使用Koa2搭建web项目

Posted 2020-11-18 bijian1013

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　　随着Node.js的日益火热，各种框架开始层出不穷的涌现出来，Node.js也开始逐渐的被应用到处理服务端请求的场景中。搭建Web项目的框架也随之开始出现——express、koa、koa2、egg等，当然要了解其好坏还是要自己去啃源码的。本文将不会涉及到源码，只是带领初学者简单了解下Koa2的基本使用，欢迎大家在评论中互相交流学习。
注意：koa2使用了ES7的语法，所以使用时请升级Node版本到最新。　

　　了解更详细的源码信息可以到git上的koajs/koa去了解。

1.项目目录结构

2. 代码逻辑解析

2.1. 包结构文件

{
  "name": "weixin-node-koa",
  "version": "1.0.0",
  "description": "node.js with koa2",
  "private": true,
  "dependencies": {
    "koa": "^2.0.0",
    "koa-router": "^7.0.0",
    "mysql":"2.13.0"
  },
  "scripts": {
    "start": "node app.js"
  },
  "engines": {
    "node": ">=6.0.0"
  },
  "author": "Fly",
  "license": "CENTERM"
}

2.2. 启动入口文件

app.js

const Koa = require(\'koa\');
const app = new Koa();
const router2controller = require(\'./app/router2controller.js\');
const config = require(\'./config/config.local.js\');

app.use(router2controller());
app.listen(config.port);
console.log("Server started and listen on port " + config.port);

如果请求的报文体是XML格式，可以添加下面的代码自动解析报文（注意引用koa-xxx的版本要与koa2对应）

const Koa = require(\'koa\');
const app = new Koa();
const router2controller = require(\'./app/router2controller.js\');
const config = require(\'./config/config.local.js\');

//start接收到的xml数据请求单独解析存储
const xmlParser = require(\'koa-xml-body\');
app.use(xmlParser()).use((ctx,next) => {
    ctx.data = ctx.request.body;
    return next();
});
//end

app.use(router2controller());
app.listen(config.port);
console.log("Server started and listen on port " + config.port);

从代码看到引入了一个router2controller.js的文件，这个文件是完成前端请求到具体处理方法的路由过程

2.3. 路由器文件

router2controller.js，该类将会自动扫描controller文件夹中的文件来加载请求映射，不需要挨个请求单独配置

koa-router原生提供方法如下：

router
.get(\'/\', async (ctx,next) => {
this.body = \'Hello World!\';
})
.post(\'/users\', async (ctx,next) => {
//TODO
})
.put(\'/users/:id\', async (ctx,next) => {
//TODO
})
.del(\'/users/:id\', async (ctx,next) => {
//TODO
});

自动扫描controller包实现方法如下

const fs = require(\'fs\');
const router = require(\'koa-router\')();

function addMapping(router, mapping) {
    for (var url in mapping) {
        if (url.startsWith(\'GET \')) {
            var path = url.substring(4);
            router.get(path, mapping[url]);
            console.log(`register URL mapping: GET ${path}`);
        } else if (url.startsWith(\'POST \')) {
            var path = url.substring(5);
            router.post(path, mapping[url]);
            console.log(`register URL mapping: POST ${path}`);
        } else if (url.startsWith(\'PUT \')) {
            var path = url.substring(4);
            router.put(path, mapping[url]);
            console.log(`register URL mapping: PUT ${path}`);
        } else if (url.startsWith(\'DELETE \')) {
            var path = url.substring(7);
            router.del(path, mapping[url]);
            console.log(`register URL mapping: DELETE ${path}`);
        } else {
            console.log(`invalid URL: ${url}`);
        }
    }
}

function addControllers(router, dir) {
    fs.readdirSync(__dirname + \'/\' + dir).filter((f) => {
        return f.endsWith(\'.js\');
    }).forEach((f) => {
        console.log(`process controller: ${f}...`);
        let mapping = require(__dirname + \'/\' + dir + \'/\' + f);
        addMapping(router, mapping);
    });
}

module.exports = function (dir) {
    var controllersDir = dir || \'controller\';
    addControllers(router, controllersDir);
    return router.routes();
};

2.4. 控制器

userController.js，***Controller.js是用来处理具体请求信息以及返回数据的，userController.js中处理了GET请求获取用户信息，POST请求保存用户信息

const userService = require(\'./../service/userService.js\');

var getUserinfo = (ctx, next) => {
    let query = ctx.query;
    let userId = query.id;
    let userInfo = userService.getUserById(userId);

    let html = \'<html><body>\'
        + \'<div> userinfo:&nbsp;\' + userInfo + \'</div>\'
        + \'</body></html>\';
    ctx.response.type =\'text/html\';
    ctx.response.body = html;
};

var saveUserinfo = (ctx, next) => {
    const requestString = ctx.data;
    //TODO数据处理
    Console.log(requestString);
};

module.exports = {
    \'GET /getUserinfo\': getUserinfo,
    \'POST /saveUserinfo\': saveUserinfo
};

2.5. 数据处理

userService.js，处理封装从***Dao.js获取到的数据返回给Controller

const userDao = require(\'./../dao/userDao.js\');

var getUserById = async (userId) => {
    var users = userDao.getUserById(userId);
    var responseContent = \'\';
    for(let user of users) {
        reaponseContent += \'姓名：\' + user.name + \'&nbsp;|\';
        reaponseContent += \'年龄：\' + user.age + \'&nbsp;|\';
        reaponseContent += \'身高：\' + user.height + \'<br />\';
    }
    return responseContent;
}

module.exports = {
    getUserById : getUserById
};

2.6. 数据获取

userDao.js，通过请求传入参数来获取user数据

const mysql = require(\'./../utils/mysqlUtil.js\');

var getUserById = async (userId) => {
    let mysqlOptions = {
        sql : \'select * from table_user where user_id = ?\',
        args : [userId]
    };

    var users = await mysql.execQuery(mysqlOptions);
    if(users.length == 0) {
        return null;
    } else {
        return users;
    }
};

module.exports = {
    getUserById : getUserById
};

2.7. 数据库操作

mysqlUtil.js，包含了数据库连接池控制，连接建立、释放管理，执行Dao发起的数据库操作请求

const mysql = require(\'mysql\');
const config = require(\'./../../config/config.local.js\');

var connectionPool = mysql.createPool({
    \'host\' : config.database.host,
    \'port\':config.database.port,
    \'user\' : config.database.user,
    \'password\' : config.database.password,
    \'database\' : config.database.database,
    \'charset\': config.database.charset,
    \'connectionLimit\': config.database.connectionLimit,
    \'supportBigNumbers\': true,
    \'bigNumberStrings\': true
});

var release = connection => {
    connection.end(function(error) {
        if(error) {
            console.log(\'Connection closed failed.\');
        } else {
            console.log(\'Connection closed succeeded.\');
        }
    });
};

var execQuery = sqlOptions => {
    var results = new Promise((resolve, reject) => {
            connectionPool.getConnection((error,connection) => {
            if(error) {
                console.log("Get connection from mysql pool failed !");
                throw error;
            }

            var sql = sqlOptions[\'sql\'];
            var args = sqlOptions[\'args\'];

            if(!args) {
                var query = connection.query(sql, (error, results) => {
                    if(error) {
                        console.log(\'Execute query error !\');
                        throw error;
                    }

                    resolve(results);
                });
            } else {
                var query = connection.query(sql, args, function(error, results) {
                    if(error) {
                        console.log(\'Execute query error !\');
                        throw error;
                    }

                    resolve(results);
                });
            }

            connection.release(function(error) {
                if(error) {
                    console.log(\'Mysql connection close failed !\');
                    throw error;
                }
            });
        });
    }).then(function (chunk) {
        return chunk;
    });

    return results;
};

module.exports = {
    release : release,
    execQuery : execQuery
}

此实例我并没有整理并在本机运行过，但这个包结构的思路还是值得学习的，整个实例的代码详见http://bijian1013.iteye.com/blog/2425085。

文章来源：https://blog.csdn.net/ererfei/article/details/68060551

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