摘要：本周寫實驗，需要提供簡單的后臺接口對數(shù)據(jù)庫進行增刪改查，以前寫后臺只用過和因為比較容易，用寫的也比較快，所以這次想用實現(xiàn)簡單的增刪改查接口。

本周寫實驗，需要提供簡單的后臺接口對數(shù)據(jù)庫進行增刪改查，以前寫后臺只用過php和java,因為比較容易，用js寫的也比較快，所以這次想用js實現(xiàn)簡單的增刪改查接口。

需要工具:nodejs

依賴:express,mysql,body-parser(這些都是npm的包)

為了能夠解析js,需要下載nodejs,下載完nodejs,創(chuàng)建一個文件夾，使用npm init初始化,除了填寫名字，一路確定下去，在文件夾下就會多出一個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"
}

為了接受并處理http請求,需要引入express這個包,在根目錄下使用這個命令：

$ npm install express

此時就引入了express這個包,創(chuàng)建一個index.js文件到根目錄下,內(nèi)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");
});

打開終端，使用nodejs編譯index.js,并且打開瀏覽器輸入localhost:3000就能看到hello world!了:

$ node index.js
server now listening at 3000 port

這說明我們已經(jīng)監(jiān)聽了3000端口并且可以用js來處理http請求了.

我使用的是mysql數(shù)據(jù)庫，為了方便操作數(shù)據(jù)庫，引入mysql這個包:

$ npm install mysql
npm WARN [email protected] No description
npm WARN [email protected] No repository field.

+ [email protected]
added 9 packages from 14 contributors and audited 134 packages in 4.145s
found 0 vulnerabilities

在index.js同路徑下創(chuàng)建一個db.js專門用來處理數(shù)據(jù)庫連接問題:

//db.js
var mysql = require("mysql");
var pool = mysql.createPool({ //連接信息
  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(); //釋放連接
    });
  });
}
exports.query = query;
exports.sql = sql;

配置數(shù)據(jù)庫信息獲得pool對象,就可以用pool對象來對數(shù)據(jù)庫進行操作,在配置sql語句，將查詢方法和sql語句導(dǎo)出給其他模塊調(diào)用.

在index.js導(dǎo)入db.js,并且將http請求和數(shù)據(jù)庫操作對接:

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));
    });
});
這時再訪問localhost:3000就能看我們teacher表中所有的記錄了。
app.listen(3000, function() {
    console.log("server now listening at 3000 port");
});

另外,為了讀取post和put里的body信息,我們需要body-parser這個包:

$ npm install body-parser

使用bodyParser來配置app:

//index.js
var express = require("express");
var db = require("./db.js");
var app = express();
var bodyParser = require("body-parser");

app.use(bodyParser.json());

這時就可以用req.body讀取請求體了.
完整代碼:

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");
});

感覺算是理解了語言只是工具這句話.