Express 是一个小巧且灵活的 Node.js Web应用框架,它有一套健壮的特性,可用于开发单页、多页和混合Web应用。
npm安装
$ npm install express
创建http服务
//引入express
var express = require('express');
//执行express**函数
var app = express();
//监听端口
app.listen(3000);
根据请求路径来处理客户端发出的GET请求
app.get(path,function(req, res));
get方法使用:
const express = require('express');
const app = express();
app.get('/hello',function(req,res){
res.end('hello');
});
app.get('/world',function(req,res){
res.end('world');
});
app.get('*',function(req,res){
res.setHeader('Content-Type','text/plain;charset=utf8');
res.end('Not Found');
});
app.listen(3000);
get方法实现:
let url = require('url');
let express = function () {
let app = function (req, res) {
let {pathname} = url.parse(req.url, true);
let method = req.method.toLowerCase();
for (let i = 0; i < app.routes.length; i++) {
let {path, method, handler} = app.routes[i];
if ((path == pathname || path == "*") && method == req.method.toLowerCase()) {
return handler(req, res);
}
}
res.end(`CANNOT ${req.method} ${req.url}`);
}
app.routes = [];
app.listen = function (port) {
require('http').createServer(app).listen(port);
}
app.get = function (path, handler) {
app.routes.push({
path, handler, method: 'get'
});
}
return app;
}
module.exports = express;
根据请求路径来处理客户端发出的POST请求
app.post(path,function(req,res));
post方法的使用:
//引入express
var express = require('./express');
//执行express函数
var app = express();
//监听端口
app.post('/hello', function (req,res) {
res.end('hello');
});
app.post('*', function (req,res) {
res.end('post没找到');
});
app.listen(3000);
通过linux命令发送post请求
$ curl -X POST http://localhost:3000/hello
post的实现:
增加所有请求的方法
http.METHODS.forEach(function(method){
app[method] = function (path, handler) {
app.routes.push({
path, handler, method
});
}
});
监听所有的请求方法,可以匹配所有的HTTP动词。根据请求路径来处理客户端发出的所有请求
app.all(path,function(req, res));
all的方法使用:
const express = require('express');
const app = express();
app.all('/world',function(req,res){
res.end('all world');
});
app.listen(3000);
app.all = function (path, handler) {
app.routes.push({
path, handler, method: 'all'
});
}
中间件就是处理HTTP请求的函数,用来完成各种特定的任务,比如检查用户是否登录、检测用户是否有权限访问等,它的特点是:
中间件的使用方法:
增加中间件
var express = require('express');
var app = express();
app.use(function (req,res,next) {
console.log('全部匹配');
next();
});
app.use('/water', function (req,res,next) {
console.log('只匹配/water');
next();
});
app.get('/water', function (req,res) {
res.end('water');
});
app.listen(3000);
use方法的实现:在路由数组中增加中间件
app.use = function (path,fn) {
if(typeof fn !='function'){
fn = path;
path = '/';
}
app.routes.push({method:'middle',path:path,fn:fn});
}
let url = require('url');
let http = require('http');
let express = function () {
let app = function (req, res) {
let {pathname} = url.parse(req.url, true);
let method = req.method.toLowerCase();
let index = 0;
function next(err) {
if (index >= app.routes.length) {
return res.end(`CANNOT ${method} ${pathname}`);
}
let route = app.routes[index++];
if (route.method == 'middle') {
if (route.path == '/' || pathname.startsWith(route.path + '/') || route.path == pathname) {
route.handler(req, res, next);
} else {
next();
}
} else {
if ((route.path == pathname || route.path == "*") && (route.method == req.method.toLowerCase()) || method == 'all') {
return route.handler(req, res);
} else {
next();
}
}
}
next();
}
app.routes = [];
app.listen = function (port) {
http.createServer(app).listen(port);
}
http.METHODS.forEach(function (method) {
method = method.toLowerCase();
app[method] = function (path, handler) {
app.routes.push({
path, handler, method
});
}
});
app.all = function (path, handler) {
app.routes.push({
path, handler, method: 'all'
});
}
app.use = function (path, handler) {
if (typeof handler != 'function') {
handler = path;
path = "/";
}
app.routes.push({
method: 'middle',
path,
handler
});
}
return app;
}
module.exports = express;
错误中间件:next中可以传递错误,默认执行错误中间件
var express = require('express');
var app = express();
app.use(function (req,res,next) {
console.log('过滤石头');
next('stone is too big');
});
app.use('/water', function (req,res,next) {
console.log('过滤沙子');
next();
});
app.get('/water', function (req,res) {
res.end('water');
});
app.use(function (err,req,res,next) {
console.log(err);
res.end(err);
});
app.listen(3000);
错误中间件的实现:对错误中间件进行处理
let url = require('url');
let http = require('http');
let express = function () {
let app = function (req, res) {
let {pathname} = url.parse(req.url, true);
let method = req.method.toLowerCase();
let index = 0;
function next(err) {
if (index >= app.routes.length) {
return res.end(`CANNOT ${method} ${pathname}`);
}
let route = app.routes[index++];
if (err) {
if (route.method == 'middle' && route.handler.length == 4) {
route.handler(req, res, next)
}
}
if (route.method == 'middle') {
if (route.path == '/' || pathname.startsWith(route.path + '/') || route.path == pathname) {
route.handler(req, res, next);
} else {
next();
}
} else {
if ((route.path == pathname || route.path == "*") && (route.method == req.method.toLowerCase()) || method == 'all') {
return route.handler(req, res);
} else {
next();
}
}
}
next();
}
app.routes = [];
app.listen = function (port) {
http.createServer(app).listen(port);
}
http.METHODS.forEach(function (method) {
method = method.toLowerCase();
app[method] = function (path, handler) {
app.routes.push({
path, handler, method
});
}
});
app.all = function (path, handler) {
app.routes.push({
path, handler, method: 'all'
});
}
app.use = function (path, handler) {
if (typeof handler != 'function') {
handler = path;
path = "/";
}
app.routes.push({
method: 'middle',
path,
handler
});
}
return app;
}
module.exports = express;
req.hostname
返回请求头里取的主机名req.path
返回请求的URL的路径名req.query
查询字符串//http://localhost:3000/?name=zfpx&age=8
app.get('/',function(req,res){
res.write(JSON.stringify(req.query))
res.end(req.path+" "+req.path);
});
具体实现:对请求增加方法
req.path = pathname;
req.query = query;
req.params 匹配到的所有路径参数组成的对象
app.get('/school/:name/:age', function (req,res) {
console.log(req.params);
res.end('water');
});
params实现:增加params属性
let url = require('url');
let http = require('http');
let express = function () {
let app = function (req, res) {
let {pathname, query} = url.parse(req.url, true);
let method = req.method.toLowerCase();
let index = 0;
req.path = pathname;
req.query = query;
function next(err) {
if (index >= app.routes.length) {
return res.end(`CANNOT ${method} ${pathname}`);
}
let route = app.routes[index++];
if (err) {
if (route.method == 'middle' && route.handler.length == 4) {
route.handler(req, res, next)
} else {
next();
}
} else {
if (route.method == 'middle') {
if (route.path == '/' || pathname.startsWith(route.path + '/') || route.path == pathname) {
route.handler(req, res, next);
} else {
next();
}
} else {
if (route.paramNames) {
let matchers = pathname.match(new RegExp(route.path));
if (matchers) {
let params = {};
for(let i=0;i<route.paramNames.length;i++){
params[route.paramNames[i]] = matchers[i+1];
}
req.params = params;
route.handler(req,res);
}else{
next();
}
} else {
if ((route.path == pathname || route.path == "*") && (route.method == req.method.toLowerCase()) || method == 'all') {
return route.handler(req, res);
} else {
next();
}
}
}
}
}
next();
}
app.routes = [];
app.listen = function (port) {
http.createServer(app).listen(port);
}
http.METHODS.forEach(function (method) {
method = method.toLowerCase();
app[method] = function (path, handler) {
const layer = {path, handler, method};
if (path.includes(':')) {
let paramNames = [];
layer.path = path.replace(/:([^\/]+)/g, function () {
paramNames.push(arguments[1]);
return '([^\/]+)';
});
layer.paramNames = paramNames;
}
app.routes.push(layer);
}
});
app.all = function (path, handler) {
app.routes.push({
path, handler, method: 'all'
});
}
app.use = function (path, handler) {
if (typeof handler != 'function') {
handler = path;
path = "/";
}
app.routes.push({
method: 'middle',
path,
handler
});
}
return app;
}
module.exports = express;
参数为要响应的内容,可以智能处理不同类型的数据,在输出响应时会自动进行一些设置,比如HEAD信息、HTTP缓存支持等等
res.send([body]);
当参数是一个字符串时,这个方法会设置Content-type为text/html
app.get('/', function (req,res) {
res.send('<p>hello world</p>');
});
当参数是一个Array或者Object,这个方法返回json格式
app.get('/json', function (req,res) {
res.send({obj:1});
});
app.get('/arr', function (req,res) {
res.send([1,2,3]);
});
当参数是一个number类型,这个方法返回对应的状态码短语
app.get('/status', function (req,res) {
res.send(404); //not found
//res.status(404).send('没有找到');设置短语
});
send方法的实现:自定义send方法
res.send = function(msg){
let type = typeof msg;
if(type == 'object'){
res.setHeader('Content-Type','application/json');
msg = JSON.stringify(msg);
}else if(type == 'number'){
res.setHeader('Content-Type','application/plain');
res.status(msg);
res.end(http.STATUS_CODES[msg]);
}else{
res.setHeader('Content-Type','application/html');
res.end(msg);
}
}
npm安装ejs
$ npm install ejs
使用ejs模版
var express = require('express');
var path = require('path');
var app = express();
app.set('view engine','ejs');
app.set('views',path.join(__dirname,'views'));
app.listen(3000);
配置成html格式
app.set('view engine','html')
app.set('views',path.join(__dirname,'views'));
app.engine('html',require('ejs').__express);
app.get('/', function (req,res) {
res.render('hello',{title:'hello'},function(err,data){});
});
读取模版渲染
res.render = function (name, data) {
var viewEngine = engine.viewEngineList[engine.viewType];
if (viewEngine) {
viewEngine(path.join(engine.viewsPath, name + '.' + engine.viewType), data, function (err, data) {
if (err) {
res.status(500).sendHeader().send('view engine failure' + err);
} else {
res.status(200).contentType('text/html').sendHeader().send(data);
}
});
} else {
res.status(500).sendHeader().send('view engine failure');
}
}
如果要在网页中加载静态文件(css、js、img),就需要另外指定一个存放静态文件的目录,当浏览器发出非HTML文件请求时,服务器端就会到这个目录下去寻找相关文件
var express = require('express');
var app = express();
var path = require('path');
app.use(express.static(path.join(__dirname,'public')));
app.listen(3000);
配置静态服务器
express.static = function (p) {
return function (req, res, next) {
var staticPath = path.join(p, req.path);
var exists = fs.existsSync(staticPath);
if (exists) {
res.sendFile(staticPath);
} else {
next();
}
}
};
redirect方法允许网址的重定向,跳转到指定的url并且可以指定status,默认为302方式。
res.redirect([status], url);
使用重定向
app.get('/', function (req,res) {
res.redirect('http://www.baidu.com')
});
302重定向
res.redirect = function (url) {
res.status(302);
res.headers('Location', url || '/');
res.sendHeader();
res.end();
};
安装body-parser
$ npm install body-parser
接收请求体中的数据
app.get('/login', function (req,res) {
res.sendFile('./login.html',{root:__dirname})
});
app.post('/user', function (req,res) {
console.log(req.body);
res.send(req.body);
});
app.listen(3000);
实现bodyParser
function bodyParser () {
return function (req,res,next) {
var result = '';
req.on('data', function (data) {
result+=data;
});
req.on('end', function () {
try{
req.body = JSON.parse(result);
}catch(e){
req.body = require('querystring').parse(result);
}
next();
})
}
};