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@Component
class AuthTokenHandler {

    @Autowired
    lateinit var authTokenDao: AuthTokenDao

    @Transactional(readOnly = true)
    fun getUserFromToken(token : String?) : User {    
        if (token == null)
            throw AuthenticationException()

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class AuthTokenWebResolver : HandlerMethodArgumentResolver {

    @Autowired
    lateinit var authTokenHandler: AuthTokenHandler

    // to register Auth annotation
    override fun supportsParameter(methodParameter: MethodParameter): Boolean {
        return methodParameter.getParameterAnnotation(Auth::class.java) != null
    }

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@Configuration
class CustomConfig : WebMvcConfigurationSupport() {

    @Bean
    fun authWebArgumentResolverFactory() : HandlerMethodArgumentResolver {
        return AuthWebResolver()
    }

    // Addding the AuthWebResolver to the default argument resolvers
    override fun addArgumentResolvers(argumentResolvers: MutableList<HandlerMethodArgumentResolver>) {

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    @GetMapping("data/{id}")
    fun getData(
            @Auth user : User,
            @PathVariable(value = "id") id: Int
    ) : ResponseEntity<Void> {

        // NOTE: user can be used inside the method body

        // API logic
        

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    @GetMapping("data/{id}")
    fun getData(
            @PathVariable(value = "id") id: Int
    ) : ResponseEntity<Void> {

        // API logic

        return ResponseEntity(HttpStatus.OK)
    }

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@ControllerAdvice
class CustomExceptionsHandler {

    @ExceptionHandler(AuthenticationException::class)
    fun authenticationExceptionHandler(e: Exception): ResponseEntity<String> {
        return ResponseEntity("authToken missing or not valid!", HttpStatus.UNAUTHORIZED)
    }
    
}

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import axios from 'axios';

// sample configurations
const axiosInstance = axios.create({
   withCredentials: true,
   baseURL: 'https://medium.org'
});

export default axiosInstance;

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import axiosInstance from './axiosConfig'

export const Author = {
    getAll: function() {
        return axiosInstance.request({
            method: "GET",
            url: `/api/v1/authors`
        });
    },
    getById: function(authorId) {

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import { Author as AuthorAPI } from './Author'
import { Book as BookAPI } from './Book'

export {
    AuthorAPI,
    BookAPI
}

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import React, {useEffect, useState} from "react";
import {AuthorAPI} from "../../api/index";

function AuthorCard(props) {
    const { authorId } = props;

    const [author, setAuthor] = useState(undefined)

    useEffect(() => {
        AuthorAPI.getById(authorId).then(