计算合约方法的签名

通过智能合约实现

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.26;contract FunctionSelector {/*"transfer(address,uint256)"0xa9059cbb"transferFrom(address,address,uint256)"0x23b872dd*/function getSelector(string calldata _func)externalpurereturns (bytes4){return bytes4(keccak256(bytes(_func)));}
}

部署合约，然后传入对应方法的签名，执行getSelector，就可以获得输出。

通过web3j实现

@Test
public void buildErc20MethodId_transferFrom(){String from = "0x5B38Da6a701c568545dCfcB03FcB875f56beddC4";String to = "0x5B38Da6a701c568545dCfcB03FcB875f56beddC4";BigDecimal amount = BigDecimal.TEN;// 构建方法调用信息 transferFrom(address,address,uint256)String method = "transferFrom";// 构建输入参数List<Type> inputArgs = new ArrayList<>();inputArgs.add(new Address(from));inputArgs.add(new Address(to));inputArgs.add(new Uint256(Convert.toWei(amount, Convert.Unit.WEI).toBigInteger()));// 合约返回值容器List<TypeReference<?>> outputArgs = new ArrayList<>();String funcABI = FunctionEncoder.encode(new Function(method, inputArgs, outputArgs));System.out.println(funcABI);Assert.assertEquals("0x23b872dd", funcABI.substring(0, 10));}