index.js

import React from 'react';
import ReactDOM from 'react-dom';
import './css/reset.css';
import './css/timeline.css';
import './css/login.css';
import { BrowserRouter, Route } from 'react-router-dom';
import App from './App';
import Login from './components/Login';
import Logout from './components/Logout';


const PrivateRoute = ({ component: Component, ...rest }) => (
  <Route {...rest} render={(props) => (
    localStorage.getItem('auth-token') === null
      ? <Login msg='Você precisa estar logado para acessar esse endereço' />
      : <App />
  )} />
)


ReactDOM.render(
    (
        <BrowserRouter>
          <div>
            <Route exact path="/" component={Login}  />
            <Route path="/" component={Logout}  />
            <PrivateRoute path="/timeline" component={App} />
          </div>
        </BrowserRouter>
    ),
    document.getElementById('root')
);

Login.js

import React, { Component } from 'react';

export default class Login extends Component {

    constructor (props) {
        super(props);
        console.log(this.props.redirectLogin);
        this.state = { msg: this.props.msg };
    }
    

    handleSubmit(event) {
      event.preventDefault();

      const requestInfo = {
        method: 'POST',
        body: JSON.stringify({
            login: this.login.value,
            senha: this.senha.value
        }),
        headers: new Headers({
            'Content-type': 'application/json'
        }) 
      };

      fetch('http://localhost:8080/api/public/login', requestInfo)
        .then(response => {
            if(response.ok){
                return response.text();
            }else{
              throw new Error('Não foi possível fazer o login.');
            }
        })
        .then( token => {
            localStorage.setItem('auth-token', token);
            this.props.history.push('/timeline');
        })
        .catch(error => {
            this.setState({msg: error.message })
        })
    }

    render() {
        return (
            <div className="login-box">
                <h1 className="header-logo">Instalura</h1>
                <span>{this.state.msg}</span>
                <form onSubmit={this.handleSubmit.bind(this)}>
                    <input type="text" ref={(input) => this.login = input}/>
                    <input type="password" ref={(input) => this.senha = input}/>
                    <input type="submit" value="login"/>
                </form>
            </div>
        )
    }
}