/* * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt). * * The MIT License * Copyright © 2014-2022 Ilkka Seppälä * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to deal * in the Software without restriction, including without limitation the rights * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell * copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in * all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN * THE SOFTWARE. */ package com.iluwatar.dynamicproxy; import java.lang.reflect.Proxy; import java.net.http.HttpClient; import lombok.extern.slf4j.Slf4j; /** * Application to demonstrate the Dynamic Proxy pattern. This application allow us to hit the public * fake API https://jsonplaceholder.typicode.com for the resource Album through an interface. * The call to Proxy.newProxyInstance creates a new dynamic proxy for the AlbumService interface and * sets the AlbumInvocationHandler class as the handler to intercept all the interface's methods. * Everytime that we call an AlbumService's method, the handler's method "invoke" will be call * automatically, and it will pass all the method's metadata and arguments to other specialized * class - TinyRestClient - to prepare the Rest API call accordingly. * In this demo, the Dynamic Proxy pattern help us to run business logic through interfaces without * an explicit implementation of the interfaces and supported on the Java Reflection approach. */ @Slf4j public class App { static final String REST_API_URL = "https://jsonplaceholder.typicode.com"; private String baseUrl; private HttpClient httpClient; private AlbumService albumServiceProxy; /** * Class constructor. * * @param baseUrl Root url for endpoints. * @param httpClient Handle the http communication. */ public App(String baseUrl, HttpClient httpClient) { this.baseUrl = baseUrl; this.httpClient = httpClient; } /** * Application entry point. * * @param args External arguments to be passed. Optional. */ public static void main(String[] args) { App app = new App(App.REST_API_URL, HttpClient.newHttpClient()); app.createDynamicProxy(); app.callMethods(); } /** * Create the Dynamic Proxy linked to the AlbumService interface and to the AlbumInvocationHandler. */ public void createDynamicProxy() { AlbumInvocationHandler albumInvocationHandler = new AlbumInvocationHandler(baseUrl, httpClient); albumServiceProxy = (AlbumService) Proxy.newProxyInstance( App.class.getClassLoader(), new Class[]{AlbumService.class}, albumInvocationHandler); } /** * Call the methods of the Dynamic Proxy, in other words, the AlbumService interface's methods * and receive the responses from the Rest API. */ public void callMethods() { int albumId = 17; int userId = 3; var albums = albumServiceProxy.readAlbums(); albums.forEach(album -> LOGGER.info("{}", album)); var album = albumServiceProxy.readAlbum(albumId); LOGGER.info("{}", album); var newAlbum = albumServiceProxy.createAlbum(Album.builder() .title("Big World").userId(userId).build()); LOGGER.info("{}", newAlbum); var editAlbum = albumServiceProxy.updateAlbum(albumId, Album.builder() .title("Green Valley").userId(userId).build()); LOGGER.info("{}", editAlbum); var removedAlbum = albumServiceProxy.deleteAlbum(albumId); LOGGER.info("{}", removedAlbum); } }