web3j使用方法总结

分享web3j使用教程，包括转账，查询以及合约调用

简介

Web3j 是一个轻量级的 Java 库，用于与以太坊区块链交互。支持以下功能：

创建和管理以太坊钱包。
发送交易和查询区块链数据。
部署和调用智能合约。
监听事件和过滤器。

环境准备

在 pom.xml 中添加 Maven 依赖：


<dependency>
    <groupId>org.web3j</groupId>
    <artifactId>core</artifactId>
    <version>4.8.7</version>
</dependency>

基础使用

连接到以太坊节点

// 使用 Infura 节点
Web3j web3j = Web3j.build(new HttpService("https://mainnet.infura.io/v3/YOUR_API_KEY"));

// 本地节点
Web3j web3j = Web3j.build(new HttpService("http://localhost:8545"));

区块相关

// 获取当前区块高度
public BigInteger getBlockNumber() throws Exception {
    return this.w3.ethBlockNumber().send().getBlockNumber();
}

// 获取指定区块高度的区块信息
public Block getBlockByNumber(BigInteger blockNumber) throws Exception {
    return this.w3.ethGetBlockByNumber(DefaultBlockParameter.valueOf(blockNumber), true).send().getBlock();
}

// 获取指定区块高度的区块时间戳
public BigInteger getBlockTimestamp(BigInteger blockNumber) throws Exception {
    return this.getBlockByNumber(blockNumber).getTimestamp();
}

// 获取指定区块哈希的区块信息
public Block getBlockByHash(String blockHash) throws Exception {
    return this.w3.ethGetBlockByHash(blockHash, true).send().getBlock();
}

账户相关


// 获取账户余额
public BigInteger getBalance(String address) throws Exception {
    return this.w3.ethGetBalance(address, DefaultBlockParameterName.LATEST).send().getBalance();
}

// 获取账户下一个交易Nonce
public BigInteger getAddressNextNonce(String address) throws Exception {
    return this.w3.ethGetTransactionCount(address, DefaultBlockParameterName.PENDING).send().getTransactionCount();
}

交易相关


// 获取指定区块高度的所有交易信息
public List<Transaction> getTransactionsByBlockNumber(BigInteger blockNumber) throws Exception {
    List<Transaction> txs = new ArrayList<>();
    Block block = this.w3.ethGetBlockByNumber(DefaultBlockParameter.valueOf(blockNumber), true).send().getBlock();
    if (block == null) {
        return null;
    }
    for (TransactionResult<Transaction> tx : block.getTransactions()) {
        Transaction t = tx.get();
        txs.add(t);
    }
    return txs;
}

// 获取指定交易哈希的交易信息
public Transaction getTransactionByHash(String transactionHash) throws Exception {
    return this.w3.ethGetTransactionByHash(transactionHash).send().getTransaction().get();
}

// 获取指定交易哈希的交易日志信息
public Optional<TransactionReceipt> getTransactionReceipt(String transactionHash) throws Exception {
    return this.w3.ethGetTransactionReceipt(transactionHash).send().getTransactionReceipt();
}

代币转账

/*
 * 发送转账交易
 * @param from发送方私钥
 * @param to 接收方钱包地址
 * @param value 转账金额
 * */
public String ethSendTransaction(String privateKey, String to, BigInteger value) throws Exception {
    // 1.构建交易信息
    ECKeyPair ecKeyPair = ECKeyPair.create(new BigInteger(privateKey, 16));
    String address = Keys.toChecksumAddress(Keys.getAddress(ecKeyPair));

    BigInteger nonce = this.getAddressNextNonce(address);
    BigInteger gasPrice = this.getGasPrice();
    BigInteger gasLimit = BigInteger.valueOf(21000);    // 可以根据实际情况调整
    RawTransaction rawTransaction = RawTransaction.createEtherTransaction(nonce, gasPrice, gasLimit, to, value);


    // 2.签名交易
    Credentials credentials = Credentials.create(ecKeyPair);

    byte[] signedMessage = TransactionEncoder.signMessage(rawTransaction, credentials);
    String signedTx = Numeric.toHexString(signedMessage);

    // 3.发送交易
    EthSendTransaction transaction = this.w3.ethSendRawTransaction(signedTx).send();
    return transaction.getTransactionHash();
}

合约交互

需要转准备已经部署好的合约，并知道合约相关函数以及事件信息
需要了解solidity相关知识

合约代码示例

pragma solidity ^0.5.0;  //指定编译器版本
 
contract DemoStudy {    //合约名称
    uint256 public myNumber;

    // 构造函数,init data
    constructor() public {
        myNumber = 10;
    }

    function setNumber0(uint256 number) public  {
        myNumber = number;
    }

    event NumberSet1(uint256 number); // 事件
    function setNumber1(uint256 number) public  {
        myNumber = number;
        emit NumberSet1(number); //触发事件
    }

    // 抛出的事件中有index下标
    event NumberSet2(uint256 indexed number); 
    function setNumber2(uint256 number) public  {
        myNumber = number;
        emit NumberSet1(number);
        emit NumberSet2(number);
    }

    // 抛出多个参数
    event NumberSet3(uint256 number,address user); 
    function setNumber3(uint256 number) public returns (bool) {
        myNumber = number;
        emit NumberSet1(number);
        emit NumberSet2(number);
        emit NumberSet3(number,msg.sender);
        return true;
    }

    function getNumber() public view returns (uint256) {
        return myNumber;
    }
}

call合约方法

零地址调用

/*
 * 合约调用
 * @param functionName 合约方法名
 * @param contractAddress 合约地址
 * @param functionArguments 合约方法参数
 * */
public String ethCall(String functionName, String contractAddress, Type... functionArguments) throws Exception {

    // 1.编码input data信息
    List<Type> argumentList = new ArrayList<>(Arrays.asList(functionArguments));
    Function functionCall = new Function(functionName, argumentList, Collections.<TypeReference<?>>emptyList());
    String functionEncoder = FunctionEncoder.encode(functionCall);

    org.web3j.protocol.core.methods.request.Transaction requestTransaction = new org.web3j.protocol.core.methods.request.Transaction(EthConstant.BLACK_HOLE_ADDRESS, BigInteger.ZERO, BigInteger.ZERO, EthConstant.DEFAULT_GAS_LIMIT, contractAddress, BigInteger.ZERO, functionEncoder);

    // 2.调用合约方法
    EthCall ethCall = this.w3.ethCall(requestTransaction, DefaultBlockParameterName.LATEST).send();

    // 3.调用失败返回
    if (ethCall.isReverted()) {
        throw new Exception("Call contract revert! Reason: " + ethCall.getRevertReason());
    }

    // 4.返回调用结果
    return ethCall.getValue();
    
// 调用getNumber()方法示例
er.ethCall("getNumber","ContractAddress");

// 调用setNumber0()方法示例
Type[] setNumberParam = {
        new Uint256(BigInteger.valueOf(123))
};
er.ethCall("setNumber0","ContractAddress",setNumberParam);
}

指定账户调用

/*
 * 合约调用
 * @param privateKey 发送方私钥
 * @param functionName 合约方法名
 * @param contractAddress 合约地址
 * @param functionArguments 合约方法参数
 * */
public String ethCall(String privateKey, String functionName, String contractAddress, Type... functionArguments) throws Exception {

    // 1.构建交易信息
    ECKeyPair ecKeyPair = ECKeyPair.create(new BigInteger(privateKey, 16));
    String address = Keys.toChecksumAddress(Keys.getAddress(ecKeyPair));

    BigInteger nonce = this.getAddressNextNonce(address);
    BigInteger gasPrice = this.getGasPrice();
    BigInteger gasLimit = BigInteger.valueOf(21000);    // 可以根据实际情况调整

    // 2.编码input data信息
    List<Type> argumentList = new ArrayList<>(Arrays.asList(functionArguments));
    Function functionCall = new Function(functionName, argumentList, Collections.<TypeReference<?>>emptyList());
    String functionEncoder = FunctionEncoder.encode(functionCall);


    org.web3j.protocol.core.methods.request.Transaction requestTransaction =
            new org.web3j.protocol.core.methods.request.Transaction(address, nonce, gasPrice, gasLimit, contractAddress, BigInteger.ZERO, functionEncoder);


    // 3.调用合约方法
    EthCall ethCall = this.w3.ethCall(requestTransaction, DefaultBlockParameterName.LATEST).send();


    // 4.调用失败返回
    if (ethCall.isReverted()) {
        throw new Exception("Call contract revert! Reason: " + ethCall.getRevertReason());
    }

    // 5.返回调用结果
    return ethCall.getValue();
}

调用合约方法

/*
 * 合约调用
 * @param privateKey 发送方私钥
 * @param functionName 合约方法名
 * @param contractAddress 合约地址
 * @param functionArguments 合约方法参数
 * */
public String sendCallContractRawTransaction(String privateKey, String contractAddress, String functionName, Type... functionArguments) throws Exception {
    // 1.构建交易信息
    ECKeyPair ecKeyPair = ECKeyPair.create(new BigInteger(privateKey, 16));
    String address = Keys.toChecksumAddress(Keys.getAddress(ecKeyPair));

    BigInteger nonce = this.getAddressNextNonce(address);
    BigInteger gasPrice = this.getGasPrice();
    BigInteger gasLimit = BigInteger.valueOf(21000);    // 可以根据实际情况调整
    
    // 2.编码input data信息
    List<Type> argumentList = new ArrayList<>(Arrays.asList(functionArguments));
    Function functionCall = new Function(functionName, argumentList, Collections.<TypeReference<?>>emptyList());
    String functionEncoder = FunctionEncoder.encode(functionCall);
    RawTransaction rawTransaction = RawTransaction.createTransaction(nonce, gasPrice, gasLimit, contractAddress, BigInteger.ZERO, functionEncoder);


    // 3.签名交易
    Credentials credentials = Credentials.create(ecKeyPair);

    byte[] signedMessage = TransactionEncoder.signMessage(rawTransaction, credentials);
    String signedTx = Numeric.toHexString(signedMessage);

    // 4.call合约，(可忽略此步骤)
    Transaction requestTransaction =
            new Transaction(address, nonce, gasPrice, gasLimit, contractAddress, BigInteger.ZERO, functionEncoder);
    EthCall ethCall = this.w3.ethCall(requestTransaction, DefaultBlockParameterName.LATEST).send();
    if (ethCall.isReverted()) {
        throw new Exception("Call contract revert! Reason: " + ethCall.getRevertReason());
    }
    
    // 5.发送交易
    EthSendTransaction transaction = this.w3.ethSendRawTransaction(signedTx).send();
    return transaction.getTransactionHash();
}

强烈建议在发送交易之前先call一下合约方法，防止因参数有误或者合约执行失败而造成的gas浪费

监听功能

创建日志过滤器

创建一个过滤器，用于监听符合特定条件的合约事件日志, 返回一个过滤器ID。

topic说明：对合约方法调用后抛出事件的keccak256的hash。

keccak256(NumberSet1(uint256 number)) = 0x9283ff3607e3da47fe0733402e95abd90472527fbbac5a26edffcbd508134773

/*
 * 创建日志过滤器
 * @param blockStart 开始区块
 * @param blockEnd 结束区块
 * @param contractAddress 合约地址
 * @param topics 事件的topic
 * @return BigInteger filetrId
 * */
public BigInteger createFilter(BigInteger blockStart, BigInteger blockEnd, String contractAddress, String... topics) throws Exception {
    EthFilter requestEthFilter = new EthFilter(DefaultBlockParameter.valueOf(blockStart), DefaultBlockParameter.valueOf(blockEnd), contractAddress);
    requestEthFilter = requestEthFilter.addOptionalTopics(topics);
    return this.w3.ethNewFilter(requestEthFilter).send().getFilterId();
}

获取过滤器日志


/*
 * 获取过滤器的所有日志
 * @param filterId 过滤器ID
 * */
public List<Log> getFilterLogs(BigInteger filterId) throws Exception {
    List<Log> logs = new ArrayList<>();
    EthLog ethLog = this.w3.ethGetFilterLogs(filterId).send();
    for (LogResult<Log> log : ethLog.getLogs()) {
        Log l = log.get();
        logs.add(l);
    }
    return logs;
}

/*
 * 获取过滤器的增量日志
 * @param filterId 过滤器ID
 * */
public List<Log> getFilterChanges(BigInteger filterId) throws Exception {
    List<Log> logs = new ArrayList<>();
    EthLog ethLog =  this.w3.ethGetFilterChanges(filterId).send();
    for (LogResult<Log> log : ethLog.getLogs()) {
        Log l = log.get();
        logs.add(l);
    }
    return logs;
}

直接查询日志

/*
 * 创建日志过滤器
 * @param blockStart 开始区块
 * @param blockEnd 结束区块
 * @param contractAddress 合约地址
 * @param topics 事件的topic
 * */
public List<Log> getLogs(BigInteger blockStart, BigInteger blockEnd, String contractAddress,String... topics) throws Exception {

    EthFilter filter = new EthFilter(
            DefaultBlockParameter.valueOf(blockStart),
            DefaultBlockParameter.valueOf(blockEnd),
            contractAddress
    );
    filter.addOptionalTopics(topics);

    List<Log> logs = new ArrayList<>();
    EthLog ethLog = this.w3.ethGetLogs(filter).send();
    for (LogResult<Log> log : ethLog.getLogs()) {
        Log l = log.get();
        logs.add(l);
    }
    return logs;
}

参考资料

区块链

#区块链开发

web3j使用方法总结

https://zhyyao.me/2024/10/13/experience/web3j-use/

作者

zhyyao

发布于

2024年10月13日

许可协议

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