本周写实验，需要提供简单的后台接口对数据库进行增删改查，以前写后台只用过php和java,因为比较容易，用js写的也比较快，所以这次想用js实现简单的增删改查接口。
初始化
- 需要工具:nodejs
- 依赖:express,mysql,body-parser(这些都是npm的包)
为了能够解析js,需要下载nodejs,下载完nodejs,创建一个文件夹，使用npm init初始化,除了填写名字，一路确定下去，在文件夹下就会多出一个package.json文件.
// package.json{ "name": "test", "version": "1.0.0", "description": "", "main": "index.js", "scripts": { "test": "echo \"Error: no test specified\" && exit 1" }, "author": "", "license": "ISC"}为了接受并处理http请求,需要引入express这个包,在根目录下使用这个命令：
$ npm install express此时就引入了express这个包,创建一个index.js文件到根目录下,内容:
var express = require('express');var app = express();app.get('/', function(req, res) { res.send('hello world!');});app.listen(3000, function() { console.log('server now listening at 3000 port');});打开终端，使用nodejs编译index.js,并且打开浏览器输入localhost:3000就能看到hello world!了:
$ node index.jsserver now listening at 3000 port这说明我们已经监听了3000端口并且可以用js来处理http请求了.
连接数据库
我使用的是mysql数据库，为了方便操作数据库，引入mysql这个包:
$ npm install mysqlnpm WARN test@1.0.0 No descriptionnpm WARN test@1.0.0 No repository field.+ mysql@2.17.1added 9 packages from 14 contributors and audited 134 packages in 4.145sfound 0 vulnerabilities在index.js同路径下创建一个db.js专门用来处理数据库连接问题:
//db.jsvar mysql = require('mysql');var pool = mysql.createPool({ //连接信息 host: "localhost", user: "root", password: "", database: "c#learn", port: "3306"});var sql = { insert:'INSERT INTO teacher(name, username, email, sex) VALUES(?,?,?,?)', update:'update teacher set name=?, username=?, email=?, sex=? where id=?', delete: 'delete from teacher where id=?', queryById: 'select * from teacher where id=?', queryAll: 'select * from teacher'};function query(sql, data, callback) { pool.getConnection(function(err, connection) { connection.query(sql, data, function(err, rows) { callback(err, rows); connection.release(); //释放连接 }); });}exports.query = query;exports.sql = sql;配置数据库信息获得pool对象,就可以用pool对象来对数据库进行操作,在配置sql语句，将查询方法和sql语句导出给其他模块调用.
提供后台接口
在index.js导入db.js,并且将http请求和数据库操作对接:
var express = require('express');var app = express();var db = require('./db.js');app.get('/', function(req, res) { res.header("Access-Control-Allow-Origin", "*"); db.query(db.sql.queryAll, [], function(err, rows) { res.send(JSON.stringify(rows)); });});这时再访问localhost:3000就能看我们teacher表中所有的记录了。app.listen(3000, function() { console.log('server now listening at 3000 port');});
另外,为了读取post和put里的body信息,我们需要body-parser这个包:
$ npm install body-parser使用bodyParser来配置app:
//index.jsvar express = require('express');var db = require('./db.js');var app = express();var bodyParser = require('body-parser');app.use(bodyParser.json());这时就可以用req.body读取请求体了.
完整代码:
var express = require('express');var db = require('./db.js');var app = express();var bodyParser = require('body-parser');app.use(bodyParser.json());app.get('/', function(req, res) { res.header("Access-Control-Allow-Origin", "*"); db.query(db.sql.queryAll, [], function(err, rows) { console.log('err', err, 'rows', rows); res.send(JSON.stringify(rows)); });});app.get('/:id', function(req, res) { res.header("Access-Control-Allow-Origin", "*"); db.query(db.sql.queryById, [req.params.id], function(err, rows) { res.send(JSON.stringify(rows)); });});app.post('', function(req, res) { res.header("Access-Control-Allow-Origin", "*"); console.log(req.body.name); var teacher = req.body; db.query(db.sql.insert, [teacher.name, teacher.username, teacher.email, teacher.sex], function(err, rows) { if (err) { res.status(500); res.send('insert error'); } else { res.status(200); res.send('insert success'); } });});app.put('/:id', function(req, res) { res.header("Access-Control-Allow-Origin", "*"); var teacher = req.body; var array = [teacher.name, teacher.username, teacher.email, teacher.sex, req.params.id]; db.query(db.sql.update, array, function(err, rows) { if (err) { res.status(500); res.send('update error'); } else { res.status(200); res.send('update success'); } });});app.delete('/:id', function(req, res) { res.header("Access-Control-Allow-Origin", "*"); db.query(db.sql.delete, [req.params.id], function(err, rows) { if (err) { res.status(500); res.send('delete error'); } else { res.status(200); res.send('delete success'); } });});app.listen(3000, function() { console.log('server now listening at 3000 port');});总结
感觉算是理解了语言只是工具这句话.