[使用服务器端渲染访问页面时的ReactJS错误

Question

加载我的ReactJS页面时出现此错误

Error: Invariant failed: You should not use <Switch> outside a <Router>
    at invariant (/home/user/Documents/Development/hmuweb/room/node_modules/tiny-invariant/dist/tiny-invariant.cjs.js:13:11)
    at Object.children (/home/user/Documents/Development/hmuweb/room/node_modules/react-router/cjs/react-router.js:685:19)
    at ReactDOMServerRenderer.render (/home/user/Documents/Development/hmuweb/room/node_modules/react-dom/cjs/react-dom-server.node.development.js:3635:55)
    at ReactDOMServerRenderer.read (/home/user/Documents/Development/hmuweb/room/node_modules/react-dom/cjs/react-dom-server.node.development.js:3373:29)
    at Object.renderToString (/home/user/Documents/Development/hmuweb/room/node_modules/react-dom/cjs/react-dom-server.node.development.js:3988:27)
    at ./server/index.js.app.get (/home/user/Documents/Development/hmuweb/room/server-build/index.js:215:71)
    at Layer.handle [as handle_request] (/home/user/Documents/Development/hmuweb/room/node_modules/express/lib/router/layer.js:95:5)
    at next (/home/user/Documents/Development/hmuweb/room/node_modules/express/lib/router/route.js:137:13)
    at Route.dispatch (/home/user/Documents/Development/hmuweb/room/node_modules/express/lib/router/route.js:112:3)
    at Layer.handle [as handle_request] (/home/user/Documents/Development/hmuweb/room/node_modules/express/lib/router/layer.js:95:5)

我假设此错误消息来自我的App.js文件，但我似乎找不到确切发生错误的位置。我尝试重新构造App.js，但是当我这样做时，我收到另一个错误，说在路由器中将prop历史记录标记为必需，但其值未定义。而且，它无法读取未定义的属性“位置”。您知道如何解决此问题吗？它是在我实现SSR（服务器端渲染）时开始的。

import React, { Component } from 'react';
import { Route, Switch, BrowserRouter as Router } from 'react-router-dom';
import './App.css';
import Room from './App/pages/Room'
import Content from './App/pages/content';

class App extends Component {
  render() {
    return (
      <div>
        <Switch>
          <Route exact={true} path="/" component={Room} />
          <Route path="/watch" component={Content} />
        </Switch>
      </div>
    );
  }
}
export default App;

需要时的webpack.server.js文件

const path = require('path');
const nodeExternals = require('webpack-node-externals');

module.exports = {
  devtool: 'source-map',
  entry: './server/index.js',

  target: 'node',

  externals: [nodeExternals()],

  module: {
    rules: [
      {
        test: /\.js$/,
        use: ["babel-loader"],
        exclude: /node_modules/,
      },
      { test: /\.css$/, loader: "css-loader" },
      { test: /\.(jpg|png|svg)$/, use: 'file-loader'}
    ]
  },
  resolve: {
    alias: {        
        'react-router-dom': path.join('./node_modules/react-router-dom')
    }
  },
  output: {
    path: path.resolve('server-build'),
    filename: 'index.js'
  },

};

需要时的package.json文件

{
  "name": "room",
  "version": "0.1.0",
  "private": true,
  "dependencies": {
    "@babel/plugin-proposal-class-properties": "^7.8.3",
    "axios": "^0.19.2",
    "babel-preset-es2015": "^6.24.1",
    "bootstrap": "^3.4.1",
    "branca": "^0.3.0",
    "cors": "^2.8.5",
    "express": "^4.17.1",
    "hls.js": "^0.13.2",
    "html-react-parser": "^0.10.3",
    "jquery": "^3.5.1",
    "jsonwebtoken": "^8.5.1",
    "object-encrypt-decrypt": "^1.0.2",
    "path": "^0.12.7",
    "react": "^16.13.1",
    "react-dom": "^16.13.1",
    "react-helmet": "^6.0.0",
    "react-router-dom": "^5.2.0",
    "react-router-redux": "^4.0.8",
    "react-scripts": "3.2.0"
  },
  "scripts": {
    "start": "node ./server/index.js | react-scripts start",
    "build": "react-scripts build",
    "test": "react-scripts test",
    "eject": "react-scripts eject",
    "dev:build-server": "NODE_ENV=development webpack --config webpack.server.js --mode=development -w",
    "dev:start": "nodemon ./server-build/index.js",
    "dev": "npm-run-all --parallel build dev:*"
  },
  "eslintConfig": {
    "extends": "react-app"
  },
  "browserslist": {
    "production": [
      ">0.2%",
      "not dead",
      "not op_mini all"
    ],
    "development": [
      "last 1 chrome version",
      "last 1 firefox version",
      "last 1 safari version"
    ]
  },
  "proxy": "http://localhost:5000",
  "devDependencies": {
    "babel-core": "^6.26.3",
    "babel-preset-env": "^1.7.0",
    "babel-preset-react-app": "^9.1.2",
    "nodemon": "^2.0.4",
    "npm-run-all": "^4.1.5",
    "webpack-cli": "^3.3.11",
    "webpack-node-externals": "^1.7.2"
  },
  "babel": {
    "presets": [
      "@babel/preset-env",
      "@babel/preset-react"
    ],
    "plugins": [
      "@babel/plugin-proposal-class-properties"
    ]
  }
}

Index.js

import path from 'path';
import fs from 'fs';
import express from 'express';
import React from 'react'
import ReactDOMServer from 'react-dom/server';
import { StaticRouter } from 'react-router-dom';
import App from '../src/App';
const PORT = process.env.PORT || 5000;
const app = express();

app.use(express.static(path.join(__dirname, '../build')));

app.get('/*', (req, res) => {
  const context = {};
  const app = ReactDOMServer.renderToString(
    <StaticRouter location={req.url} context={context}>
      <App />
    </StaticRouter>
  );
  const indexFile = path.join(__dirname + '../build/index.html');
  fs.readFile(indexFile, 'utf8', (err, data) => {
    if (err) {
      console.error('Something went wrong:', err);
      return res.status(500).send('Oops, better luck next time!');
    }

    if (context.status === 404) {
      res.status(404);
    }

    return res.send(
      data.replace('<div id="root"></div>', `<div id="root">${app}</div>`)
    );
  });
});

app.listen(PORT, () => {
  console.log(`😎 Server is listening on port ${PORT}`);
});

Answer 1

经过数小时的故障排除，我终于解决了这个问题。

代替直接在renderToString函数内部传递，必须将其嵌套在StaticRouter标记内部。