task: MVVM design pattern using zkoss framework. (#1678)

* MVVM design pattern using zkoss framework.

* MVVM Design pattern updates for issues reported by SonarCloud.

* MVVM Design pattern updates for coverage issues reported by SonarCloud.

* MVVM Design pattern updates for coverage issues (removing lombok @Data)
reported by SonarCloud.

* MVVM Design pattern updates for coverage issues reported by Sonar - TEST
cases added for Equals and ToString

* MVVM Design Pattern - updating missing/todo details.

* MVVM Design Pattern - adding lombok.config

* MVVM Design Pattern - Removing xml, updating pom.xml and README as per
suggested changes in code review

* Update model-view-viewmodel/README.md

* Update model-view-viewmodel/README.md

* Update model-view-viewmodel/README.md

* Update model-view-viewmodel/README.md

* MVVM Design Pattern - Updated pom.xml and Readme based on Suggested
changes

* added type as xml

* MVVM Design Patterm - root pom.xml and module pom.xml updated

* Update pom.xml

Co-authored-by: Subhrodip Mohanta <hello@subho.xyz>
Co-authored-by: Ilkka Seppälä <iluwatar@users.noreply.github.com>

model-view-viewmodel/src/main/java/com/iluwatar/model/view/viewmodel/Book.java

@@ -0,0 +1,37 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 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.model.view.viewmodel;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+
+@AllArgsConstructor
+@Data
+public class Book {
+
+  private String name;
+  private String author;
+  private String description;
+
+}

model-view-viewmodel/src/main/java/com/iluwatar/model/view/viewmodel/BookService.java

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+package com.iluwatar.model.view.viewmodel;
+
+import java.util.List;
+
+public interface BookService {
+  /* List all books
+   * @return all books
+   */
+  public List<Book> load();
+}

model-view-viewmodel/src/main/java/com/iluwatar/model/view/viewmodel/BookServiceImpl.java

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+package com.iluwatar.model.view.viewmodel;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class BookServiceImpl implements BookService {
+  private List<Book> designPatternBooks = new ArrayList<>();
+
+  /** Initializes Book Data.
+  * To be used and passed along in load method
+  * In this case, list design pattern books are initialized to be loaded.
+  */
+  public BookServiceImpl() {
+    designPatternBooks.add(new Book(
+        "Head First Design Patterns: A Brain-Friendly Guide",
+        "Eric Freeman, Bert Bates, Kathy Sierra, Elisabeth Robson",
+        "Head First Design Patterns Description"));
+    designPatternBooks.add(new Book(
+        "Design Patterns: Elements of Reusable Object-Oriented Software",
+        "Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides",
+        "Design Patterns Description"));
+    designPatternBooks.add(new Book(
+        "Patterns of Enterprise Application Architecture", "Martin Fowler",
+        "Patterns of Enterprise Application Architecture Description"));
+    designPatternBooks.add(new Book(
+        "Design Patterns Explained", "Alan Shalloway, James Trott",
+        "Design Patterns Explained Description"));
+    designPatternBooks.add(new Book(
+        "Applying UML and Patterns: An Introduction to "
+         + "Object-Oriented Analysis and Design and Iterative Development",
+        "Craig Larman", "Applying UML and Patterns Description"));
+  }
+
+  public List<Book> load() {
+    return designPatternBooks;
+  }
+
+}

model-view-viewmodel/src/main/java/com/iluwatar/model/view/viewmodel/BookViewModel.java

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+package com.iluwatar.model.view.viewmodel;
+
+import java.util.List;
+
+import org.zkoss.bind.annotation.Command;
+import org.zkoss.bind.annotation.NotifyChange;
+import org.zkoss.zk.ui.select.annotation.WireVariable;
+
+public class BookViewModel {
+  
+  @WireVariable
+  private List<Book> bookList;
+  private Book selectedBook;
+  private BookService bookService = new BookServiceImpl();
+  
+  public Book getSelectedBook() {
+    return selectedBook;
+  }
+
+  @NotifyChange("selectedBook")
+  public void setSelectedBook(Book selectedBook) {
+    this.selectedBook = selectedBook;
+  }
+
+  public List<Book> getBookList() {
+    return bookService.load();
+  }
+  
+  /** Deleting a book.
+   * When event is triggered on click of Delete button, 
+   * this method will be notified with the selected entry that will be referenced
+   * and used to delete the selected book from the list of books. 
+   */
+  @Command
+  @NotifyChange({"selectedBook","bookList"})
+  public void deleteBook() {
+    if (selectedBook != null) {
+      getBookList().remove(selectedBook);
+      selectedBook = null;
+    }
+  }
+
+}