一、什么是服务端渲染

客户端请求服务器，服务器根据请求地址获得匹配的组件，在调用匹配到的组件返回Promise (官方是asyncData方法)来将需要的数据拿到。最后再通过window.__initial_state=data将其写入网页，最后将服务端渲染好的网页返回回去。接下来客户端将用新的store状态把原来的store状态替换掉，保证客户端和服务端的数据同步。遇到没被服务端渲染的组件，再去发异步请求拿数据。

服务端渲染的环境搭建

这是vue官网的服务端渲染的示意图，ssr有两个入口文件，分别是客户端的入后文件和服务端的入口文件，webpack通过两个入口文件分别打包成给服务端用的server bundle和给客户端用的client bundle.当服务器接收到了来自客户端的请求之后，会创建一个渲染器bundleRenderer，这个bundleRenderer会读取上面生成的server bundle文件，并且执行它的代码， 然后发送一个生成好的html到浏览器，等到客户端加载了client bundle之后，会和服务端生成的DOM进行Hydration(判断这个DOM和自己即将生成的DOM是否相同，如果相同就将客户端的vue实例挂载到这个DOM上)

实现步骤：

1、创建vue实例（main.js）

importVuefrom'vue'importAppfrom'./App.vue'importiViewfrom'iview';import{createStore}from'./store'import{createRouter}from'./router'import{sync}from'vuex-router-sync'Vue.use(iView);export functioncreateApp() {conststore = createStore()constrouter = createRouter()sync(store,router)constapp =newVue({router,store,render: h => h(App)})return{app,router,store}}

因为要做服务端渲染，所以这里不需要再用el去挂载，现将app、router、store导出

2、服务端入口文件（entry-server.js）

import{ createApp }from'./main'constisDev = process.env.NODE_ENV !=='production'const{ app,router,store } = createApp()constgetAllAsyncData=function(component){letstores = []functionloopComponent(component) {if(typeofcomponent.asyncData !=='undefined') {for(letaofcomponent.asyncData({store,route: router.currentRoute})) {stores.push(a)}}if(typeofcomponent.components !=='undefined') {for(letcincomponent.components){loopComponent(component.components[c])}}}loopComponent(component)returnstores}export defaultcontext => {return newPromise((resolve,reject) => {consts = isDev && Date.now()const{url} = contextconstfullPath = router.resolve(url).route.fullPathif(fullPath !== url) {reject({url: fullPath })}router.push(url)router.onReady(() => {constmatchedComponents = router.getMatchedComponents()if(!matchedComponents.length) {reject({code:404})}letallAsyncData = getAllAsyncData(matchedComponents[0])Promise.all(allAsyncData).then(() => {isDev && console.log(`data pre-fetch:${Date.now() - s}ms`)context.state = store.stateresolve(app)}).catch(reject)},reject)})}

这个文件的主要工作是接受从服务端传递过来的context参数，context包含当前页面的url，用getMatchedComponents方法获取当前url下的组件，返回一个数组，遍历这个数组中的组件，如果组件有asyncData钩子函数，则传递store获取数据，最后返回一个promise对象。

store.state的作用是将服务端获取到的数据挂载到context对象上，后面在server.js文件里会把这些数据直接发送到浏览器端与客户端的vue实例进行数据(状态)同步。

3、客户端入口文件（entry-client.js）

importVuefrom'vue'import'es6-promise/auto'import{ createApp }from'./main'importProgressBarfrom'./components/ProgressBar.vue'// global progress barconstbar = Vue.prototype.$bar =newVue(ProgressBar).$mount()document.body.appendChild(bar.$el)Vue.mixin({beforeRouteUpdate(to,from,next) {const{ asyncData } =this.$optionsif(asyncData) {Promise.all(asyncData({store:this.$store,route: to})).then(next).catch(next)}else{next()}}})const{ app,router,store } = createApp()if(window.__INITIAL_STATE__) {store.replaceState(window.__INITIAL_STATE__)}router.onReady(() => {router.beforeResolve((to,from,next) => {constmatched = router.getMatchedComponents(to)constprevMatched = router.getMatchedComponents(from)letdiffed =falseconstactivated = matched.filter((c,i) => {returndiffed || (diffed = (prevMatched[i] !== c))})constasyncDataHooks = activated.map(c => c.asyncData).filter(_ => _)if(!asyncDataHooks.length) {returnnext()}bar.start()Promise.all(asyncDataHooks.map(hook => hook({ store,route: to }))).then(() => {bar.finish()next()}).catch(next)})app.$mount('#app')})if('https:'=== location.protocol && navigator.serviceWorker) {navigator.serviceWorker.register('/service-worker.js')}if(window.INITIAL_STATE) {store.replaceState(window.INITIAL_STATE)}

这句的作用是如果服务端的vuex数据发生改变，就将客户端的数据替换掉，保证客户端和服务端的数据同步

Service Worker主要用于拦截并修改访问和资源请求，细粒度地缓存资源。它运行浏览器在后台，运行环境与普通页面脚本不同，所以不能直接参与页面交互。出于安全考虑，service worker只能运行在HTTPS上，防止被人从中攻击。

4、创建服务端渲染器（server.js）

constfs = require('fs')constpath = require('path')constLRU = require('lru-cache')constexpress = require('express')constcompression = require('compression')constresolve= file => path.resolve(__dirname,file)const{ createBundleRenderer } = require('vue-server-renderer')constisProd = process.env.NODE_ENV ==='production'|| process.env.NODE_ENV ==='beta'constuseMicroCache = process.env.MICRO_CACHE !=='false'constserverInfo =`express/${require('express/package.json').version}`+`vue-server-renderer/${require('vue-server-renderer/package.json').version}`constapp = express()consttemplate = fs.readFileSync(resolve('./src/index.template.html'),'utf-8')functioncreateRenderer(bundle,options) {returncreateBundleRenderer(bundle,Object.assign(options,{template,cache: LRU({max:1000,maxAge:1000*60*15}),basedir: resolve('./dist'),runInNewContext:false}))}letrendererletreadyPromiseif(isProd) {constbundle = require('./dist/vue-ssr-server-bundle.json')constclientManifest = require('./dist/vue-ssr-client-manifest.json')renderer = createRenderer(bundle,{clientManifest})}else{readyPromise = require('./build/setup-dev-server')(app,(bundle,options) => {renderer = createRenderer(bundle,options)})}constserve= (path,cache) => express.static(resolve(path),{maxAge: cache && isProd ?1000*60*60*24*30:0})app.use(compression({threshold:0}))app.use('/dist',serve('./dist',true))app.use('/static',serve('./static',true))app.use('/service-worker.js',serve('./dist/service-worker.js'))constmicroCache = LRU({max:100,maxAge:1000})constisCacheable= req => useMicroCachefunctionrender(req,res) {consts = Date.now()res.setHeader("Content-Type","text/html")res.setHeader("Server",serverInfo)consthandleError= err => {if(err.url) {res.redirect(err.url)}else if(err.code ===404) {res.status(404).end('404 | Page Not Found')}else{// Render Error Page or Redirectres.status(500).end('500 | Internal Server Error')console.error(`error during render :${req.url}`)console.error(err.stack)}}constcacheable = isCacheable(req)if(cacheable) {consthit = microCache.get(req.url)if(hit) {if(!isProd) {console.log(`cache hit!`)}returnres.end(hit)}}constcontext = {title:'Vue DB',// default titleurl: req.url}renderer.renderToString(context,(err,html) => {if(err) {returnhandleError(err)}res.end(html)if(cacheable) {microCache.set(req.url,html)}if(!isProd) {console.log(`whole request:${Date.now() - s}ms`)}})}app.get('*',isProd ? render : (req,res) => {readyPromise.then(() => render(req,res))})constport = process.env.PORT ||8888app.listen(port,() => {console.log(`server started at localhost:${port}`)})

5、客户端api文件create-api-client.js

/** * Created by lin on 2017/8/25. */import axios from 'axios';let api;axios.defaults.baseURL = process.env.API_URL;axios.defaults.timeout = 10000;axios.interceptors.response.use((res) => { if (res.status >= 200 && res.status < 300) { return res; } return Promise.reject(res);}, (error) => { return Promise.reject({message: '网络异常，请刷新重试', err: error});});if (process.__API__) { api = process.__API__;} else { api = { get: function(url) { return new Promise((resolve, reject) => { axios.get(url).then(res => { resolve(res); }).catch((error) => { reject(error); }); }); }, post: function(target, options = {}) { return new Promise((resolve, reject) => { axios.post(target, options).then(res => { resolve(res); }).catch((error) => { reject(error); }); }); } };}export default api;

6、服务端api文件create-api-server.js

/** * Created by lin on 2017/8/25. */import axios from 'axios';let cook = process.__COOKIE__ || '';let api;axios.defaults.baseURL = 'https://api.douban.com/v2/';axios.defaults.timeout = 10000;axios.interceptors.response.use((res) => { if (res.status >= 200 && res.status < 300) { return Promise.resolve(res); } return Promise.reject(res);}, (error) => { // 网络异常 return Promise.reject({message: '网络异常，请刷新重试', err: error, type: 1});});if (process.__API__) { api = process.__API__;} else { api = { get: function(target) { return new Promise((resolve, reject) => { axios.request({ url: encodeURI(target), method: 'get', headers: { 'Cookie': cook } }).then(res => { resolve(res); }).catch((error) => { reject(error); }); }); }, post: function(target, options = {}) { return new Promise((resolve, reject) => { axios.request({ url: target, method: 'post', headers: { 'Cookie': cook }, params: options }).then(res => { resolve(res); }).catch((error) => { reject(error); }); }); } };}export default api;

六、那些年遇到的那些坑

问题1、window is not defined

答案1：给用到浏览器对象的地方加if (typeof window !== 'undefined') {}，有一些插件里也用到了浏览器对象，在使用的地方也加一个条件判断：

if (typeofwindow !== 'undefined') {Vue.use(VueAnalytics, {id: process.env.UA_TRACKING_ID,router})}

问题2：用到非Vue系列的插件，如hello.all.js(三方登录的插件)，需要用的地方才引用，报的错和问题1一样。

答案2：这个时候不能再用import导入，需要使用require，

let hello

if (typeof window !== 'undefined') {hello = require('hello')}

问题3：引用bootstrap

答案3：将bootstrap.css和bootstrap.js加入webpack.base.config.js的entry中的vendor中

问题6：bootstap需要jquery，此时把jQuery加在vendor中没用。

答案6：给webpack.base.config.js的plugins添加一个插件，如：

newwebpack.ProvidePlugin({$ : "jquery",jQuery : "jquery","window.jQuery" :"jquery"})

七、例子

https://github.com/linmoer/ssr-vue这是一个服务端渲的例子

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。