以太坊智能合约交互调用，web3.js，web3j两种方式实现

sunbin
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确保合约已经部署、以下操作基于合约已经部署的前提下

使用web3j与合约交互

这里使用的是maven项目，第一步要引入web3j的包

引入pom

     <dependency>
            <groupId>org.web3j</groupId>
            <artifactId>core</artifactId>
            <version>3.4.0</version>
        </dependency>

代码

Java 版本的直接上代码，也就是上述三种方式的调用

import org.junit.Test;
import org.web3j.abi.FunctionEncoder;
import org.web3j.abi.FunctionReturnDecoder;
import org.web3j.abi.TypeReference;
import org.web3j.abi.datatypes.*;
import org.web3j.crypto.Credentials;
import org.web3j.crypto.RawTransaction;
import org.web3j.crypto.TransactionEncoder;
import org.web3j.protocol.Web3j;
import org.web3j.protocol.core.DefaultBlockParameterName;
import org.web3j.protocol.core.methods.request.Transaction;
import org.web3j.protocol.core.methods.response.EthGetTransactionCount;
import org.web3j.protocol.http.HttpService;
import org.web3j.tx.gas.DefaultGasProvider;
import org.web3j.utils.Numeric;

import java.math.BigInteger;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;

public class We3jTest2 {

	public static String node = "https://rinkeby.infura.io/v3/7d00bf84530c4264969a4f0f231de8b6";
	Web3j web3j;
	Credentials credentials;
	{
		web3j = Web3j.build(new HttpService(node));
		credentials = Credentials.create("私钥");
	}

	public static final String contractAddress = "0xb19c13d0A37cDDE5c1F969a0d9BD6a50B3A11B4E";


	/**
	 * 调用合约的只读方法，无需gas
	 * @throws Exception
	 */
	@Test
	public void getName() throws Exception {
		Function function = new Function(
				"getName",
				Collections.emptyList(),
				Arrays.asList(new TypeReference<Utf8String>(){}));

		String encodedFunction = FunctionEncoder.encode(function);
		org.web3j.protocol.core.methods.response.EthCall response = web3j.ethCall(
				Transaction.createEthCallTransaction(null, contractAddress, encodedFunction),
				DefaultBlockParameterName.LATEST)
				.sendAsync().get();

		List<Type> results = FunctionReturnDecoder.decode(response.getValue(), function.getOutputParameters());
		Utf8String preValue = (Utf8String)results.get(0);
		System.out.println(preValue.getValue());
	}

	/**
	 * 需要支付gas的方法
	 * @throws Exception
	 */
	@Test
	public void setName() throws Exception {
		Function function = new Function(
				"setName",
				Arrays.asList(new Utf8String("Tom")),
				Collections.emptyList());
		BigInteger nonce = getNonce(credentials.getAddress());
		String encodedFunction = FunctionEncoder.encode(function);

		BigInteger gasLimit = new BigInteger("300000");
		RawTransaction rawTransaction = RawTransaction.createTransaction(nonce, DefaultGasProvider.GAS_PRICE,gasLimit, contractAddress, encodedFunction);

		org.web3j.protocol.core.methods.response.EthSendTransaction response =
				web3j.ethSendRawTransaction(Numeric.toHexString(TransactionEncoder.signMessage(rawTransaction, credentials)))
						.sendAsync()
						.get();

		String transactionHash = response.getTransactionHash();
		System.out.println(transactionHash);
	}

	/**
	 * 需要支付gas和value的合约方法调用
	 * @throws Exception
	 */
	@Test
	public void payETH() throws Exception {
		BigInteger nonce = getNonce(credentials.getAddress());
		Function function = new Function("payETH",
				Collections.EMPTY_LIST,
				Collections.EMPTY_LIST);

		String functionEncode = FunctionEncoder.encode(function);
		BigInteger value = new BigInteger("200");
		// 与不需要支付的value的方法调用，差别就在于多传一个eth数量的value参数
		RawTransaction rawTransaction = RawTransaction.createTransaction(nonce, DefaultGasProvider.GAS_PRICE,DefaultGasProvider.GAS_LIMIT, contractAddress, value,functionEncode);
		org.web3j.protocol.core.methods.response.EthSendTransaction response =
				web3j.ethSendRawTransaction(Numeric.toHexString(TransactionEncoder.signMessage(rawTransaction, credentials)))
						.sendAsync()
						.get();
		String transactionHash = response.getTransactionHash();
		System.out.println(transactionHash);
	}


	private BigInteger getNonce(String address) throws Exception {
		EthGetTransactionCount ethGetTransactionCount =
				web3j.ethGetTransactionCount(address, DefaultBlockParameterName.LATEST)
						.sendAsync()
						.get();
		return ethGetTransactionCount.getTransactionCount();
	}

}

   /**
	 * 根据交易地址hash查询交易数据input
	 * @throws Exception
	 */

public static void callTransaction(Web3j web3j ) throws Exception {  
        EthTransaction transaction = web3j.ethGetTransactionByHash("0xfa0716964f83e68554ec0614228a58362939e225ef37bc2d96012b5dc0471a83").sendAsync().get();  
        Optional<org.web3j.protocol.core.methods.response.Transaction> optionalTransaction = transaction.getTransaction();  
            if(optionalTransaction.isPresent()){  
                org.web3j.protocol.core.methods.response.Transaction transactionInfo = optionalTransaction.get();  
                System.out.println("交易input信息---------------"+transactionInfo.getInput());  
            }
}

总结

  1. 只读合约的调用的是call方法，这种方法无需私钥签名，只需要知道合约的地址和方法(方法名，入参、出参)即可。
  2. 支付gas以及带value的调用，都是需要账户私钥的签名，分为三个步骤：encode(方法编码)、sign (对方法签名)、send(发送签名交易)。
  3. 不管是js和java,调用流程都是一致的，本质上都是和以太坊节点通过json-rpc调用

代码

根据交易hash查询交易内容及区块信息

package com.example.demo.contract;  
  
import com.example.demo.util.Constants;  
import org.bouncycastle.util.encoders.Hex;  
import org.web3j.crypto.Credentials;  
import org.web3j.crypto.WalletUtils;  
import org.web3j.protocol.Web3j;  
import org.web3j.protocol.core.DefaultBlockParameter;  
import org.web3j.protocol.core.methods.response.EthBlock;  
import org.web3j.protocol.core.methods.response.EthTransaction;  
import org.web3j.protocol.http.HttpService;  
  
import java.math.BigInteger;  
import java.util.concurrent.ExecutionException;  
  
public class HelloWorldDeploy {  
  
public static void main(String[] args) throws Exception {  
// 启动客户端  
Web3j web3j = Web3j.build(new HttpService(Constants.URL));  
Credentials credentials = WalletUtils.loadCredentials(Constants.PASSWORD, Constants.SOURCE);  
System.out.println("getCredentialsAddress : " + credentials.getAddress());  
  
pendingTransactionFlowable(web3j);  
}  
  
/**  
* 根据交易hash查询交易信息  
*  
* @param web3j  
* @throws ExecutionException  
* @throws InterruptedException  
*/  
public static void pendingTransactionFlowable(Web3j web3j) throws ExecutionException, InterruptedException {  
  
EthTransaction ethTx = web3j.ethGetTransactionByHash("0xbf56c46fcadf382d5d8fc5c617828220ba0441912cf6020759c51f7d3961ff60").sendAsync().get();  
org.web3j.protocol.core.methods.response.Transaction tx = ethTx.getTransaction().get();  
  
System.out.println("交易input：" + tx.getInput());  
  
String input = tx.getInput();  
String decodedInput = new String(Hex.decode(input.substring(2)));  
  
// String decodedInput = new String(Hex.decode("546f6d"));  
System.out.println("解码后的input值：" + decodedInput.substring(decodedInput.indexOf("\u0003") + 1).trim());  
  
String blockHash = tx.getBlockHash();  
BigInteger blockNumber = tx.getBlockNumber();  
String from = tx.getFrom();  
String to = tx.getTo();  
BigInteger amount = tx.getValue();  
  
// 交易信息  
System.out.println("交易地址 hash ：" + tx.getHash());  
System.out.println("交易区块 ：" + blockNumber);  
System.out.println("转出 account：" + from);  
System.out.println("转入（合约） account：" + to);  
System.out.println("交易value：" + amount);  
System.out.println("交易input：" + tx.getInput());  
  
// 根据区块hash 查询区块信息  
EthBlock ethBlock = web3j.ethGetBlockByHash(blockHash, true).sendAsync().get();  
  
EthBlock.Block blockByHash = ethBlock.getBlock();  
  
System.out.println("区块hash ：" + blockHash);  
  
  
// 根据区块number 查询区块信息  
DefaultBlockParameter blockParameter = DefaultBlockParameter.valueOf(blockNumber);  
ethBlock = web3j.ethGetBlockByNumber(blockParameter, true).sendAsync().get();  
  
EthBlock.Block bk = ethBlock.getBlock();  
  
System.out.println("区块 number： " + blockNumber);  
System.out.println("区块 hash：" + bk.getHash());  
System.out.println("区块 number：" + blockByHash.getNumber());  
System.out.println("区块 parent hashes：" + blockByHash.getParentHash());  
  
  
// 根据区块 查询交易信息  
for (EthBlock.TransactionResult<?> txResult : blockByHash.getTransactions()) {  
EthBlock.TransactionObject txObject = (EthBlock.TransactionObject) txResult;  
// 交易信息  
System.out.println("转出 account：" + txObject.getFrom());  
System.out.println("转入（合约）：" + txObject.getTo());  
System.out.println("交易value：" + txObject.getValue());  
System.out.println("交易input：" + txObject.getInput());  
}  
  
  
}  
}

使用web3.js与合约交互

以下操作在node.js环境下运行

在项目中引入web3.js

npm install web3

项目骨架

	var Web3 = require('web3');
	var web3 = new Web3("https://rinkeby.infura.io/v3/7d00bf84530c4264969a4f0f231de8b6");
	var privateKey = "私钥";
	var contractAbi = [{"inputs":[],"name":"getBalance","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"getName","outputs":[{"internalType":"string","name":"","type":"string"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"name","outputs":[{"internalType":"string","name":"","type":"string"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"payETH","outputs":[],"stateMutability":"payable","type":"function"},{"inputs":[{"internalType":"string","name":"_name","type":"string"}],"name":"setName","outputs":[],"stateMutability":"nonpayable","type":"function"},{"stateMutability":"payable","type":"receive"}];
	var contractAddress = "0xb19c13d0A37cDDE5c1F969a0d9BD6a50B3A11B4E"
	var hello = new web3.eth.Contract(contractAbi, contractAddress);
	
	main()
	  .then(() => process.exit(0))
	  .catch(error => {
	    console.error(error);
	    process.exit(1);
	  });
	
	
	async function main(){
	  await getName();
	  
	}
	async function getName(){
	  var name = await hello.methods.getName().call();
	  console.log(name);
	}

只读调用

	async function getName(){
	  var name = await hello.methods.getName().call();
	  console.log(name);
	}
	
	async function getBalance(){
	  var balance = await hello.methods.getBalance().call();
	  console.log("balance = "+balance);
	}

支付gas的调用

	async function setName(){
	  var name = "Jack";
	  var functionEncode = await hello.methods.setName(name).encodeABI();
	  var sign = await web3.eth.accounts.signTransaction({
	    gas: 300000,
	    to: contractAddress,
	    data: functionEncode,
	   }, privateKey);
	   var result = await web3.eth.sendSignedTransaction(sign.rawTransaction);
	  console.log("setName txHash = "+result.transactionHash);
	}

支付gas和value的调用

	async function reviceETH(){
	   var ethValue = 100;
	   var functionEncode = await hello.methods.reviceETH().encodeABI();
	   var sign = await web3.eth.accounts.signTransaction({
	     gas: 300000, 
	     to: contractAddress,
	     data: functionEncode,
	     value: ethValue
	    }, privateKey);
	    var result = await web3.eth.sendSignedTransaction(sign.rawTransaction);
	    console.log("reviceETH resultTxHash = "+result.transactionHash);
	}

合约的etherscan地址

参考文档

web3.js 中文文档
web3j 英文文档
web3h 中文文档

上述内容如有错误欢迎留言讨论。

补充：

web3j 调用返回多个地址参数的类型（未验证）

合约返回的值是一个地址数组的情况怎么写。
如下，是我的一个例子

    @Test
	public void callContractTransaction() throws Exception {
		Function function = new Function(
				"getComponents",
				Collections.EMPTY_LIST,
				Arrays.asList(new TypeReference<DynamicArray<Address>>(){}));

		String encodedFunction = FunctionEncoder.encode(function);
		org.web3j.protocol.core.methods.response.EthCall response = web3j.ethCall(
				Transaction.createEthCallTransaction(null, contractAddress, encodedFunction),
				DefaultBlockParameterName.LATEST)
				.sendAsync().get();
		Assert.isNull(response.getError(),"callContractTransaction error");

		List<Type> results = FunctionReturnDecoder.decode(response.getValue(), function.getOutputParameters());
		for (Type result : results) {
			System.out.println(result.getValue());
		}
	}
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