javaweb控制类的存活周期，java使用web3j链接自己智能合约
javaweb控制类的存活周期，java使用web3j链接自己智能合约运行结果如下：import Java.math.BigInteger; import java.util.Arrays; import java.util.List; import org.web3j.abi.FunctionEncoder; import org.web3j.abi.FunctionReturndecoder; import org.web3j.abi.datatypes.Function; import org.web3j.abi.datatypes.Utf8String; import org.web3j.abi.datatypes.Address; import org.web3j.abi.datatypes.generated.Uint256; import org.web3j.crypto.Credentials; import org.web3j.crypto
首先，我们要有自己的智能合约，我们使用测试网络（ropsten），还要有自己开发编号。申请如下：
地址：https://infura.io/
注册登录，创建自己的项目
注意：选择测试ropsten链，复制自己的链接 web3j需要用到。
第二步：使用solidity编译自己的智能合约（个人理解就是链上的服务器脚本），为了案例的丰富性和实用性，全方位的展示web3j调度性，我们使用留言版智能合约模板，solidity代码如下（采用了8.15编译）：
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
//声明一个结构体用于留言保持
struct Message{
string word;
address from;
string timeStr;
}
contract Test_Web3j{
Message[] public AllMsg;
//构造方法
constructor (){
}
//接受留言
Function setWord(string memory sendMsgStr string memory tStr)public returns(uint256){
AllMsg.push(Message({word:sendMsgStr from:msg.sender timeStr:tStr}));
return AllMsg.length;
}
//查询留言
function getWord() public view returns(uint256 string memory address string memory){
if(AllMsg.length==0){ //当没有留言数据时候，返回空
return (0 "" address(0) "");
}else{ //当有留言时候，返回最新的一条
uint256 indexInt=AllMsg.length-1;
Message storage thisMsg=AllMsg[indexInt];
return (AllMsg.length thisMsg.word thisMsg.from thisMsg.timeStr);
}
}
//返回总留言的条数
function getSize() public view returns(uint256){
return AllMsg.length;
}
//测试方法1
function testStr() public pure returns(String memory){
return "hello word";
}
function testInt(uint256 argInt) public pure returns(uint256){
return argInt 10;
}
}
采用remix在线版发布合约，注意浏览器中需要安装metaMask；才需要ropsten有测试币
第三步 java部分
import Java.math.BigInteger;
import java.util.Arrays;
import java.util.List;
import org.web3j.abi.FunctionEncoder;
import org.web3j.abi.FunctionReturndecoder;
import org.web3j.abi.datatypes.Function;
import org.web3j.abi.datatypes.Utf8String;
import org.web3j.abi.datatypes.Address;
import org.web3j.abi.datatypes.generated.Uint256;
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.EthCall;
import org.web3j.protocol.core.methods.response.EthGetBalance;
import org.web3j.protocol.core.methods.response.EthSendTransaction;
import org.web3j.protocol.http.HttpService;
import org.web3j.abi.datatypes.Type;
import org.web3j.abi.TypeReference;
import org.web3j.tx.Contract;
import org.web3j.utils.Convert;
import org.web3j.utils.Numeric;
public class mainCreateSolitidyJava {
public static void main(String[] args) {
try {
String url = "https://ropsten.infura.io/v3/8ac1e3ea********7a4a077c0a0745";
String contractAddress="0x954e9A986467861********F5aEa8b83cAB63B6"; //合约地址
String fromAddr="0xb4377fb04FE5aDe3C35*******0cd354308807bF"; //查询用户地址
String inputPrivateKey="4369ceac05601**************a29f2ab6a41e7c6f93f3ea55222c5d"; //该账号密钥
//查询一下自己虚拟币的数量
Web3j web3j = Web3j.build(new HttpService(url));
//第二个参数：区块的参数，建议选最新区块
EthGetBalance balance = web3j.ethGetBalance(fromAddr DefaultBlockParameterName.LATEST).send();
String blanceETH = Convert.fromWei(balance.getBalance().toString() Convert.Unit.ETHER).toPlainString();//.concat(" ether");
System.out.println("====> 拥有的以太坊币 :" blanceETH);
//测试调用方法一
try {
List input = Arrays.asList(); //输入参数
List output = Arrays.asList(new TypeReference<Utf8String>() {}); //接受返回参数
String methodName = "testStr";
Function function = new Function(methodName input output);
String data = FunctionEncoder.encode(function);
Transaction transaction = Transaction.createEthCallTransaction(fromAddr contractAddress data);
EthCall ethCall = web3j.ethCall(transaction DefaultBlockParameterName.LATEST).sendAsync().get();
List<Type> results = FunctionReturnDecoder.decode(ethCall.getValue() function.getOutputParameters());
System.out.println("==111==>" results.get(0).getValue());
}catch (Exception e){
e.printStackTrace();
}
//测试调用方法二
try {
List input = Arrays.asList(new Uint256(100));
List output = Arrays.asList(new TypeReference<Uint256>() {});
String methodName = "testInt";
Function function = new Function(methodName input output);
String data = FunctionEncoder.encode(function);
Transaction transaction = Transaction.createEthCallTransaction(fromAddr contractAddress data);
EthCall ethCall = web3j.ethCall(transaction DefaultBlockParameterName.LATEST).sendAsync().get();
List<Type> results = FunctionReturnDecoder.decode(ethCall.getValue() function.getOutputParameters());
System.out.println("==222==>" results.get(0).getValue());
}catch (Exception e){
e.printStackTrace();
}
//测试调用方法三
try {
List input = Arrays.asList(new Utf8String("第一条留言") new Utf8String("这是插入时间"));
List output = Arrays.asList(new TypeReference<Uint256>() {});
String methodName = "setWord";
Function function = new Function(methodName input output);
String encodedFunction = FunctionEncoder.encode(function);
BigInteger nonce =NormalUtil.getNonce(web3j fromAddr); //获取nonce
BigInteger gasPrice = NormalUtil.requestCurrentGasPrice(web3j); //gas数
BigInteger gasLimit = Contract.GAS_LIMIT; //限制gas数
RawTransaction rawTransaction = RawTransaction.createTransaction(nonce gasPrice gasLimit contractAddress encodedFunction);
Credentials credentials = Credentials.create(inputPrivateKey);
byte[] signMessage = TransactionEncoder.signMessage(rawTransaction credentials);
String hexValue = Numeric.toHexString(signMessage);
EthSendTransaction ethResult=web3j.ethSendRawTransaction(hexValue).sendAsync().get();
System.out.println("交易编号：" ethResult.getTransactionHash());
}catch (Exception e){
e.printStackTrace();
}
//获得总留言数量
try {
List input = Arrays.asList();
List ouput = Arrays.asList(new TypeReference<Uint256>() {});
String methodName = "getSize";
Function function = new Function(methodName input ouput);
String data = FunctionEncoder.encode(function);
Transaction transaction = Transaction.createEthCallTransaction(fromAddr contractAddress data);
EthCall ethCall = web3j.ethCall(transaction DefaultBlockParameterName.LATEST).sendAsync().get();
List<Type> results = FunctionReturnDecoder.decode(ethCall.getValue() function.getOutputParameters());
System.out.println("==333==>" results.get(0).getValue());
}catch (Exception e){
e.printStackTrace();
}
//调用自己合约地址
try {
List input = Arrays.asList();
List ouput = Arrays.asList(new TypeReference<Uint256>(){} new TypeReference<Utf8String>() {} new TypeReference<Address>() {} new TypeReference<Utf8String>() {});
String methodName = "getWord";
Function function = new Function(methodName input ouput);
String data = FunctionEncoder.encode(function);
Transaction transaction = Transaction.createEthCallTransaction(fromAddr contractAddress data);
EthCall ethCall = web3j.ethCall(transaction DefaultBlockParameterName.LATEST).sendAsync().get();
//System.out.println(ethCall.getValue());
List<Type> results = FunctionReturnDecoder.decode(ethCall.getValue() function.getOutputParameters());
System.out.println("==444==>" results.get(1).getValue());
}catch (Exception e){
e.printStackTrace();
}
}catch (Exception e){
e.printStackTrace();
}
}
}
Java部分核心难度地方：ethCall和ethSendRawTransaction区别，ethcall调用的方法是不需要gas费用，而ethSendRawTransaction需要，因此此教程中，插入留言就需要使用ethSendRawTransaction方法来调用。
运行结果如下：
