springboot操作以太坊（eth），使用web3j，轉賬等

開發以太坊prc客戶端：

本次使用的是《MetaMask》錢包

1，安裝node.js

2，安裝ganache-cli，開啟本地web3j的測驗服務

安裝命令：npm install -g ganache-cli

啟動本地服務命令：ganache-cli -i 1 -h 0.0.0.0 -p 8545

啟動成功同時生成是個測驗賬號，每個賬號100eth，如圖

然后再MetaMask錢包可以通過輸入秘鑰的方式添加賬號，如圖

3.springboot部分：

匯入pom <dependency>
<groupId>org.web3j</groupId>
<artifactId>core</artifactId>
<version>5.0.0</version>
</dependency>

如果運行報錯 (okhttp3.RequestBody.create(Ljava/lang/String；Lokhttp3/MediaType；)Lokhttp3/RequestBody)則添加pom

<dependency>
<groupId>com.squareup.okhttp3</groupId>
<artifactId>okhttp</artifactId>
<version>4.3.1</version>
</dependency>

創建web3j物件：

Web3j web3 = Web3j.build(new HttpService("http://localhost:8545/"));

4，已有metamask錢包的情況，沒有metamask錢包，請先申請賬號

public static void trade(Web3j web3) {
		try {
			//根據私鑰創建身份資訊
			Credentials credentials = Credentials.create("0xa91514e0c5f1d5929b3052b756d07a0123ec5cf7b86188f4410033bdc99a85e7");
			//轉賬
			TransactionReceipt transactionReceipt = Transfer.sendFunds(
					web3, credentials, "0xb425cEA579C1c2F7A902ec1aFB5d2bEE04A611eA",
					BigDecimal.valueOf(1.0), Convert.Unit.ETHER).send();
			
			System.out.println(transactionReceipt.getBlockHash());
		} catch (IOException | CipherException e) {
			e.printStackTrace();
		} catch (InterruptedException e) {
			e.printStackTrace();
		} catch (TransactionException e) {
			e.printStackTrace();
		} catch (Exception e) {
			e.printStackTrace();
		}
		
	}
	

5，使用代碼創建錢包

創建：

public static void createWallet() {
		//存放錢包的位置，不需要檔案名，會自動生成
		String filePath = "G:/eth_wallet";
		File f = new File(filePath);
		try {//"l.1061326670"你錢包的密碼
			String fileName = WalletUtils.generateNewWalletFile("l.1061326670", f , false);
			System.out.println(fileName);
			Credentials credentials = WalletUtils.loadCredentials("l.1061326670", f);
			System.out.println(credentials.getAddress());//錢包地址
			System.out.println(credentials.getEcKeyPair().getPrivateKey());//私鑰
			System.out.println(credentials.getEcKeyPair().getPublicKey());//公鑰
		} catch (CipherException | IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (InvalidAlgorithmParameterException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (NoSuchAlgorithmException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (NoSuchProviderException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
		
	}

轉賬：

public static void tradeByOnlineWallet(Web3j web3) {
		try {
			String filePath = "G:/eth_wallet/***.json";
			File f = new File(filePath);
			Credentials credentials = WalletUtils.loadCredentials("l.1061326670", f);
			TransactionReceipt transactionReceipt = Transfer.sendFunds(
					web3, credentials, "0xb425cEA579C1c2F3A024ec1aFB5d2bEE04A611eA",
					BigDecimal.valueOf(1.0), Convert.Unit.ETHER).send();
			
			System.out.println(transactionReceipt.getBlockHash());
		} catch (IOException | CipherException e) {
			e.printStackTrace();
		} catch (InterruptedException e) {
			e.printStackTrace();
		} catch (TransactionException e) {
			e.printStackTrace();
		} catch (Exception e) {
			e.printStackTrace();
		}
		
	}