我是第一次使用路由器..如何使路由在第一个组件打开时自动渲染它？

import React from 'react';
import { BrowserRouter as Router, Route, Link } from 'react-router-dom';

// 定义组件
const Home = () => <h2>首页</h2>;
const About = () => <h2>关于</h2>;
const Contact = () => <h2>联系我们</h2>;

// 创建顶层组件
const App = () => {
  return (
    <Router>
      <div>
        <nav>
          <ul>
            <li>
              <Link to="/">首页</Link>
            </li>
            <li>
              <Link to="/about">关于</Link>
            </li>
            <li>
              <Link to="/contact">联系我们</Link>
            </li>
          </ul>
        </nav>

        <Route path="/" exact component={Home} />
        <Route path="/about" component={About} />
        <Route path="/contact" component={Contact} />
      </div>
    </Router>
  );
};

export default App;