使用react-router4.0实现重定向和404功能

import React, { Component } from 'react';
import axios from 'axios';
import { Redirect } from 'react-router-dom';

class Login extends Component{
  constructor(){
    super();
    this.state = {value: '', logined: false};
    this.handleChange = this.handleChange.bind(this);
    this.toLogin = this.toLogin.bind(this);
  }
  handleChange(event) {
    this.setState({value: event.target.value})
  }

  toLogin(accesstoken) {
    axios.post('yoururl',{accesstoken})
      .then((res) => {
        this.setState({logined: true});
      })
  }

  render() {
    if(this.props.logined) {
      return (
        <Redirect to="/user"/>
      )
    }
    return (
      <div>
          <input type="text" value={this.state.value} onChange={this.handleChange} />
          <a onClick={() => { this.toLogin(this.state.value) }}>登录</a>
      </div>
    )
  }
}

export default Login;

const LOGIN_SUCCESS = 'LOGIN_SUCCESS';
const LOGIN_FAILED = 'LOGIN_FAILED';
const LOGINOUT = 'LOGINOUT';

const Login = function(state, action) {
  if(!state) {
    console.log('state');
    if(sessionStorage.getItem('usermsg')) {
      return {
        logined: true,
        usermsg: JSON.parse(sessionStorage.getItem('usermsg'))
      }
    }
    return {
      logined: false,
      usermsg: {}
    }
  }
  switch(action.type) {
    case LOGIN_SUCCESS:
      return {logined: true,usermsg: action.usermsg};
    case LOGIN_FAILED:
      return {logined: false,usermsg:{}};
    case LOGINOUT:
      return {logined: false, usermsg: {}};
    default:
      return state
  }
};

export  default Login;

<Switch>
  <Route path="/" exact component={Home}/>
  <Route path="/user" component={User}/>
  <Route component={NoMatch}/>
</Switch>