前面我们学习了部署以太坊合约,我们的操作都是在钱包中完成的。

然而当我们面对我们的用户时我们不可能说叫他们安装钱包,然后学习这些复杂操作。

对于普通的用户来说,这太不友好了,那么我们就得继续封装,允许用户在我们的网站或者手机上动动手指就可以完成简单的操作。

下面我们就学习一下如何用代码的方式替代钱包里的操作来调用智能合约。

我们重点讲一下两种访问智能合约方式: web3.jsweb3j

web3.js方式

如果你还没有安装node js 安装,请先安装node js,此处不再赘述。

安装

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npm install web3

代码

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var Web3 = require('web3');
web3 = new Web3(new Web3.providers.HttpProvider("http://localhost:8545"));
var abi = [ { "constant": false, "inputs": [ { "name": "newSellPrice", "type": "uint256" }, { "name": "newBuyPrice", "type": "uint256" } ], "name": "setPrices", "outputs": [], "payable": false, "stateMutability": "nonpayable", "type": "function" }, { "constant": true, "inputs": [], "name": "name", "outputs": [ { "name": "", "type": "string", "value": "CoolCoin" } ], "payable": false, "stateMutability": "view", "type": "function" }, { "constant": false, "inputs": [ { "name": "_spender", "type": "address" }, { "name": "_value", "type": "uint256" } ], "name": "approve", "outputs": [ { "name": "success", "type": "bool" } ], "payable": false, "stateMutability": "nonpayable", "type": "function" }, { "constant": true, "inputs": [], "name": "totalSupply", "outputs": [ { "name": "", "type": "uint256", "value": "1.009e+22" } ], "payable": false, "stateMutability": "view", "type": "function" }, { "constant": false, "inputs": [ { "name": "_from", "type": "address" }, { "name": "_to", "type": "address" }, { "name": "_value", "type": "uint256" } ], "name": "transferFrom", "outputs": [ { "name": "success", "type": "bool" } ], "payable": false, "stateMutability": "nonpayable", "type": "function" }, { "constant": true, "inputs": [], "name": "decimals", "outputs": [ { "name": "", "type": "uint8", "value": "18" } ], "payable": false, "stateMutability": "view", "type": "function" }, { "constant": false, "inputs": [ { "name": "_value", "type": "uint256" } ], "name": "burn", "outputs": [ { "name": "success", "type": "bool" } ], "payable": false, "stateMutability": "nonpayable", "type": "function" }, { "constant": true, "inputs": [], "name": "sellPrice", "outputs": [ { "name": "", "type": "uint256", "value": "1" } ], "payable": false, "stateMutability": "view", "type": "function" }, { "constant": true, "inputs": [ { "name": "", "type": "address" } ], "name": "balanceOf", "outputs": [ { "name": "", "type": "uint256", "value": "0" } ], "payable": false, "stateMutability": "view", "type": "function" }, { "constant": false, "inputs": [ { "name": "target", "type": "address" }, { "name": "mintedAmount", "type": "uint256" } ], "name": "mintToken", "outputs": [], "payable": false, "stateMutability": "nonpayable", "type": "function" }, { "constant": false, "inputs": [ { "name": "_from", "type": "address" }, { "name": "_value", "type": "uint256" } ], "name": "burnFrom", "outputs": [ { "name": "success", "type": "bool" } ], "payable": false, "stateMutability": "nonpayable", "type": "function" }, { "constant": true, "inputs": [], "name": "buyPrice", "outputs": [ { "name": "", "type": "uint256", "value": "2" } ], "payable": false, "stateMutability": "view", "type": "function" }, { "constant": true, "inputs": [], "name": "owner", "outputs": [ { "name": "", "type": "address", "value": "0x914995c9c3c993c9d3fdd63602c91823f932b308" } ], "payable": false, "stateMutability": "view", "type": "function" }, { "constant": true, "inputs": [], "name": "symbol", "outputs": [ { "name": "", "type": "string", "value": "c" } ], "payable": false, "stateMutability": "view", "type": "function" }, { "constant": false, "inputs": [], "name": "buy", "outputs": [], "payable": true, "stateMutability": "payable", "type": "function" }, { "constant": false, "inputs": [ { "name": "_to", "type": "address" }, { "name": "_value", "type": "uint256" } ], "name": "transfer", "outputs": [], "payable": false, "stateMutability": "nonpayable", "type": "function" }, { "constant": true, "inputs": [ { "name": "", "type": "address" } ], "name": "frozenAccount", "outputs": [ { "name": "", "type": "bool", "value": false } ], "payable": false, "stateMutability": "view", "type": "function" }, { "constant": false, "inputs": [ { "name": "_spender", "type": "address" }, { "name": "_value", "type": "uint256" }, { "name": "_extraData", "type": "bytes" } ], "name": "approveAndCall", "outputs": [ { "name": "success", "type": "bool" } ], "payable": false, "stateMutability": "nonpayable", "type": "function" }, { "constant": true, "inputs": [ { "name": "", "type": "address" }, { "name": "", "type": "address" } ], "name": "allowance", "outputs": [ { "name": "", "type": "uint256", "value": "0" } ], "payable": false, "stateMutability": "view", "type": "function" }, { "constant": false, "inputs": [ { "name": "amount", "type": "uint256" } ], "name": "sell", "outputs": [], "payable": false, "stateMutability": "nonpayable", "type": "function" }, { "constant": false, "inputs": [ { "name": "target", "type": "address" }, { "name": "freeze", "type": "bool" } ], "name": "freezeAccount", "outputs": [], "payable": false, "stateMutability": "nonpayable", "type": "function" }, { "constant": false, "inputs": [ { "name": "newOwner", "type": "address" } ], "name": "transferOwnership", "outputs": [], "payable": false, "stateMutability": "nonpayable", "type": "function" }, { "inputs": [ { "name": "initialSupply", "type": "uint256", "index": 0, "typeShort": "uint", "bits": "256", "displayName": "initial Supply", "template": "elements_input_uint", "value": "" }, { "name": "tokenName", "type": "string", "index": 1, "typeShort": "string", "bits": "", "displayName": "token Name", "template": "elements_input_string", "value": "" }, { "name": "tokenSymbol", "type": "string", "index": 2, "typeShort": "string", "bits": "", "displayName": "token Symbol", "template": "elements_input_string", "value": "" } ], "payable": false, "stateMutability": "nonpayable", "type": "constructor" }, { "anonymous": false, "inputs": [ { "indexed": false, "name": "target", "type": "address" }, { "indexed": false, "name": "frozen", "type": "bool" } ], "name": "FrozenFunds", "type": "event" }, { "anonymous": false, "inputs": [ { "indexed": true, "name": "from", "type": "address" }, { "indexed": true, "name": "to", "type": "address" }, { "indexed": false, "name": "value", "type": "uint256" } ], "name": "Transfer", "type": "event" }, { "anonymous": false, "inputs": [ { "indexed": true, "name": "from", "type": "address" }, { "indexed": false, "name": "value", "type": "uint256" } ], "name": "Burn", "type": "event" } ];
var address = "0x63b5047Decd4501d4eb3bb7b30e3da89cE37c2f5";
var coolcoin = new web3.eth.Contract(abi);
coolcoin.options.address = address;
coolcoin.methods.balanceOf('0xc2298C3398584aaB380fafb564037D9Fb910e0a1').call({from: address}, function(error, result){
    console.log(result);
});

代码讲解

第1行代码我们引入了web3的库。

第2行代码设置服务器。

第3行代码设置ABI(Application Binary Interface): 应用程序二进制接口。这里的ABI我们可以在钱包界面,点击显示界面,复制其中的JSon格式数据即可。 里面主要订了我们合约内容。

第4行填写合约地址。

rpc

第5、6行通过abi和address获取合约。

最后我们以异步方式调用balanceOf方法,该方法使用了address来查询地址0xc2298C3398584aaB380fafb564037D9Fb910e0a1有多少个Cool Coin。

大家可以通过执行该方法对比Mist钱包查询,自行验证余额是否一致。

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node CoolCoin.js

有关 web3 更多 API可参考 : 这里

web3j方式

合约准备:

由于java的远程调用合约需要一个编译后的二进制码,利用已经存在的合约时,我暂未找到如何获取这个二进制码,所以在此我又重新发布了一个新合约才能获取编译后的二进制码。

rpc

rpc

开始

Maven

java 8:

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<dependency>
    <groupId>org.web3j</groupId>
    <artifactId>core</artifactId>
    <version>3.3.1</version>
</dependency>

CoolCoin.java

继承自Contract 并且对合约进行封装

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import org.web3j.abi.TypeReference;
import org.web3j.abi.datatypes.Function;
import org.web3j.abi.datatypes.Type;
import org.web3j.abi.datatypes.generated.Uint256;
import org.web3j.crypto.Credentials;
import org.web3j.protocol.Web3j;
import org.web3j.protocol.core.RemoteCall;
import org.web3j.tx.Contract;

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

/**
 * Created by hxchen on 2018/4/21.
 */
public class CoolCoin extends Contract{
    private static final String BINARY = "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";

    /**
     * 构造函数
     * @param contractAddress
     * @param web3j
     * @param credentials
     * @param gasPrice
     * @param gasLimit
     */
    public CoolCoin(String contractAddress, Web3j web3j, Credentials credentials, BigInteger gasPrice, BigInteger gasLimit){
        super(BINARY, contractAddress, web3j, credentials, gasPrice, gasLimit);
    }

    /**
     * 加载合约
     * @param contractAddress
     * @param web3j
     * @param credentials
     * @param gasPrice
     * @param gasLimit
     * @return
     */
    public static CoolCoin load(String contractAddress, Web3j web3j, Credentials credentials, BigInteger gasPrice, BigInteger gasLimit) {
        return new CoolCoin(contractAddress, web3j, credentials, gasPrice, gasLimit);
    }

    /**
     * 调用合约函数 balanceOf
     * @param address
     * @return
     */
    public RemoteCall balanceOf(String address){
        Function function = new Function("balanceOf",
                Arrays.<Type>asList(new org.web3j.abi.datatypes.Address(address)),
                Arrays.<TypeReference<?>>asList(new TypeReference<Uint256>() {}));
        return executeRemoteCallSingleValueReturn(function, BigInteger.class);
    }

}

CoolCoinClient.java

一个调用合约函数的测试文件

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import com.threeafun.ethereum.contract.CoolCoin;
import org.web3j.crypto.Credentials;
import org.web3j.protocol.Web3j;
import org.web3j.protocol.core.RemoteCall;
import org.web3j.protocol.http.HttpService;
import org.web3j.tx.Contract;


/**
 * Created by hxchen on 2018/4/21.
 */
public class CoolCoinClient{

    public static void main( String[] args ) throws Exception
    {
        Web3j web3j = Web3j.build(new HttpService("http://localhost:8545"));
        try {

            String account = web3j.ethAccounts().send().getAccounts().get(0);
            Credentials credentials = Credentials.create(account);
            //合约地址
            String address="0xd69A0599df3C0dd9ACAa0a9E47365730E9f4ee99";
            CoolCoin coolCoin = CoolCoin.load(address,web3j,credentials, Contract.GAS_PRICE,Contract.Contract.GAS_LIMIT);
            //待查询余额的账户地址
            String account2 = "0xc2298C3398584aaB380fafb564037D9Fb910e0a1";
            RemoteCall remoteCall= coolCoin.balanceOf(account);
            System.out.println("返回结果:"+remoteCall.send());
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

}

有关 web3j 更多可参考:web3j

全文涉及到的代码, 在这里