feature: #2542 Dynamic proxy pattern (#2814)

* #2542 First commit * #2542 Fixing comments * #2542 Refactoring code * #2542 Update Readme * #2542 Add mockito dependencies * #2542 Add unit test * #2542 Fixes for testing * #2542 Fixing typos * #2542 Fixing SonarLint issues * #2542 Fixing code review --------- Co-authored-by: Sashir Estela <sashirestela@yahoo.com> Co-authored-by: Ilkka Seppälä <iluwatar@users.noreply.github.com>
2026-05-16 00:59:02 +00:00 · 2024-03-23 05:34:32 -05:00
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+/*
+ * 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);
+  }
+
+}