调用Alchemy执行合约转账时遇eth_sendTransaction不支持错误

调用Alchemy服务触发智能合约转账时出现错误：

[Error: Returned error: Unsupported method: eth_sendTransaction. Alchemy does not hold users' private keys.]

相关代码：

import Web3 from 'web3';
const web3 = new Web3("https://eth-goerli.g.alchemy.com/v2/YPhlCYJ_fLdms1LpSRNs1n6rfcIqGHT9");
const payDrink = (async () => {
    console.log("ethAmount");
    try{
        const contract = new web3.eth.Contract(ContractAbi,contractAddress);
        const transaction = await contract.methods.transfer().send({
            from: '0x9126de09872d12c4f6d417e2cb6061d1ad9e4708',
            value: web3.utils.toWei("0.0001", 'ether'),
        });
        const transactionReciept = await transaction.wait();
        console.log(transactionReciept);
    } catch(err){
        console.log("eee",err);
    }
})

错误截图显示上述提示信息。

Alchemy作为节点服务不托管用户私钥，因此不支持eth_sendTransaction方法——该方法要求节点代为签名并发送交易，而Alchemy没有权限处理用户私钥。

方案1：前端集成钱包（如MetaMask） #

让用户通过钱包完成签名和交易发送，无需自行管理私钥：

// 替换原web3初始化逻辑
if (window.ethereum) {
    const web3 = new Web3(window.ethereum);
    // 请求用户授权账户
    await window.ethereum.request({ method: 'eth_requestAccounts' });
    
    const payDrink = async () => {
        try{
            const contract = new web3.eth.Contract(ContractAbi,contractAddress);
            // 钱包会自动填充from字段，无需手动指定
            const transaction = await contract.methods.transfer().send({
                value: web3.utils.toWei("0.0001", 'ether'),
            });
            console.log(transaction);
        } catch(err){
            console.log("eee",err);
        }
    }
}

方案2：后端离线签名交易 #

若为后端服务，需自行管理私钥，先离线签名交易再通过Alchemy发送：

import Web3 from 'web3';
const web3 = new Web3("https://eth-goerli.g.alchemy.com/v2/YPhlCYJ_fLdms1LpSRNs1n6rfcIqGHT9");

// 注意：私钥需安全存储，禁止硬编码在代码中
const privateKey = "你的账户私钥";
const account = web3.eth.accounts.privateKeyToAccount(privateKey);

const payDrink = async () => {
    try{
        const contract = new web3.eth.Contract(ContractAbi,contractAddress);
        // 编码合约方法调用数据
        const txData = contract.methods.transfer().encodeABI();
        
        // 组装交易参数
        const txParams = {
            from: account.address,
            to: contractAddress,
            value: web3.utils.toWei("0.0001", 'ether'),
            data: txData,
            gas: await web3.eth.estimateGas({ to: contractAddress, data: txData }),
            gasPrice: await web3.eth.getGasPrice(),
            nonce: await web3.eth.getTransactionCount(account.address),
            chainId: 5 // Goerli测试网Chain ID
        };
        
        // 离线签名交易
        const signedTx = await web3.eth.accounts.signTransaction(txParams, privateKey);
        // 发送已签名的交易
        const transactionReceipt = await web3.eth.sendSignedTransaction(signedTx.rawTransaction);
        console.log(transactionReceipt);
    } catch(err){
        console.log("eee",err);
    }
}

内容的提问来源于stack exchange，提问作者Hashmi