【web3j】智能合约

web3j对于智能合约有两种方式

1、第一种：直接使用RawTrasaction进行创建

// using a raw transaction
RawTransaction rawTransaction = RawTransaction.createContractTransaction(
        <nonce>,
        <gasPrice>,
        <gasLimit>,
        <value>,
        "0x <compiled smart contract code>");
// send...

// get contract address
EthGetTransactionReceipt transactionReceipt =
             web3j.ethGetTransactionReceipt(transactionHash).send();

if (transactionReceipt.getTransactionReceipt.isPresent()) {
    String contractAddress = transactionReceipt.get().getContractAddress();
} else {
    // try again
}

2、第二种：将合约代码转换成Java Bean。

（1）首先我们需要一份写好的智能合约。

　　

pragma solidity ^0.4.18;

// Example taken from https://www.ethereum.org/greeter, also used in
// https://github.com/ethereum/go-ethereum/wiki/Contract-Tutorial#your-first-citizen-the-greeter

contract mortal {
    /* Define variable owner of the type address*/
    address owner;

    /* this function is executed at initialization and sets the owner of the contract */
    function mortal() { owner = msg.sender; }

    /* Function to recover the funds on the contract */
    function kill() { if (msg.sender == owner) suicide(owner); }
}

contract greeter is mortal {
    /* define variable greeting of the type string */
    string greeting;

    /* this runs when the contract is executed */
    function greeter(string _greeting) public {
        greeting = _greeting;
    }

    /* main function */
    function greet() constant returns (string) {
        return greeting;
    }
}

注意：智能合约的代码是solidity写的，有关solidity语法和使用可以查询solidity官网

https://solidity.readthedocs.io/en/v0.4.21/

有可能需要FQ，请自行百度科学上网

（2）进入https://ethereum.github.io/browser-solidity/#optimize=false&version=soljson-v0.4.19+commit.c4cbbb05.js网站，此网站是在线智能合约编译网站，所以比较简便，不需要安装truffle等工具。

　　

 　　　点击图示中details按钮，会出现智能合约的ABI和BIN

　　　　

　　　　将BYTECODE中的object复制下来保存成greeter.bin，点击ABI旁边的复制按钮将其保存成greeter.abi

　　　　

　　　　　　　　进入https://github.com/web3j/web3j/releases/tag/v3.3.1网站，下载web3j-3.3.1.tar，并解压。

　　　　　　　　进入目录bin下，将greeter.bin和greeter.abi，复制到目录下，在此目录命令行执行

　　　　　　　　web3j solidity generate --javaTypes greeter.bin greeter.abi -o src/ -p com.your.organisation.name

　　　　　　　　

　　　　　　　　web3j solidity generate [--javaTypes|--solidityTypes] /path/to/<smart-contract>.bin /path/to/<smart-contract>.abi -o /path/to/src/main/java -p com.your.organisation.name

　　　　　　　　　　

　　　　　　　　-o 是源代码要放的目录，-p是包名，--javaTypes也可以选择--solidityTypes

　　　　　　生成出来Greeter.java

import org.web3j.abi.FunctionEncoder;
import org.web3j.abi.TypeReference;
import org.web3j.abi.datatypes.Function;
import org.web3j.abi.datatypes.Type;
import org.web3j.abi.datatypes.Utf8String;
import org.web3j.crypto.Credentials;
import org.web3j.protocol.Web3j;
import org.web3j.protocol.core.RemoteCall;
import org.web3j.protocol.core.methods.response.TransactionReceipt;
import org.web3j.tx.Contract;
import org.web3j.tx.TransactionManager;

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

public class Greeter extends Contract {
    private static final String BINARY = "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";

    protected Greeter(String contractAddress, Web3j web3j, Credentials credentials, BigInteger gasPrice, BigInteger gasLimit) {
        super(BINARY, contractAddress, web3j, credentials, gasPrice, gasLimit);
    }

    protected Greeter(String contractAddress, Web3j web3j, TransactionManager transactionManager, BigInteger gasPrice, BigInteger gasLimit) {
        super(BINARY, contractAddress, web3j, transactionManager, gasPrice, gasLimit);
    }

    public RemoteCall<TransactionReceipt> kill() {
        Function function = new Function(
                "kill",
                Arrays.<Type>asList(),
                Collections.<TypeReference<?>>emptyList());
        return executeRemoteCallTransaction(function);
    }

    public RemoteCall<String> greet() {
        Function function = new Function("greet",
                Arrays.<Type>asList(),
                Arrays.<TypeReference<?>>asList(new TypeReference<Utf8String>() {}));
        return executeRemoteCallSingleValueReturn(function, String.class);
    }

    public static RemoteCall<Greeter> deploy(Web3j web3j, Credentials credentials, BigInteger gasPrice, BigInteger gasLimit, String _greeting) {
        String encodedConstructor = FunctionEncoder.encodeConstructor(Arrays.<Type>asList(new org.web3j.abi.datatypes.Utf8String(_greeting)));
        return deployRemoteCall(Greeter.class, web3j, credentials, gasPrice, gasLimit, BINARY, encodedConstructor);
    }

    public static RemoteCall<Greeter> deploy(Web3j web3j, TransactionManager transactionManager, BigInteger gasPrice, BigInteger gasLimit, String _greeting) {
        String encodedConstructor = FunctionEncoder.encodeConstructor(Arrays.<Type>asList(new org.web3j.abi.datatypes.Utf8String(_greeting)));
        return deployRemoteCall(Greeter.class, web3j, transactionManager, gasPrice, gasLimit, BINARY, encodedConstructor);
    }

    public static Greeter load(String contractAddress, Web3j web3j, Credentials credentials, BigInteger gasPrice, BigInteger gasLimit) {
        return new Greeter(contractAddress, web3j, credentials, gasPrice, gasLimit);
    }

    public static Greeter load(String contractAddress, Web3j web3j, TransactionManager transactionManager, BigInteger gasPrice, BigInteger gasLimit) {
        return new Greeter(contractAddress, web3j, transactionManager, gasPrice, gasLimit);
    }
}

　　　　部署智能合约

import org.web3j.crypto.Credentials;
import org.web3j.protocol.Web3j;
import org.web3j.protocol.http.HttpService;
import org.web3j.tx.Contract;

public class SmartContractTest1 {
    public static void main(String[] args) throws Exception {
        Web3j web3j = Web3j.build(new HttpService("https://kovan.infura.io/<your-token>"));
        String ownAddress = "0xD1c82c71cC567d63Fd53D5B91dcAC6156E5B96B3";
        String toAddress = "0x6e27727bbb9f0140024a62822f013385f4194999";
        Credentials credentials = Credentials.create("xxxxxxxxxxxxxxxxxxx");
        //部署智能合约
        Greeter greeter = Greeter.deploy(web3j,credentials,Contract.GAS_PRICE,Contract.GAS_LIMIT,"zx").send();
        System.out.println(greeter.getContractAddress());
　　　　　　 //调用智能合约
        System.out.println(greeter.greet().send());

    }
}

　　　　个人意见第二种因为比较清晰