关键词:
利用Node.js开发与合约交互的Web界面
零、在私有链上部署合约
// 本文中用到的MetaCoin合约
pragma solidity ^0.4.2;
contract MetaCoin
mapping (address => uint) balances;
event Transfer(address indexed _from, address indexed _to, uint256 _value);
function MetaCoin()
balances[tx.origin] = 10000;
function sendCoin(address receiver, uint amount) returns(bool sufficient)
if (balances[msg.sender] < amount) return false;
balances[msg.sender] -= amount;
balances[receiver] += amount;
Transfer(msg.sender, receiver, amount);
return true;
function getBalance(address addr) returns(uint)
return balances[addr];
一、新建一个项目
新建一个node.js项目并初始化
$ mkdir web3test && cd web3test
$ npm init
二、导入web3.js
npm install web3 --save
三、创建web3对象
var Web3 = require("web3");
//创建web3对象
var web3 = new Web3();
// 连接到以太坊节点
web3.setProvider(new Web3.providers.HttpProvider("http://localhost:8545"));
可以测试一下:
var version = web3.version.node;
console.log(version);
==>
在app目录下,终端输入:
prodeMacBook-Pro:web3test pro$ node app.js
输出:
Geth/linoy/v1.6.5-stable-cf87713d/darwin-amd64/go1.8.3
四、调用合约
部署合约:
私有链上查看地址,abi可以通过here获取
var abi = ["constant":false,"inputs":["name":"receiver","type":"address","name":"amount","type":"uint256"],"name":"sendCoin","outputs":["name":"sufficient","type":"bool"],"payable":false,"stateMutability":"nonpayable","type":"function","constant":false,"inputs":["name":"addr","type":"address"],"name":"getBalance","outputs":["name":"","type":"uint256"],"payable":false,"stateMutability":"nonpayable","type":"function","inputs":[],"payable":false,"stateMutability":"nonpayable","type":"constructor","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"];
var address = "0x6a0a87bd4da65b39a1b27597edb1a5b505a55a0b";
var metacoin = web3.eth.contract(abi).at(address);
调用合约:
/* 查看账户余额 */
var account_one = web3.eth.accounts[0];
var account_one_balance = metacoin.getBalance.call(account_one);
console.log("account one balance: ", account_one_balance.toNumber());
===>
终端查看:
prodeMacBook-Pro:web3test pro$ node app.js
account one balance: 10000
/* 转账操作 */
var account_one = web3.eth.accounts[0];
var account_two = web3.eth.accounts[1];
var txhash = metacoin.sendCoin.sendTransaction(account_two, 100, from: account_one );
var myEvent = metacoin.Transfer();
myEvent.watch(function (err, result)
if (!err)
if (result.transactionHash == txhash)
var account_one_balance = metacoin.getBalance.call(account_one);
console.log("account one balance after sendCoin:", account_one_balance.toNumber());
else
console.log(err);
myEvent.stopWatching();
);
====>
这里可能会遇到错误:Error: authentication needed: password or unlock
原因是账户没有解锁:在终端,personal.unlockAccount(user1, "123456")
然后再次尝试可以看到:
account one balance: 10000
account one balance after sendCoin: 9900
创建账户:
var account_three = web3.personal.newAccount("123456");
console.log(account_three);
五、与web界面交互
1 . 安装express
查看:here
npm install express --save
2 . 导入BigNumber.js
处理大数字需要使用BigNumber库
npm install --save bignumber.js
===>
var BigNumber = require('bignumber.js');
3 . 调用合约
a. call
var returnValue = metacoin.getBalance.call(address).toString();
b. sendTransaction
var txhash = metacoin.sendCoin.sendTransaction(address_b, trans_value, from:address_a);
4 . 界面
六、代码部分
1 . app.js代码
/* 现连接到geth节点,并获取已部署合约的引用 */
var express = require("express");
var app = express();
var server = require("http").createServer(app);
var io = require("socket.io")(server);
var BigNumber = require('bignumber.js');
app.use(express.static("public"));
app.get("/", function(req, res)
res.sendFile(__dirname + "/index.html");
)
// 现连接到geth节点
var Web3 = require("web3");
web3 = new Web3(new Web3.providers.HttpProvider("http://localhost:8545"));
/* 部署合约 */
var abi = ["constant":false,"inputs":["name":"receiver","type":"address","name":"amount","type":"uint256"],"name":"sendCoin","outputs":["name":"sufficient","type":"bool"],"payable":false,"stateMutability":"nonpayable","type":"function","constant":false,"inputs":["name":"addr","type":"address"],"name":"getBalance","outputs":["name":"","type":"uint256"],"payable":false,"stateMutability":"nonpayable","type":"function","inputs":[],"payable":false,"stateMutability":"nonpayable","type":"constructor","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"];
var address = "0x6a0a87bd4da65b39a1b27597edb1a5b505a55a0b";
var metacoin = web3.eth.contract(abi).at(address);
app.get("/register", function(req, res)
//获取输入的密码
var password = req.query.password;
//创建账户
var account = web3.personal.newAccount(password);
res.send(account);
)
app.get("/getBalance", function(req, res)
var address = req.query.address;
//获取address的余额
var returnValue = metacoin.getBalance.call(address).toString();
res.send(returnValue);
)
app.get("/sendcoin", function(req, res)
var address_a = req.query.address_a;
var address_b = req.query.address_b;
var trans_value = req.query.trans_value;
//转账操作
var txhash = metacoin.sendCoin.sendTransaction(address_b, trans_value, from:address_a);
res.send(txhash);
)
server.listen(8080);
2 . html代码
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<title>转账操作</title>
<link rel="stylesheet" href="">
</head>
<body>
<div>
<div>
<h3>注册:</h3><br>
<label for="identity">请输入密码:</label><input type="text" id="password" ></input>
<button type = "submit" onclick="register()">注册</button>
<p id = "address_test">地址:</p>
</div>
<div>
<h3>查询余额:</h3><br>
<label for="identity">请输入地址:</label><input type="text" id="address" ></input>
<button type = "submit" onclick="getBalance()">查询余额</button>
<p id = "address_balance">余额:</p>
</div>
<div>
<h3>转账</h3>
<label for="identity">转出用户地址</label><input type="text" id="address_a" ></input>
<br><label for="identity">转入用户地址</label><input type="text" id="address_b" ></input>
<br><label for="identity">金额</label><input type="text" id="trans_value" ></input>
<button type = "submit" onclick="sendcoin()">确定</button>
<p id = "tx_hash">交易:</p>
</div>
</div>
<script type="text/javascript" src="/sha1.min.js"></script>
<script type="text/javascript" src="/jquery.min.js"></script>
<script type="text/javascript" src="/socket.io.min.js"></script>
<script type="text/javascript" src="/main.js"></script>
<script type="text/javascript" src="/bignumber.js"></script>
</body>
</html>
3 . main.js代码
function register()
var password = document.getElementById("password").value;
$.get("/register?password=" + password, function(data)
if(data == "Error")
$("#address_test").text("An error occured.");
else
$("#address_test").html("地址: " + data);
);
function getBalance()
var address = document.getElementById("address").value;
$.get("/getBalance?address=" + address, function(data)
if(data == "Error")
$("#address_balance").text("An error occured.");
else
$("#address_balance").html("余额: " + data);
);
function sendcoin()
var address_a = document.getElementById("address_a").value;
var address_b = document.getElementById("address_b").value;
var trans_value = document.getElementById("trans_value").value;
var tx_hash = document.getElementById("tx_hash").value;
//转账
$.get("/sendcoin?address_a=" + address_a + "&address_b=" + address_b + "&trans_value=" + trans_value, function(data)
$("#tx_hash").html("交易: " + data);
);
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