簡介
web3j是一個高度模組化，響應式的，型別安全的Java和Android庫，可以用於和以太坊網路上的節點以及智慧合約進行互動。
Web3j使你與以太坊網路進行互動，不需要額外的去寫與以太坊平臺互動的程式碼開銷。
特性
- 完整地實現了Ethereum中HTTP和IPC上的JSON-RPC客戶端API
- 支援ethereum錢包
- 可以自動生成封裝好的Java型別的智慧合約(支援Solidity和Truffle定義的格式)，可以透過Java程式碼進行合約的建立，部署，以及呼叫。
- 可以新增過濾器的響應式函式API
- 支援Ethereum Name Service(ENS)
- 支援個人建立的Ethereum網路和個人的Geth客戶端API
- 支援Alchemy和Infura，所以無需自己執行以太坊客戶端
- 支援ERC20和ERC721 Token標準
- 包括上述許多場景的全面的整合測試
- 命令列工具
- 可適配Android
- 可以透過web3j-quorm支援JP Morgan的Quorum
依賴
Web3j具有五個執行時依賴
- 響應式函式依賴RxJava
- Http連線依賴OKHttp
- JSON序列化以及反序列號依賴Jackson Core
- 加密依賴Bouncy Castle
- *nix(不適用Android)依賴Jnr-unixsocket
使用SpringBoot+Web3j搭建環境
2.1 Etherum環境
透過Web3j與以太坊進行互動前提條件是需要有Ethereum環境，搭建Ethherum環境可以透過多種方式，本文僅列出常用的兩個：
- Ganache
- Docker
新建Springboot專案
首先在https://start.spring.io/ 上面初始化一個Springboot專案，匯入Idea，或者直接在Idea上面建立。
匯入Web3j
開啟pom.xml檔案，新增以下依賴：
<!-- https://mvnrepository.com/artifact/org.web3j/core -->
<dependency>
<groupId>org.web3j</groupId>
<artifactId>web3j-spring-boot-starter</artifactId>
<version>4.0.3</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.web3j/core -->
<dependency>
<groupId>org.web3j</groupId>
<artifactId>core</artifactId>
<version>4.8.4</version>
</dependency>
<dependency>
<groupId>com.squareup.okhttp3</groupId>
<artifactId>okhttp</artifactId>
<version>4.3.1</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<!-- https://mvnrepository.com/artifact/com.google.code.gson/gson -->
<dependency>
<groupId>com.google.code.gson</groupId>
<artifactId>gson</artifactId>
<version>2.9.0</version>
</dependency>
基本配置
接下來開啟application.properties檔案，新增以下內容：
# 應用名稱
spring.application.name=ethereum-client
#訪問埠
server.port=8081
#以太坊互動地址 如果以太坊環境搭建在本地就locallhost,否則使用對應的ip地址，埠預設使用8545
web3j.client-address=http://localhost:8545
基本使用
必要的配置已完成，接下來可以與Etherum互動了。這裡列出常見的幾個功能，文章最後給出完整的程式碼。
獲取最新的區塊號
EthBlockNumber ethBlockNumber = web3j.ethBlockNumber().sendAsync().get();
BigInteger blockNumber = ethBlockNumber.getBlockNumber();
獲取所有賬戶資訊
EthAccounts ethAccounts = web3j.ethAccounts().sendAsync().get();
List<String> accounts = ethAccounts.getAccounts();
查詢Gas價格
EthGasPrice ethGasPrice = web3j.ethGasPrice().sendAsync().get();
BigInteger gasPrice = ethGasPrice.getGasPrice();
獲取ChainId
EthChainId ethChainId = web3j.ethChainId().sendAsync().get();
BigInteger chainId = ethChainId.getChainId();
獲取CoinBase
EthCoinbase ethCoinbase = web3j.ethCoinbase().sendAsync().get();
String coinBase = ethCoinbase.getAddress();
根據區塊號獲取區塊資訊
DefaultBlockParameterNumber defaultBlockParameterNumber = new DefaultBlockParameterNumber(blockNumber);
EthBlock ethBlock = web3j.ethGetBlockByNumber(defaultBlockParameterNumber,true).sendAsync().get();
EthBlock.Block block = ethBlock.getBlock();
根據區塊號獲取當前區塊所有交易資訊
DefaultBlockParameterNumber defaultBlockParameterNumber = new DefaultBlockParameterNumber(blockNumber);
EthBlock ethBlock = web3j.ethGetBlockByNumber(defaultBlockParameterNumber,true).sendAsync().get();
List<EthBlock.TransactionResult> transactionResults = ethBlock.getBlock().getTransactions();
根據交易雜湊值獲取交易資訊
EthTransaction transaction = web3j.ethGetTransactionByHash(txHash).sendAsync().get();
Optional<Transaction> optionalTransaction = transaction.getTransaction();
賬戶相關
還可以透過私鑰或者Key檔案查詢當前賬戶下的Ether餘額。
查詢Ether餘額
BigInteger blockNumber = web3j.ethBlockNumber().sendAsync().get().getBlockNumber();
DefaultBlockParameterNumber defaultBlockParameterNumber = new DefaultBlockParameterNumber(blockNumber);
//根據請求引數獲取餘額
EthGetBalance ethGetBalance = web3j.ethGetBalance(credentials.getAddress(),defaultBlockParameterNumber).sendAsync().get();
原始碼
/**
* @description 獲取區塊鏈資訊
* @author newonexd
* @date 2022/6/22 21:14
*/
@RestController
@RequestMapping("/chainInfo")
public class BlockChainInfoController {
private static final Logger logger = LoggerFactory.getLogger(BlockChainInfoController.class);
@Autowired
private Web3j web3j;
/**
* @description 獲取最新的區塊號
* @author newonexd
* @date 2022/6/22 21:11
*
* * @return BigInteger
*/
@GetMapping("/blockNumber")
public BigInteger doGetLatestBlockNumber()throws Exception{
EthBlockNumber ethBlockNumber = web3j.ethBlockNumber().sendAsync().get();
BigInteger blockNumber = ethBlockNumber.getBlockNumber();
logger.info("BlockNumber: {}",blockNumber);
return blockNumber;
}
/**
* @description 獲取所有賬戶
* @author newonexd
* @date 2022/6/22 21:11
*
* * @return List<String>
*/
@GetMapping("/accounts")
public List<String> doGetAllAccounts()throws Exception{
EthAccounts ethAccounts = web3j.ethAccounts().sendAsync().get();
List<String> accounts = ethAccounts.getAccounts();
logger.info("Accounts: {}",accounts);
return accounts;
}
/**
* @description 獲取Gas價格
* @author newonexd
* @date 2022/6/22 21:11
*
* * @return BigInteger
*/
@GetMapping("/gasPrice")
public BigInteger doGetEthGasPrice()throws Exception{
EthGasPrice ethGasPrice = web3j.ethGasPrice().sendAsync().get();
BigInteger gasPrice = ethGasPrice.getGasPrice();
logger.info("Ethereum Gas Price: {}",gasPrice);
return gasPrice;
}
/**
* @description 獲取鏈Id
* @author newonexd
* @date 2022/6/22 21:12
*
* * @return BigInteger
*/
@GetMapping("/chainId")
public BigInteger doGetChainId()throws Exception{
EthChainId ethChainId = web3j.ethChainId().sendAsync().get();
BigInteger chainId = ethChainId.getChainId();
logger.info("Ethereum Chain Id: {}",chainId);
return chainId;
}
/**
* @description 獲取CoinBase
* @author newonexd
* @date 2022/6/22 21:12
*
* * @return String
*/
@GetMapping("/coinbase")
public String doGetCoinBase()throws Exception{
EthCoinbase ethCoinbase = web3j.ethCoinbase().sendAsync().get();
String coinBase = ethCoinbase.getAddress();
logger.info("Ethereum CoinBase Address: {}",coinBase);
return coinBase;
}
/**
* @description 根據區塊號獲取區塊資訊
* @author newonexd
* @date 2022/6/22 21:12
* @param blockNumber 區塊號
* @return String
*/
@GetMapping("/getBlockInfo")
public String doGetAll(@RequestParam(value="blockNumber")Long blockNumber)throws Exception{
DefaultBlockParameterNumber defaultBlockParameterNumber = new DefaultBlockParameterNumber(blockNumber);
EthBlock ethBlock = web3j.ethGetBlockByNumber(defaultBlockParameterNumber,true).sendAsync().get();
EthBlock.Block block = ethBlock.getBlock();
Gson gson = new Gson();
String info = gson.toJson(block);
logger.info(info);
return info;
}
/**
* @description 根據區塊號獲取所有交易
* @author newonexd
* @date 2022/6/22 21:13
* @param blockNumber 區塊號
* @return String
*/
@GetMapping("/getTransactionByBlockNumber")
public String doGetTransactionInfoByBlockNumber(@RequestParam(value="blockNumber")Long blockNumber)throws Exception{
DefaultBlockParameterNumber defaultBlockParameterNumber = new DefaultBlockParameterNumber(blockNumber);
EthBlock ethBlock = web3j.ethGetBlockByNumber(defaultBlockParameterNumber,true).sendAsync().get();
List<EthBlock.TransactionResult> transactionResults = ethBlock.getBlock().getTransactions();
List<Transaction> txInfos = new ArrayList<>();
transactionResults.forEach(txInfo->{
Transaction transaction = (Transaction)txInfo;
txInfos.add(transaction);
});
Gson gson = new Gson();
String transactionInfo = gson.toJson(txInfos);
logger.info(transactionInfo);
return transactionInfo;
}
/**
* @description 根據交易雜湊值獲取交易資訊
* @author newonexd
* @date 2022/6/22 21:13
* @param txHash 交易雜湊值
* @return String
*/
@GetMapping("/getTransactionInfoByHash")
public String doGetTransactionInfoByHash(@RequestParam(value="txHash")String txHash)throws Exception{
EthTransaction transaction = web3j.ethGetTransactionByHash(txHash).sendAsync().get();
Optional<Transaction> optionalTransaction = transaction.getTransaction();
StringBuilder txInfo = new StringBuilder();
if(optionalTransaction.isPresent()){
Transaction transactionInfo = optionalTransaction.get();
Gson gson = new Gson();
txInfo.append(gson.toJson(transactionInfo));
}
logger.info(txInfo.toString());
return txInfo.toString();
}
}