Web3.0的主要特征是开放、隐私和去中心化。其开放体现在Web2.0所谓的生态内、生态间界限将被打破，应用之间具有高度的组合性和复合性；Web3.0内部基于不同基础设施的应用之间可以被“跨链”协议解决互联互通问题。
Web 3.0:移动互联网后下一阶段的互联网生态，主要通过区块链等技术手段，实现中心化的网络形态，模拟真实世界的感觉，实现虚拟、实现打破现实边界的互联网——区块链：是分布式节点存储数据的中心化数据结构，节点是提供计算力的计算机，是计算机或服务器，具有服务器端和客户端两种性质。
springboot使用web3进行代币交换(uniswap)：
import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.List;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.web3j.abi.FunctionEncoder;
import org.web3j.abi.TypeReference;
import org.web3j.abi.datatypes.Address;
import org.web3j.abi.datatypes.Function;
import org.web3j.abi.datatypes.StaticArray;
import org.web3j.abi.datatypes.Type;
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.methods.response.EthGasPrice;
import org.web3j.protocol.core.methods.response.EthGetTransactionCount;
import org.web3j.protocol.core.methods.response.EthGetTransactionReceipt;
import org.web3j.protocol.core.methods.response.EthSendTransaction;
import org.web3j.protocol.http.HttpService;
import org.web3j.utils.Convert;
import org.web3j.utils.Numeric;
import io.renren.common.utils.R;
import net.sf.json.JSONObject;
Service
public class Uniswap{
private static final Logger log=LoggerFactory.getLogger(Uniswap.class);
Autowired
private EthGas ethGas;
Autowired
private EthAccount ethAccount;
/**
*
*param gasLimit gaslimit
*param gasPrice gas费用
*param host链路
*param privateKey自己的私钥
*param v要兑换的对应代币的
*param contractAddress如用USDT兑换BTC，则此值是BTC的合约地址
*param amountOutMin兑换代币的最小的个数
*param sendTokenContractAddress如用USDT兑换BTC，则此值是USDT的合约地址
*param approveAddress approve合约地址，设置此值可以合约内直接确认，无需调钱包插件确认
*return
*/
public R sendContract(BigInteger gasLimit,BigInteger gasPrice,String host,String privateKey,BigDecimal v,String contractAddress,BigInteger amountOutMin,
String sendTokenContractAddress,String approveAddress){
Web3j web3j=Web3j.build(new HttpService(host));
try{
Credentials credentials=Credentials.create(privateKey);
String fromAddress=credentials.getAddress();
//获取交易次数
EthGetTransactionCount ethGetTransactionCount=ethAccount.getTradeCount(web3j,privateKey);
//错误返回
if(ethGetTransactionCount.hasError()){
return R.error(ethGetTransactionCount.getError().getMessage());
}
BigInteger nonce=ethGetTransactionCount.getTransactionCount();
//合约函数参数
List<Address>addList=new ArrayList<Address>();
addList.add(new Address(sendTokenContractAddress));
addList.add(new Address(approveAddress));
StaticArray<Address>address=new StaticArray<Address>(Address.class,addList){
};
//BigInteger amountOutMin=Numeric.toBigInt("0x8d5ff4d17003f1000");
if(gasPrice.compareTo(BigInteger.valueOf(0))!=1){//没有输入gas时查询当前链路的gas
EthGasPrice ethGasPrice=ethGas.getGasPrice(web3j);
if(ethGasPrice.hasError()){
return R.error(ethGasPrice.getError().getMessage());
}
gasPrice=ethGasPrice.getGasPrice();
}
//创建inputdata
String data=createSwapMethod(amountOutMin,address,addList.size(),new Address(fromAddress),
new Uint256(System.currentTimeMillis()/1000+300));
//EthEstimateGas ethEstimateGas=ethGas.getEthEstimateGas(web3j,fromAddress,contractAddress,data);
//if(ethEstimateGas.hasError()){
//return R.error(ethEstimateGas.getError().getMessage());
//}
//BigInteger gasLimit=BigInteger.valueOf(910000);
BigInteger value=Convert.toWei(String.valueOf(v.toString()),Convert.Unit.ETHER).toBigInteger();
RawTransaction rawTransaction=RawTransaction.createTransaction(nonce,gasPrice,gasLimit,contractAddress,
value,data);
byte[]signedMessage=TransactionEncoder.signMessage(rawTransaction,credentials);
String hexValue=Numeric.toHexString(signedMessage);
log.info("hexValue:{}",hexValue);
//发送交易
EthSendTransaction ethSendTransaction=web3j.ethSendRawTransaction(hexValue).sendAsync().get();
if(ethSendTransaction.hasError()){
return R.error(ethSendTransaction.getError().getMessage());
}
log.info("transactionHash:{}",JSONObject.fromObject(ethSendTransaction));
String transactionHash=ethSendTransaction.getTransactionHash();
log.info("transactionHash:{}",transactionHash);
EthGetTransactionReceipt ethGetTransactionReceipt=web3j.ethGetTransactionReceipt(transactionHash)
.sendAsync().get();
log.info("EthGetTransactionReceipt：{}",JSONObject.fromObject(ethGetTransactionReceipt));
if(ethGetTransactionReceipt.hasError()){
return R.error(ethGetTransactionReceipt.getError().getMessage());
}
return R.ok(transactionHash);
}catch(Exception e){
//TODO:handle exception
web3j.shutdown();
return R.error(e.getMessage());
}finally{
web3j.shutdown();
}
}
SuppressWarnings("rawtypes")
public static String createSwapMethod(BigInteger amountOutMin,StaticArray<Address>addressArray,int size,
Address to,Uint256 deadline){
List<Type>parametersList=new ArrayList<Type>();
parametersList.add(new Uint256(amountOutMin));
parametersList.add(new Uint256(128));
parametersList.add(to);
parametersList.add(deadline);
parametersList.add(new Uint256(BigInteger.valueOf(size)));
parametersList.add(addressArray);
List<TypeReference<?>>outList=new ArrayList<>();
Function function=new Function("swapExactETHForTokens",parametersList,outList);
String encodedFunction=FunctionEncoder.encode(function);
System.out.println(encodedFunction);
//函数编码不正确，先替换
return encodedFunction.replace("0x8fd067c2","0x7ff36ab5");
}
}
