ERC20代币转账以及余额查询--java(web3j)

深藏阁楼爱情的钟 2022-01-22 04:53 1121阅读 0赞

## ERC20代币转账以及余额查询–java(web3j) ##

**准备工作**：转账之前你得有一个ERC20代币，[代币发行戳这里][Link 1]，可以在测试网上进行测试。  
因为发行代币本质就是部署智能合约，是需要消耗gas的，代币转账也是需要消耗eth作为手续费的。  
准备工作完成之后，就让我们直接进行ERC20代币转账吧～  
通过调用**web3j**的API完成相关操作，所需maven依赖：

**一：代币转账**

该代币转账是通过构建原始交易的方式进行的，请看代码，**主网亲测有效**～

/**
         * erc20代币转账
         *
         * @param from            转账地址
         * @param to              收款地址
         * @param value           转账金额
         * @param privateKey      转账这私钥
         * @param contractAddress 代币合约地址
         * @return 交易哈希
         * @throws ExecutionException
         * @throws InterruptedException
         * @throws IOException
         */
        public static String transferERC20Token(String from, String to, BigInteger value, String privateKey, String contractAddress) throws ExecutionException, InterruptedException, IOException {
            Web3j web3j = Web3j.build(new HttpService("https://mainnet.infura.io/v3/c313bf2c97834ee29d933a996caaafb0"));
            //加载转账所需的凭证，用私钥
            Credentials credentials = Credentials.create(privateKey);
            //获取nonce，交易笔数
            BigInteger nonce;
            EthGetTransactionCount ethGetTransactionCount = web3j.ethGetTransactionCount(from, DefaultBlockParameterName.PENDING).send();
            if (ethGetTransactionCount == null) {
                return null;
            }
            nonce = ethGetTransactionCount.getTransactionCount();
            //gasPrice和gasLimit 都可以手动设置
            BigInteger gasPrice;
            EthGasPrice ethGasPrice = web3j.ethGasPrice().sendAsync().get();
            if (ethGasPrice == null) {
                return null;
            }
            gasPrice = ethGasPrice.getGasPrice();
            //BigInteger.valueOf(4300000L) 如果交易失败 很可能是手续费的设置问题
            BigInteger gasLimit = BigInteger.valueOf(60000L);
            //ERC20代币合约方法
            value = value.multiply(VALUE);
            Function function = new Function(
                    TRANSFER,
                    Arrays.asList(new Address(to), new Uint256(value)),
                    Collections.singletonList(new TypeReference<Type>() {
                    }));
            //创建RawTransaction交易对象
            String encodedFunction = FunctionEncoder.encode(function);
            RawTransaction rawTransaction = RawTransaction.createTransaction(nonce, gasPrice, gasLimit,
                    contractAddress, encodedFunction);
    
            //签名Transaction
            byte[] signMessage = TransactionEncoder.signMessage(rawTransaction, credentials);
            String hexValue = Numeric.toHexString(signMessage);
            //发送交易
            EthSendTransaction ethSendTransaction = web3j.ethSendRawTransaction(hexValue).sendAsync().get();
            String hash = ethSendTransaction.getTransactionHash();
            if (hash != null) {
                return hash;
            }
            return null;
        }

**二：代币余额查询**

private static final String DATA_PREFIX = "0x70a08231000000000000000000000000";
    public static BigDecimal getBalance(String address, String contractAddress) throws IOException {
            String value = Admin.build(new HttpService("https://mainnet.infura.io"))
                    .ethCall(org.web3j.protocol.core.methods.request.Transaction.createEthCallTransaction(address,
                    contractAddress, DATA_PREFIX + address.substring(2)), DefaultBlockParameterName.PENDING).send().getValue();
            String s = new BigInteger(value.substring(2), 16).toString();
            BigDecimal balance = new BigDecimal(s).divide(WEI, 6, RoundingMode.HALF_DOWN);
            return balance;
        }

以上代码主网发行的代币亲测有效，如果对您有帮助，就点个赞吧～

最后，附上简单的ERC20代币合约

pragma solidity ^0.4.25;
    
    contract ERC20Interface {
    
        string public constant name = "测试币";
        string public constant symbol = "CSB";
        uint8 public constant decimals = 18;
    
        function totalSupply() public constant returns (uint);
        function balanceOf(address tokenOwner) public constant returns (uint balance);
        function transfer(address to, uint tokens) public returns (bool success);
        function approve(address spender, uint tokens) public returns (bool success);
        function transferFrom(address from, address to, uint tokens) public returns (bool success);
        function allowance(address tokenOwner, address spender) public constant returns (uint remaining);
    
        event Transfer(address indexed from, address indexed to, uint tokens);
        event Approval(address indexed tokenOwner, address indexed spender, uint tokens);
    }
    
    contract SafeMath {
    
        function mul(uint256 a, uint256 b) internal pure returns (uint256 c) {
            if (a == 0) {
                return 0;
            }
            c = a * b;
            assert(c / a == b);
            return c;
        }
    
        function div(uint256 a, uint256 b) internal pure returns (uint256) {
            return a / b;
        }
    
        function sub(uint256 a, uint256 b) internal pure returns (uint256) {
            assert(b <= a);
            return a - b;
        }
    
        function add(uint256 a, uint256 b) internal pure returns (uint256 c) {
            c = a + b;
            assert(c >= a);
            return c;
        }
    }
    
    
    contract CSBToken is ERC20Interface, SafeMath {
    
      string public name;
      string public symbol;
      uint8 public decimals;
      uint256 public totalSupply;
    
    
      mapping (address => uint256) public balanceOf;
    
      mapping (address => mapping (address => uint256)) public allowanceOf;
    
       constructor() public payable {
          name = "测试币";
          symbol = "CSB";
          decimals = 18;
          totalSupply = 1000000000 * 10 ** uint256(decimals);
          balanceOf[msg.sender] = totalSupply;
       }
    
        function _transfer(address _from, address _to, uint _value) internal {
           require(_to != 0x0);
           require(balanceOf[_from] >= _value);
           require(balanceOf[_to] + _value > balanceOf[_to]);
           uint previousBalances = balanceOf[_from] + balanceOf[_to];
           balanceOf[_from] -= _value;
           balanceOf[_to] += _value;
          emit Transfer(_from, _to, _value);
           assert(balanceOf[_from] + balanceOf[_to] == previousBalances);
        }
    
        function transfer(address _to, uint256 _value) public returns (bool success) {
           _transfer(msg.sender, _to, _value);
           return true;
       }
    
        function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
           require(allowanceOf[_from][msg.sender] >= _value);
           allowanceOf[_from][msg.sender] -= _value;
           _transfer(_from, _to, _value);
           return true;
       }
    
        function approve(address _spender, uint256 _value) public returns (bool success) {
           allowanceOf[msg.sender][_spender] = _value;
          emit Approval(msg.sender, _spender, _value);
           return true;
       }
    
       function allowance(address _owner, address _spender) view public returns (uint remaining){
         return allowanceOf[_owner][_spender];
       }
    
      function totalSupply() public constant returns (uint totalsupply){
          return totalSupply;
      }
    
      function balanceOf(address tokenOwner) public constant returns(uint balance){
          return balanceOf[tokenOwner];
      }
    
    }

[Link 1]: https://blog.csdn.net/jueying7573/article/details/79624944