Springboot integrates web3j to call Ethereum smart contract transfer + create eth address wallet

1. Create a springboot project and introduce the jar package of web3j

<!-- web3j -->
<dependency>
    <groupId>org.web3j</groupId>
    <artifactId>web3j-spring-boot-starter</artifactId>
    <version>1.6.0</version>
</dependency>

2 、 ill 配置

client-address  can create a node by yourself, or you can go to https://infura.io/ to register to get it. The following is the client address of the test chain node.

web3j:
  client-address: https://rinkeby.infura.io/key  
  admin-client: true
  httpTimeoutSeconds: 600

3. Code dry goods

First, let's talk about web3j to create a wallet address

File file = new File( "/home/wallet" ); //Specify a directory

WalletUtils. generateNewWalletFile ("Specify the password of the wallet", file, true ); //The method returns the file name of the wallet created

As for the address, haha, you can see it in the file name, or use the method to authenticate the wallet, as follows

Credentials credentials = WalletUtils.loadCredentials ( "password", wallet file);
returnAddress = credentials.getAddress();

Let's talk about the program code for transferring a certain token between two eth addresses:

Credentials credentials = WalletUtils.loadCredentials ( "Password to Outgoing Address", wallet file);
String fromAddress = credentials.getAddress();
EthGetTransactionCount ethGetTransactionCount = web3j.ethGetTransactionCount(
        fromAddress, DefaultBlockParameterName.LATEST).sendAsync().get();
BigInteger nonce = ethGetTransactionCount.getTransactionCount();
Address address = new Address(toAddress);
Uint256 value = new Uint256(amount);
List<Type> parametersList = new ArrayList<>();
parametersList.add(address);
parametersList.add(value);
List<TypeReference<?>> outList = new ArrayList<>();
Function function = new Function("transfer", parametersList, outList);
String encodedFunction = FunctionEncoder.encode(function);
RawTransaction rawTransaction = RawTransaction.createTransaction ( nonce, Gas unit price ,
         Gas maximum quantity , contract address , encodedFunction);
 byte [] signedMessage = TransactionEncoder. signMessage (rawTransaction, credentials);
String hexValue = Numeric.toHexString(signedMessage);

EthSendTransaction ethSendTransaction = web3j .ethSendRawTransaction (hexValue) .sendAsync (). Get ();
transactionHash = ethSendTransaction.getTransactionHash();

The last thing I got is this is the txHash of the transfer. You can check the transfer status (very easy) through Json-rpc.

Json-rpc description document address: https://github.com/ethereum/wiki/wiki/JSON-RPC

There are many methods provided, try it, Sao Nian!

4. If you join a company and have its own ERC20 virtual currency, you can use this java method to transfer money, haha, if you like it, please pay attention! brother

Original, please do not reprint, thank you!