feature: #1299 Add Identity Map Pattern (#2094)

* #1299 IMPLEMENT IDENTITY MAP PATTERN. * #1299 Add docstrings, README, testCases and class diagram. * #1299 Update a comment string in DB implementation. * #1299 Fix code smells. * #1299 Fix code smells and add comments to App.java * #1299 Update constant name. * #1299 Remove java version dependency and update README.md. * #1299 Add lombok to PersonFinder.java. * #1299 Add dependency to maven-assembly-plugin. * #1299 Use java streams in PersonDbSimulatorImplementation.java. * #1299 Add print statements while returning the person object. * #1299 Update README.md. * #1299 Add puml file. * Update README.md
2026-05-16 06:58:54 +00:00 · 2022-11-10 06:55:44 +11:00
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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.identitymap;
+
+import lombok.extern.slf4j.Slf4j;
+
+/**
+ * The basic idea behind the Identity Map is to have a series of maps containing objects that have been pulled from the database.
+ * The below example demonstrates the identity map pattern by creating a sample DB.
+ * Since only 1 DB has been created we only have 1 map corresponding to it for the purpose of this demo.
+ * When you load an object from the database, you first check the map.
+ * If there’s an object in it that corresponds to the one you’re loading, you return it. If not, you go to the database,
+ * putting the objects on the map for future reference as you load them.
+ */
+@Slf4j
+public class App {
+  /**
+   * Program entry point.
+   *
+   * @param args command line args.
+   */
+  public static void main(String[] args) {
+
+    // Dummy Persons
+    Person person1 = new Person(1, "John", 27304159);
+    Person person2 = new Person(2, "Thomas", 42273631);
+    Person person3 = new Person(3, "Arthur", 27489171);
+    Person person4 = new Person(4, "Finn", 20499078);
+    Person person5 = new Person(5, "Michael", 40599078);
+
+    // Init database
+    PersonDbSimulatorImplementation db = new PersonDbSimulatorImplementation();
+    db.insert(person1);
+    db.insert(person2);
+    db.insert(person3);
+    db.insert(person4);
+    db.insert(person5);
+
+    // Init a personFinder
+    PersonFinder finder = new PersonFinder();
+    finder.setDb(db);
+
+    // Find persons in DataBase not the map.
+    LOGGER.info(finder.getPerson(2).toString());
+    LOGGER.info(finder.getPerson(4).toString());
+    LOGGER.info(finder.getPerson(5).toString());
+    // Find the person in the map.
+    LOGGER.info(finder.getPerson(2).toString());
+
+  }
+}