What is SSR? How to implement SSR server-side rendering in vue?

What is SSR? The following article will introduce to you how to implement SSR server-side rendering in vue. I hope it will be helpful to you!

1. What is SSR

Server-Side Rendering We call it SSR , meaning server-side rendering

refers to the page processing technology that completes the HTML structure splicing of the page on the server side, sends it to the browser, and then binds status and events to it. The process of becoming a fully interactive page. [Related recommendations: vuejs video tutorial]

Let’s first take a look at the development history of Web in three stages:

• Traditional server Rendering SSR
• Single page application SPA
• Server-side rendering SSR

Traditional web development

Web page content is served End-side rendering is completed and transferred to the browser in one go

Open the page to view the source code. What the browser gets is the entire dom structure

Single Page Application SPA

The excellent user experience of single page applications has gradually made it become mainstream. The page content is rendered by JS. This method is called Render for the client

#Open the page to view the source code, the browser only gets the host element#app, and no content

Server-side rendering SSR

SSRSolution, the backend renders the complete first screen dom structure return, the front end gets it The content includes the first screen and the complete spa structure. After the application is activated, it will still run in the spa way

After reading the front-end development, we Let’s take a look at Vue’s official explanation of SSR:

Vue.js is a framework for building client applications. By default, Vue components can be output in the browser to generate DOM and manipulate DOM. However, it is also possible to render the same components as server-side HTML strings, send them directly to the browser, and finally "activate" these static tags into a fully interactive application on the client

Server Rendering Vue.js applications can also be considered "isomorphic" or "universal" because most of the application's code can run on both the server and the client

We get it from Home Explained The following conclusions:

• Vue SSR is an improved server-side rendering on SPA
Vue SSR
• The rendered page needs to be activated on the client to achieve interaction
Vue SSR
• will contain two parts: the first screen rendered by the server, and the interactive SPA

2. What is solved

SSR mainly solves the following two problems:

seo: search engine priority crawling Take the page

HTML
• structure and use ssr, the server has already generated the HTML associated with the business, which is beneficial to seoFirst screen rendering: Users can see the page view without waiting for all
js
• of the page to be loaded (the pressure comes to the server, so it is necessary to weigh which should be rendered on the server side and which should be left to the client)
But using

SSR

also has the following shortcomings:

Complexity: the complexity of the entire project
Library support, code compatibility
Performance issues

• Each request is
  n
  • instances Creation, otherwise it will be polluted and the consumption will become very large cache
  node serve
  • , nginx determine whether the current user has expired, and cache it if it has not expired , use the result just now. Downgrade: Monitor
  cpu
  • , if the memory usage is too much, spa, return a single shell
The server load increases. Compared with the front-end and back-end separated servers that only need to provide static resources, the server load is greater, so we must use it carefully
So when we choose whether to use

Before SSR

, we need to carefully ask ourselves these questions:

Are there only a few pages that require
• SEO

  , and can these use pre-rendering ( How Implementation

  For isomorphic development, we still use
webpack
• for packaging. We have to solve two problems: server-side first screen rendering and client-side activation

  Here you need to generate a serverbundle file for server first screen rendering and a clientbundle file for client activation

  

  Except for two different entrances, the code structure is exactly the same as the previous vueapplication

  src
  ├── router
  ├────── index.js # 路由声明
  ├── store
  ├────── index.js # 全局状态
  ├── main.js # ⽤于创建vue实例
  ├── entry-client.js # 客户端⼊⼝，⽤于静态内容“激活”
  └── entry-server.js # 服务端⼊⼝，⽤于⾸屏内容渲染

  Routing configuration

  import Vue from "vue"; import Router from "vue-router"; Vue.use(Router);
  //导出⼯⼚函数
  export function createRouter(){
      return new Router({
      mode: 'history',
      routes: [
         // 客户端没有编译器，这⾥要写成渲染函数
          { path: "/", component: { render: h => h('div', 'index page') } },
          { path: "/detail", component: { render: h => h('div', 'detail page') }}
      ]
    });
   }

  Main file main.js

  Different from before, the main file is the factory responsible for creating vue instances. Each request will have an independent vue instance created

  import Vue from "vue";
  import App from "./App.vue";
  import { createRouter } from "./router";
  // 导出Vue实例⼯⼚函数，为每次请求创建独⽴实例
  // 上下⽂⽤于给vue实例传递参数
  export function createApp(context) {
      const router = createRouter();
      const app = new Vue({ router, context, render: h => h(App) });
      return { app, router };
    }

  Write the server entry src/entry-server.js

  Its task is to create a Vue instance and specify the first screen based on the incoming url

  import { createApp } from "./main";
  // 返回⼀个函数，接收请求上下⽂，返回创建的vue实例
  export default context => {
  // 这⾥返回⼀个Promise，确保路由或组件准备就绪
      return new Promise((resolve, reject) => {
          const { app, router } = createApp(context);
          // 跳转到⾸屏的地址
          router.push(context.url);
          // 路由就绪，返回结果
          router.onReady(() => {
          resolve(app);
          }, reject);
      });
  };

  Writing the client entryentry-client.js

  The client entry only needs to create the vue instance and perform mounting. This step Called activation

  import { createApp } from "./main";
  // 创建vue、router实例
  const { app, router } = createApp();
  // 路由就绪，执⾏挂载
  router.onReady(() => { app.$mount("#app"); });

  Configurewebpack

  Install dependencies

  npm install webpack-node-externals lodash.merge -D

  Configure vue.config.js

  // 两个插件分别负责打包客户端和服务端
  const VueSSRServerPlugin = require("vue-server-renderer/server-plugin");
  const VueSSRClientPlugin = require("vue-server-renderer/client-plugin");
  const nodeExternals = require("webpack-node-externals");
  const merge = require("lodash.merge");
  // 根据传⼊环境变量决定⼊⼝⽂件和相应配置项
  const TARGET_NODE = process.env.WEBPACK_TARGET === "node";
  const target = TARGET_NODE ? "server" : "client";
  module.exports = {
      css: {
          extract: false
      },
      outputDir: './dist/'+target,
      configureWebpack: () => ({
          // 将 entry 指向应⽤程序的 server / client ⽂件
          entry: `./src/entry-${target}.js`,
          // 对 bundle renderer 提供 source map ⽀持
          devtool: 'source-map',
          // target设置为node使webpack以Node适⽤的⽅式处理动态导⼊，
          // 并且还会在编译Vue组件时告知`vue-loader`输出⾯向服务器代码。
          target: TARGET_NODE ? "node" : "web",
          // 是否模拟node全局变量
          node: TARGET_NODE ? undefined : false,
          output: {
              // 此处使⽤Node⻛格导出模块
              libraryTarget: TARGET_NODE ? "commonjs2" : undefined
          },
          // https://webpack.js.org/configuration/externals/#function
          // https://github.com/liady/webpack-node-externals
          // 外置化应⽤程序依赖模块。可以使服务器构建速度更快，并⽣成较⼩的打包⽂件。
          externals: TARGET_NODE
          ? nodeExternals({
              // 不要外置化webpack需要处理的依赖模块。
              // 可以在这⾥添加更多的⽂件类型。例如，未处理 *.vue 原始⽂件，
              // 还应该将修改`global`（例如polyfill）的依赖模块列⼊⽩名单
              whitelist: [/\.css$/]
          })
          : undefined,
          optimization: {
              splitChunks: undefined
          },
          // 这是将服务器的整个输出构建为单个 JSON ⽂件的插件。
          // 服务端默认⽂件名为 `vue-ssr-server-bundle.json`
          // 客户端默认⽂件名为 `vue-ssr-client-manifest.json`。
          plugins: [TARGET_NODE ? new VueSSRServerPlugin() : new
                    VueSSRClientPlugin()]
      }),
      chainWebpack: config => {
          // cli4项⽬添加
          if (TARGET_NODE) {
              config.optimization.delete('splitChunks')
          }
  
          config.module
              .rule("vue")
              .use("vue-loader")
              .tap(options => {
              merge(options, {
                  optimizeSSR: false
              });
          });
      }
  };

  Configure the script and install dependencies

  npm i cross-env - D

  "scripts": {
   "build:client": "vue-cli-service build",
   "build:server": "cross-env WEBPACK_TARGET=node vue-cli-service build",
   "build": "npm run build:server && npm run build:client"
  }

  Execute packaging: npm run build

  Last modification of the host file/public/index.html

  <!DOCTYPE html>
  <html>
      <head>
          <meta charset="utf-8">
          <meta http-equiv="X-UA-Compatible" content="IE=edge">
          <meta name="viewport" content="width=device-width,initial-scale=1.0">
          <title>Document</title>
      </head>
      <body>
          <!--vue-ssr-outlet-->
      </body>
  </html>

  is the server-side rendering entry location. Be careful not to add spaces before and after it for the sake of appearance.

  Installationvuex

  npm install -S vuex

  Create vuexFactory function

  import Vue from 'vue'
  import Vuex from 'vuex'
  Vue.use(Vuex)
  export function createStore () {
      return new Vuex.Store({
          state: {
              count:108
          },
          mutations: {
              add(state){
                  state.count += 1;
              }
          }
      })
  }

  Mount in main.js filestore

  import { createStore } from './store'
  export function createApp (context) {
      // 创建实例
      const store = createStore()
      const app = new Vue({
          store, // 挂载
          render: h => h(App)
      })
      return { app, router, store }
  }

  Server-side rendering is a "snapshot" of the application. If the application relies on some asynchronous data, then the data needs to be prefetched and parsed before starting rendering

  InstorePerform one-step data acquisition

  export function createStore() {
      return new Vuex.Store({
          mutations: {
              // 加⼀个初始化
              init(state, count) {
                  state.count = count;
              },
          },
          actions: {
              // 加⼀个异步请求count的action
              getCount({ commit }) {
                  return new Promise(resolve => {
                      setTimeout(() => {
                          commit("init", Math.random() * 100);
                          resolve();
                      }, 1000);
                  });
              },
          },
      });
  }

  Data prefetch logic in the component

  export default {
      asyncData({ store, route }) { // 约定预取逻辑编写在预取钩⼦asyncData中
          // 触发 action 后，返回 Promise 以便确定请求结果
          return store.dispatch("getCount");
      }
  };

  Server-side data prefetch, entry-server.js

  import { createApp } from "./app";
  export default context => {
      return new Promise((resolve, reject) => {
          // 拿出store和router实例
          const { app, router, store } = createApp(context);
          router.push(context.url);
          router.onReady(() => {
              // 获取匹配的路由组件数组
              const matchedComponents = router.getMatchedComponents();
  
              // 若⽆匹配则抛出异常
              if (!matchedComponents.length) {
                  return reject({ code: 404 });
              }
  
              // 对所有匹配的路由组件调⽤可能存在的`asyncData()`
              Promise.all(
                  matchedComponents.map(Component => {
                      if (Component.asyncData) {
                          return Component.asyncData({
                              store,
                              route: router.currentRoute,
                          });
                      }
                  }),
              )
                  .then(() => {
                  // 所有预取钩⼦ resolve 后，
                  // store 已经填充⼊渲染应⽤所需状态
                  // 将状态附加到上下⽂，且 `template` 选项⽤于 renderer 时，
                  // 状态将⾃动序列化为 `window.__INITIAL_STATE__`，并注⼊ HTML
                  context.state = store.state;
  
                  resolve(app);
              })
                  .catch(reject);
          }, reject);
      });
  };

  Before the client is mounted to the application, store should obtain the status, entry-client.js

  // 导出store
  const { app, router, store } = createApp();
  // 当使⽤ template 时，context.state 将作为 window.__INITIAL_STATE__ 状态⾃动嵌⼊到最终的 HTML
  // 在客户端挂载到应⽤程序之前，store 就应该获取到状态：
  if (window.__INITIAL_STATE__) {
      store.replaceState(window.__INITIAL_STATE__);
  }

  Client data prefetching Processing, main.js

  Vue.mixin({
      beforeMount() {
          const { asyncData } = this.$options;
          if (asyncData) {
              // 将获取数据操作分配给 promise
              // 以便在组件中，我们可以在数据准备就绪后
              // 通过运⾏ `this.dataPromise.then(...)` 来执⾏其他任务
              this.dataPromise = asyncData({
                  store: this.$store,
                  route: this.$route,
              });
          }
      },
  });

  Modify the server startup file

  // 获取⽂件路径
  const resolve = dir => require('path').resolve(__dirname, dir)
  // 第 1 步：开放dist/client⽬录，关闭默认下载index⻚的选项，不然到不了后⾯路由
  app.use(express.static(resolve('../dist/client'), {index: false}))
  // 第 2 步：获得⼀个createBundleRenderer
  const { createBundleRenderer } = require("vue-server-renderer");
  // 第 3 步：服务端打包⽂件地址
  const bundle = resolve("../dist/server/vue-ssr-server-bundle.json");
  // 第 4 步：创建渲染器
  const renderer = createBundleRenderer(bundle, {
      runInNewContext: false, // https://ssr.vuejs.org/zh/api/#runinnewcontext
      template: require('fs').readFileSync(resolve("../public/index.html"), "utf8"), // 宿主⽂件
      clientManifest: require(resolve("../dist/client/vue-ssr-clientmanifest.json")) // 客户端清单
  });
  app.get('*', async (req,res)=>{
      // 设置url和title两个重要参数
      const context = {
          title:'ssr test',
          url:req.url
      }
      const html = await renderer.renderToString(context);
      res.send(html)
  })

  Summary

  • UsessrThere is no singleton mode. Each user request will create a new vue instance

  • implementationssrrequired Realize server-side first screen rendering and client activation

  • Server-side asynchronous data acquisitionasyncData can be divided into first screen asynchronous acquisition and switching component acquisition

    • The first screen obtains data asynchronously, which should have been completed during server-side pre-rendering
    • The switching component is mixed in through mixin, and the data acquisition is completed through the beforeMount hook

  (Learning video sharing: vuejs tutorial, web front-end)

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