web3j版本：

<groupId>org.web3j</groupId> <artifactId>core</artifactId> <version>4.8.4</version>

操作：erc20转币操作

区块链网络：使用了币安BSC测试网

主代码如下： `

        public static String transferErc20(String from, String to, String value, String privateKey, String contractAddress, int decimal) {
        try {
        //转账的凭证，需要传入私钥
        Credentials credentials = Credentials.create(privateKey);
        //获取交易笔数
        BigInteger nonce;
        EthGetTransactionCount ethGetTransactionCount = web3j.ethGetTransactionCount(from,DefaultBlockParameterName.LATEST).sendAsync().get();
        if (ethGetTransactionCount == null) {
            return null;
        }
        nonce = ethGetTransactionCount.getTransactionCount();
        //手续费
        BigInteger gasPrice;
        EthGasPrice ethGasPrice = web3j.ethGasPrice().sendAsync().get();
        if (ethGasPrice == null) {
            return null;
        }
        gasPrice = ethGasPrice.getGasPrice();
        //获取最后一个区块对应gaslimit做参考
        EthBlock.Block block = web3j.ethGetBlockByNumber(DefaultBlockParameterName.LATEST, false).send().getBlock();
        Long chainId = web3j.ethChainId().send().getChainId().longValue();
        BigInteger gasLimit = block.getGasLimit();

        BigInteger val = new BigDecimal(value).multiply(new BigDecimal("10").pow(decimal)).toBigInteger();// 单位换算
        Function function = new Function(
                "transfer",
                Arrays.asList(new Address(to), new Uint256(val)),
                Collections.singletonList(new TypeReference<Type>() {
                }));
        //创建交易对象
        String encodedFunction = FunctionEncoder.encode(function);
        RawTransaction rawTransaction = RawTransaction.createTransaction(nonce, gasPrice, gasLimit,
                contractAddress, encodedFunction);

        //进行签名操作
        byte[] signMessage = TransactionEncoder.signMessage(rawTransaction,chainId, credentials);
        String hexValue = Numeric.toHexString(signMessage);
        //发起交易，广播交易！
        EthSendTransaction ethSendTransaction = web3j.ethSendRawTransaction(hexValue).sendAsync().get();
        // hash 可以通过这个查询交易状态
        String hash = ethSendTransaction.getTransactionHash();
        if (hash != null) {
            //执行业务
            System.out.printf("执行成功：" + hash);
            return hash;
        }
    } catch (Exception ex) {
        //报错应进行错误处理
        ex.printStackTrace();
    }
    return null;
}

` 报错如下：

这里尝试过手工设置了gaslimit 任意大小，仍提示exceeds block gas limit，请教如何解决，谢谢

获取gasLimit 是否有更好的方式