使用Eggjs(koa) & web3.js开发你的以太坊Dapp
Eggjs
Eggjs 是阿里开源的企业级基于Koa2的Node.js框架. eggjs基本上是开箱即用,奉行『约定优于配置』.在日常开发中,用起来非常顺畅. 而且生态也比较完善,koa2的插件都可以对接到框架中来.
Egg.js 目录结构
egg-project
├── package.json
├── app.js (可选)
├── agent.js (可选)
├── app
| ├── router.js
│ ├── controller
│ | └── home.js
│ ├── service (可选)
│ | └── user.js
│ ├── middleware (可选)
│ | └── response_time.js
│ ├── schedule (可选)
│ | └── my_task.js
│ ├── public (可选)
│ | └── reset.css
│ ├── view (可选)
│ | └── home.tpl
│ └── extend (可选)
│ ├── helper.js (可选)
│ ├── request.js (可选)
│ ├── response.js (可选)
│ ├── context.js (可选)
│ ├── application.js (可选)
│ └── agent.js (可选)
├── config
| ├── plugin.js
| ├── config.default.js
│ ├── config.prod.js
| ├── config.test.js (可选)
| ├── config.local.js (可选)
| └── config.unittest.js (可选)
└── test
├── middleware
| └── response_time.test.js
└── controller
└── home.test.js
如上，由框架约定的目录：
app/router.js用于配置 URL 路由规则。app/controller/**用于解析用户的输入，处理后返回相应的结果。app/service/**用于编写业务逻辑层，可选，建议使用。app/middleware/**用于编写中间件，可选。app/public/**用于放置静态资源，可选，具体参见内置插件 egg-static。app/extend/**用于框架的扩展，可选。config/config.{env}.js用于编写配置文件。config/plugin.js用于配置需要加载的插件。test/**用于单元测试。app.js和agent.js用于自定义启动时的初始化工作，可选。
由内置插件约定的目录：
app/public/**用于放置静态资源，可选，具体参见内置插件 egg-static。app/schedule/**用于定时任务，可选。
若需自定义自己的目录规范，参见 Loader API - app/view/** 用于放置模板文件，可选，由模板插件约定。 - app/model/** 用于放置领域模型，可选，由领域类相关插件约定，如 egg-sequelize。
web3.js
为了让你的DAPP能够访问区块链上的数据，一种选择是使用web3.js提供的web3对象。底层实现上，它通过RPC 调用与本地节点通信。web3.js可以与任何暴露了RPC接口的区块链节点连接。
引入方式
在egg.js 自定义启动方式
//app.js
'use strict';
const Web3 = require('web3');
module.exports = app => {
app.beforeStart(async () => {
const { config } = app;
let originWeb3;
// web3 初始化
if (typeof originWeb3 !== 'undefined') {
console.warn("Using web3 detected from external source. If you find that your accounts don't appear or you have 0 MetaCoin, ensure you've configured that source properly. If using MetaMask, see the following link. Feel free to delete this warning. :) http://truffleframework.com/tutorials/truffle-and-metamask");
// Use Mist/MetaMask's provider
originWeb3 = new Web3(originWeb3.currentProvider);
} else {
console.warn(`No web3 detected. Falling back to http://${config.web3.host}:${config.web3.port}. You should remove this fallback when you deploy live, as it\'s inherently insecure. Consider switching to Metamask for development. More info here: http://truffleframework.com/tutorials/truffle-and-metamask`);
// fallback - use your fallback strategy (local node / hosted node + in-dapp id mgmt / fail)
originWeb3 = new Web3(new Web3.providers.HttpProvider(`http://${config.web3.host}:${config.web3.port}`));
}
// 把web3js挂载到app下
app.web3 = originWeb3;
// 创建一个上下文,用来调用service的方法
const ctx = app.createAnonymousContext();
app.cities = await ctx.service.connection.getAdmin();
});
};
Service层调用智能合约
// app/service/
'use strict';
const Service = require('egg').Service;
const contract = require('truffle-contract');
// 引入只能合约
const stock_artifact = require('../../build/contracts/Stock.json');
//链接合约
const Stock = contract(stock_artifact);
let adminAddress;
let meta;
class ConnectionService extends Service {
constructor(...args) {
super(...args);
this.web3 = this.app.web3;
}
setProvider() {
Stock.setProvider(this.web3.currentProvider);
// 解决apply报错
if (typeof Stock.currentProvider.sendAsync !== 'function') {
Stock.currentProvider.sendAsync = function() {
return Stock.currentProvider.send.apply(
Stock.currentProvider, arguments
);
};
}
}
getAccounts() {
return new Promise((resolve, reject) => {
this.setProvider();
// Get the initial account balance so it can be displayed.
// 使用web3.js 与只能合约交互
this.web3.eth.getAccounts(function(err, accs) {
if (err != null) {
console.log('There was an error fetching your accounts.');
reject('There was an error fetching your accounts.');
return;
}
if (accs.length === 0) {
console.log("Couldn't get any accounts! Make sure your Ethereum client is configured correctly.");
reject("Couldn't get any accounts! Make sure your Ethereum client is configured correctly.");
return;
}
this.accounts = accs;
resolve(this.accounts);
});
});
}
getBalance(account) {
return new Promise((resolve, reject) => {
this.setProvider();
Stock.deployed().then(function(instance) {
meta = instance;
return meta.getBalance.call(account, { from: adminAddress });
}).then(function(value) {
resolve({
shareLotsLength: value[0],
total: value[1],
});
})
.catch(function(e) {
console.log(e);
reject('Error 404');
});
});
}
// 添加用户
async addMember(address, name, empNo) {
if (!this.adminAddress) {
await this.getAdmin();
}
this.setProvider();
return new Promise((resolve, reject) => {
Stock.deployed().then(instance => {
meta = instance;
return meta.addMember(address, name, Number(empNo), { from: adminAddress || '0x0000000000000000000000000000000000000000' });
}).then(value => {
let args = 'not found';
for (let i = 0; i < value.logs.length; i++) {
const log = value.logs[i];
if (log.event === 'addmember') {
args = log.args;
break;
}
}
resolve(args);
})
.catch(e => {
console.log(e);
reject('add Member error');
})
;
});
}
// 获取用户
getAdmin() {
return new Promise((resolve, reject) => {
this.setProvider();
Stock.deployed().then(instance => {
return instance.getAdmin.call();
}).then(value => {
adminAddress = value;
resolve(value);
})
.catch(e => {
console.log(e);
reject('getAdmin error');
});
});
}
}
module.exports = ConnectionService;
完整Demo: https://github.com/Fantasy9527/egg-block-chain
Demo 使用方法
全局安装truffle
npm install -g truffle
智能合约
# 转移
truffle migrate
#编译合约
truffle compile
本地开发
$ npm i
$ npm run dev
$ open http://localhost:7001/
部署
$ npm start
$ npm stop
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