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1. Express 介绍 #

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。

express

2. Express 的应用 #

2.1 安装express #

npm安装

$ npm install express
2.2 使用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);
2.3 express的get方法 #

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;
2.4 express的post方法 #

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
            });
        }
});
2.5 express的all方法 #

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'
        });
    }
2.6 中间件 #

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;
2.7 获取参数和查询字符串 #
//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;
2.8 获取params参数 #

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;
2.9 express中的send方法 #

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);
            }
        }

3. 模板的应用 #

3.1 安装ejs #

npm安装ejs

$ npm install ejs
3.2 设置模板 #

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);
3.3 渲染html #

配置成html格式

app.set('view engine','html')
app.set('views',path.join(__dirname,'views'));
app.engine('html',require('ejs').__express);
3.4 渲染视图 #
app.get('/', function (req,res) {
    res.render('hello',{title:'hello'},function(err,data){});
});
3.5 模板的实现 #

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');
    }
}

4. 静态文件服务器 #

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);
4.1 静态文件服务器实现 #

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();
        }
    }
};

5. 重定向 #

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);
5.1 redirect使用 #

使用重定向

app.get('/', function (req,res) {
    res.redirect('http://www.baidu.com')
});
5.2 redirect的实现 #

302重定向

res.redirect = function (url) {
    res.status(302);
    res.headers('Location', url || '/');
    res.sendHeader();
    res.end();
};

6. 接收 post 响应体 #

安装body-parser

$ npm install body-parser
6.1 使用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);
6.2 req.body的实现 #

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();
        })
    }
};

源代码地址 #

https://github.com/YataoZhang/mockxpress