Web3J로 eth transaction실행

Web3J에서 

1. rawTransaction을 이용하여 트랜잭션을 실행할 수도 있고,

RawTransaction rawTransaction  = RawTransaction.createTransaction(
        nonce,
        BigInteger.valueOf(2000000020L), //gasPrice
        BigInteger.valueOf(500000L), //gasLimit
        contractAddr,
        encodedFunction);
Credentials credentials = WalletUtils.loadCredentials("passwd1234",
        "/root/.ethereum/keystore/UTC--2018-09-14T05-50-45.788742882Z--59cb2cf3e712c4...");
byte[] signedMessage = TransactionEncoder.signMessage(rawTransaction, credentials);
String hexValue = Numeric.toHexString(signedMessage);
ethCall = web3j.ethSendRawTransaction(hexValue).sendAsync().get();

2. createFunctionCallTransaction을 이용해 트랜잭션을 실행할 수도 있다. <- 이걸 추천한다. 

단, 이 방식은 수행 하기 전에 unlock Account하는 게 정석이다. 

Web3j web3j = Web3j.build(new HttpService(web3jAddress));
List<Type> inputParameters = Arrays.asList(new Uint8(param));
List<TypeReference<?>> outputParameters = Arrays.asList(new TypeReference<Type>() {});

Function function = new Function("setValue", inputParameters, outputParameters);
String encodedFunction = FunctionEncoder.encode(function);

EthSendTransaction ethCall = null;
try {
    //Nonce
    EthGetTransactionCount ethGetTransactionCount = web3j.ethGetTransactionCount(
            fromAddr, DefaultBlockParameterName.LATEST).sendAsync().get();
    BigInteger nonce = ethGetTransactionCount.getTransactionCount();
    log.info("==NONCE:" + nonce);

    //Run
    ethCall = web3j.ethSendTransaction(
            Transaction.createFunctionCallTransaction(
                    fromAddr,
                    nonce, //or nullL
                    this.getGasPrice(), //gasPrice
                    BigInteger.valueOf(27000), //gasLimit
                    contractAddr,
                    encodedFunction)
    ).sendAsync().get();
}catch (Exception e) {
    e.printStackTrace();
}

String transactionHash = ethCall.getTransactionHash();