87 | contractGasProvider, 88 | "test" 89 | ).send(); 90 | 91 | String contractAddress = contract.getContractAddress(); 92 | log.info("Smart contract deployed to address " + contractAddress); 93 | log.info("View contract at https://rinkeby.etherscan.io/address/" + contractAddress); 94 | 95 | log.info("Value stored in remote smart contract: " + contract.greet().send()); 96 | 97 | // Lets modify the value in our smart contract 98 | TransactionReceipt transactionReceipt = contract.newGreeting("Well hello again").send(); 99 | 100 | log.info("New value stored in remote smart contract: " + contract.greet().send()); 101 | 102 | // Events enable us to log specific events happening during the execution of our smart 103 | // contract to the blockchain. Index events cannot be logged in their entirety. 104 | // For Strings and arrays, the hash of values is provided, not the original value. 105 | // For further information, refer to https://docs.web3j.io/filters.html#filters-and-events 106 | for (Greeter.ModifiedEventResponse event : contract.getModifiedEvents(transactionReceipt)) { 107 | log.info("Modify event fired, previous value: " + event.oldGreeting 108 | + ", new value: " + event.newGreeting); 109 | log.info("Indexed event previous value: " + Numeric.toHexString(event.oldGreetingIdx) 110 | + ", new value: " + Numeric.toHexString(event.newGreetingIdx)); 111 | } 112 | } 113 | } 114 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | Apache License 2 | Version 2.0, January 2004 3 | http://www.apache.org/licenses/ 4 | 5 | TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 6 | 7 | 1. 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