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Web3j使用教程（2）_conflux.web3j

作者：我家小花儿 | 2024-04-14 01:42:15

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conflux.web3j

3.加入智能合约

首先安装solc（用于编译智能合约）和web3j命令行工具（用于打包智能合约）

npm install -g solc

web3j安装地址： Releases · web3j/web3j · GitHub，选择对应操作系统

首先准备一个智能合约 Owner.sol，建议先在remix上测试一下Remix - Ethereum IDE

  1. //SPDX-License-Identifier:UNLICENSED
  2.  
  3. pragma solidity  >=0.7.0 <0.9.0;
  4.  
  5. contract Qwner {
  6.         address private owner;
  7.         event OwnerSet(address oldAddress,address newAddress);
  8.         modifier isOwner(){
  9.             require (msg.sender==owner,"Caller is not owner!");
  10.             _;
  11.         }
  12.         constructor (){
  13.             owner = msg.sender;
  14.             emit OwnerSet( address(0) , owner);
  15.         }
  16.         function changeOwner (address newOwner) public isOwner {
  17.             emit OwnerSet(owner, newOwner);
  18.             owner = newOwner;
  19.             
  20.         }
  21.         function getOwner()public view returns (address) {
  22.             return owner;
  23.         }
  24.  
  25. }

先编译  solcjs Owner.sol --bin --abi --optimize -o .\ 然后你可以看到当前文件夹下生成了两个文件，.abi和.bin，这名字有点反人类，最好改成Owner.abi和Owner.bin

 然后打包成把合约打包成Java文件使用如下命令，其中-p是指定包名

web3j  generate solidity -a src\main\Owner.abi -b src\main\Owner.bin -o src\main\java\ -p com.example

执行完上述命令后可以看到src\main\java\com\example下多了一个Owner.java文件

 接着就是代码，包括部署智能合约，调用智能合约的函数：

  1. package com.example;
  2.  
  3. import java.io.BufferedReader;
  4. import java.io.InputStreamReader;
  5. import java.math.BigInteger;
  6. import java.util.List;
  7. import org.web3j.crypto.Credentials;
  8. import org.web3j.protocol.Web3j;
  9. import org.web3j.protocol.core.methods.response.TransactionReceipt;
  10. import org.web3j.protocol.http.HttpService;
  11. import org.web3j.tx.gas.ContractGasProvider;
  12. import org.web3j.tx.gas.DefaultGasProvider;
  13.  
  14. class Cpp{
  15.     public static void main(String[] args) {
  16.         try {
  17.             Web3j web3j = Web3j.build(new HttpService("http://127.0.0.1:8545"));
  18.             //创建钱包
  19.             Credentials defaulCredential = Credentials.create(App.privateKey1);
  20.             BigInteger gasPrice = web3j.ethGasPrice().send().getGasPrice();
  21.             //这个类的作用是你能够根据你不同函数名称灵活的选择不同的GasPrice和GasLimit
  22.             ContractGasProvider  myGasProvider = new DefaultGasProvider(){
  23.                 @Override
  24.                 public BigInteger getGasPrice(String contractFunc ) {
  25.                     return gasPrice;
  26.                 }
  27.                 @Override
  28.                 public BigInteger getGasLimit(String contractFunc ){
  29.                     return BigInteger.valueOf(6721975);
  30.                 }
  31.             };    
  32.             //部署合约，并打印合约地址
  33.             Owner myContract = Owner.deploy(web3j, defaulCredential, myGasProvider).send();
  34.             System.out.println("deploy contract: "+myContract.isValid());
  35.             System.out.println("contract adddress: "+myContract.getContractAddress());
  36.         } catch (Exception e) {
  37.             e.printStackTrace();
  38.         }
  39.         
  40.     }
  41. }
  42. public class App 
  43. {
  44.     static Web3j web3j = null;
  45.     //ganache上的accounts[0]和accounts[1]的私钥
  46.     static String privateKey1 = "0x64685c9589ef1e937e8009eba589059d4b7b10bb44a6efc6eeb436c7f47ab85c";
  47.     static String privateKey2 = "0xae7d780682ee82c5301152bec4ddb51ada56944135d211130a582f33c52d7c1d";
  48.     //硬编码，填入合约部署后输出的合约地址
  49.     static String contractAddress = "0x30a856cd0aaf589b99152331ae4bc1193ed32570";
  50.  
  51.     public static void main(String[] args )
  52.     {
  53.         try {
  54.             web3j = Web3j.build(new HttpService("http://127.0.0.1:8545"));
  55.             String clientVersion = web3j.web3ClientVersion().send().getWeb3ClientVersion();
  56.             System.out.println("clientVersion : "+clientVersion);
  57.             List<String> accounts = web3j.ethAccounts().send().getAccounts(); 
  58.             System.out.println("accounts"+accounts);
  59.             //连个私钥accounts[0]和accounts[1]
  60.             Credentials defaulCredential = Credentials.create(privateKey1);
  61.             Credentials secondCredentials = Credentials.create(privateKey2);
  62.             BigInteger gasPrice = web3j.ethGasPrice().send().getGasPrice();
  63.             ContractGasProvider  myGasProvider = new DefaultGasProvider(){
  64.                 @Override
  65.                 public BigInteger getGasPrice(String contractFunc ) {
  66.                     return gasPrice;
  67.                 }
  68.                 @Override
  69.                 public BigInteger getGasLimit(String contractFunc ){
  70.                     return BigInteger.valueOf(6721975);
  71.                 }
  72.             };
  73.             BufferedReader br = new BufferedReader( new InputStreamReader(System.in));
  74.             String command;
  75.             //根据地址获取合约实例，注意这两个合约实例不同之处在于他们的用户不同，第一个合约对应accounts[0]，第二给合约对应accounts[1]
  76.             Owner myContract = Owner.load(contractAddress, web3j,defaulCredential , myGasProvider);
  77.             Owner secondContract = Owner.load(contractAddress, web3j,secondCredentials , myGasProvider);
  78.             //判断合约是否合法，这一步也很重要
  79.             if(myContract.isValid()==false||secondContract.isValid()==false) {
  80.                 throw new Exception("load contract error");
  81.             }
  82.             System.out.println("load contract: "+myContract.isValid()+" "+secondContract.isValid());
  83.             System.out.println("contract adddress: "+myContract.getContractAddress()+"  "+secondContract.getContractAddress());
  84.              
  85.             boolean exit = false;
  86.             TransactionReceipt receipt;
  87.             while (exit == false) {
  88.                 System.out.println("please input command :");
  89.                 command = br.readLine();
  90.                 switch (command){
  91.                     case "set":{
  92.                         //accounts[0]把Owner设成accounts[1]，accounts[1]再设成accounts[0]，如此循环
  93.                         if( myContract.getOwner().send().equals( accounts.get(0) ) ){
  94.                             receipt = myContract.changeOwner(accounts.get(1)).send();          
  95.                         }
  96.                         else {
  97.                             receipt = secondContract.changeOwner(accounts.get(0)).send();                         
  98.                         }
  99.                         System.out.println(receipt);
  100.                         System.out.println("now owner is ");
  101.                         System.out.println(myContract.getOwner().send());
  102.                         
  103.                         break;
  104.                     }
  105.                     case "get":{
  106.                         System.out.println("now owner is ");
  107.                         System.out.println(myContract.getOwner().send());
  108.                         break;
  109.                     }
  110.                     case "exit": {
  111.                         System.out.println("you type exit");
  112.                         exit = true;
  113.                         break;
  114.                     }
  115.                     default :{
  116.                         System.out.println("wrong command input again");
  117.                         break;
  118.                     }
  119.                 }
  120.             }                      
  121.         } catch (Exception e) {
  122.             System.err.println(e);
  123.         }
  124.     }
  125. }
  126.

部署合约（Cpp中main函数输出）

加载合约并调用合约函数 （App中main函数输出）

4.事件监听 

还能监听区块链事件，主要有三种：监听区块，监听交易，监听合约事件

  1. package com.example;
  2.  
  3. import java.io.BufferedReader;
  4. import java.io.InputStreamReader;
  5. import java.math.BigInteger;
  6.  
  7. import org.web3j.crypto.Credentials;
  8. import org.web3j.protocol.Web3j;
  9. import org.web3j.protocol.core.DefaultBlockParameterName;
  10. import org.web3j.protocol.http.HttpService;
  11. import org.web3j.tx.gas.ContractGasProvider;
  12. import org.web3j.tx.gas.DefaultGasProvider;
  13.  
  14. import io.reactivex.disposables.CompositeDisposable;
  15. import io.reactivex.disposables.Disposable;
  16.  
  17. public class App 
  18. {
  19.     static Web3j web3j = Web3j.build(new HttpService("http://127.0.0.1:8545"));
  20.     static String privateKey = "0x36308cc80ca2e632b0fb90d8acbe316d4c23f782f03131d4406a0026ed5de9e7";
  21.     static String contractAddress = "0x30a856cd0aaf589b99152331ae4bc1193ed32570";
  22.     static DefaultBlockParameterName earliest = DefaultBlockParameterName.EARLIEST;
  23.     static DefaultBlockParameterName latest = DefaultBlockParameterName.LATEST;
  24.     public static void main( String[] args )
  25.     {
  26.         try {
  27.             String clientVersion = web3j.web3ClientVersion().send().getWeb3ClientVersion();
  28.             System.out.println(clientVersion);
  29.             Credentials defaulCredential = Credentials.create(privateKey);
  30.             BigInteger gasLimit = BigInteger.valueOf(6721975);
  31.             BigInteger gasPrice = web3j.ethGasPrice().send().getGasPrice();
  32.             ContractGasProvider simplProvider = new DefaultGasProvider(){
  33.                 @Override
  34.                 public BigInteger getGasPrice(String contractFunc ) {
  35.                     return gasPrice;
  36.                 }
  37.                 @Override
  38.                 public BigInteger getGasLimit(String contractFunc ){
  39.                     return gasLimit;
  40.                 }
  41.             };
  42.             Owner mycontract = Owner.load(contractAddress, web3j, defaulCredential, simplProvider);
  43.             if(mycontract.isValid()==false){
  44.                 throw new Exception("load error");
  45.             }
  46.             System.out.println("load contract: "+mycontract.isValid());
  47.  
  48.             //使用CompositeDisposable
  49.             CompositeDisposable disposableSet = new CompositeDisposable();
  50.             //监听区块
  51.             Disposable blockSubscription  =web3j.blockFlowable(false).subscribe( block -> {
  52.                 System.out.println("new block: "+block.getBlock().getHash());
  53.             } );
  54.             //监听交易
  55.             Disposable txsubcription = web3j.transactionFlowable().subscribe( tx -> {
  56.                 System.out.println("new tx: from "+tx.getFrom()+ "; to "+tx.getTo());
  57.             } );
  58.             //监听合约的OwnerSet事件
  59.             Disposable ownersetSubscription = mycontract.ownerSetEventFlowable(latest, latest).subscribe(res -> {
  60.                 System.out.println(res.log);
  61.                 System.out.println("owner chage: old "+res.oldAddress+" new "+res.newAddress);
  62.             });
  63.             
  64.             disposableSet.add(blockSubscription);
  65.             disposableSet.add(txsubcription);
  66.             disposableSet.add(ownersetSubscription);
  67.             System.out.println(disposableSet);
  68.             BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
  69.             String command =null;
  70.             while(true){
  71.                 System.out.println("input command: ");
  72.                 command = br.readLine();
  73.                 if(command.equals("stop")){
  74.                     disposableSet.dispose();
  75.                     System.out.println(disposableSet);
  76.                     break;
  77.                 } else {
  78.                     continue;
  79.                 }
  80.             }
  81.         } catch (Exception e) {
  82.             System.err.println(e);
  83.         }
  84.     }
  85. }

控制台输出： 

 

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