BAEL-305: Refactored Book and Bookshelf as interfaces and implemented them.

enterprise-patterns/front-controller-pattern/pom.xml

@@ -17,7 +17,7 @@
         <dependency>
             <groupId>javax.servlet</groupId>
             <artifactId>javax.servlet-api</artifactId>
-            <version>3.1.0</version>
+            <version>4.0.0-b01</version>
             <scope>provided</scope>
         </dependency>
     </dependencies>

enterprise-patterns/front-controller-pattern/src/main/java/com/baeldung/enterprise/patterns/front/controller/commands/SearchCommand.java

@@ -1,7 +1,7 @@
 package com.baeldung.enterprise.patterns.front.controller.commands;
 
 import com.baeldung.enterprise.patterns.front.controller.data.Book;
-import com.baeldung.enterprise.patterns.front.controller.data.Bookshelf;
+import com.baeldung.enterprise.patterns.front.controller.data.BookshelfImpl;
 
 import javax.servlet.ServletException;
 import java.io.IOException;
@@ -9,13 +9,12 @@ import java.io.IOException;
 public class SearchCommand extends FrontCommand {
     @Override
     public void process() throws ServletException, IOException {
-        Book book = Bookshelf.getInstance()
+        Book book = new BookshelfImpl().getInstance()
           .findByTitle(request.getParameter("title"));
         if (book != null) {
             request.setAttribute("book", book);
             forward("book-found");
         } else {
-            request.setAttribute("books", Bookshelf.getInstance().getBooks());
             forward("book-notfound");
         }
     }

enterprise-patterns/front-controller-pattern/src/main/java/com/baeldung/enterprise/patterns/front/controller/data/Book.java

@@ -1,40 +1,15 @@
 package com.baeldung.enterprise.patterns.front.controller.data;
 
-public class Book {
+public interface Book {
-    private String author;
+    String getAuthor();
-    private String title;
-    private Double price;
 
-    public Book() {
+    void setAuthor(String author);
-    }
 
-    public Book(String author, String title, Double price) {
+    String getTitle();
-        this.author = author;
-        this.title = title;
-        this.price = price;
-    }
 
-    public String getAuthor() {
+    void setTitle(String title);
-        return author;
-    }
 
-    public void setAuthor(String author) {
+    Double getPrice();
-        this.author = author;
-    }
 
-    public String getTitle() {
+    void setPrice(Double price);
-        return title;
-    }
-
-    public void setTitle(String title) {
-        this.title = title;
-    }
-
-    public Double getPrice() {
-        return price;
-    }
-
-    public void setPrice(Double price) {
-        this.price = price;
-    }
 }

enterprise-patterns/front-controller-pattern/src/main/java/com/baeldung/enterprise/patterns/front/controller/data/BookImpl.java

@@ -0,0 +1,46 @@
+package com.baeldung.enterprise.patterns.front.controller.data;
+
+public class BookImpl implements Book {
+    private String author;
+    private String title;
+    private Double price;
+
+    public BookImpl() {
+    }
+
+    public BookImpl(String author, String title, Double price) {
+        this.author = author;
+        this.title = title;
+        this.price = price;
+    }
+
+    @Override
+    public String getAuthor() {
+        return author;
+    }
+
+    @Override
+    public void setAuthor(String author) {
+        this.author = author;
+    }
+
+    @Override
+    public String getTitle() {
+        return title;
+    }
+
+    @Override
+    public void setTitle(String title) {
+        this.title = title;
+    }
+
+    @Override
+    public Double getPrice() {
+        return price;
+    }
+
+    @Override
+    public void setPrice(Double price) {
+        this.price = price;
+    }
+}

enterprise-patterns/front-controller-pattern/src/main/java/com/baeldung/enterprise/patterns/front/controller/data/Bookshelf.java

@@ -1,32 +1,15 @@
 package com.baeldung.enterprise.patterns.front.controller.data;
 
-import java.util.ArrayList;
+public interface Bookshelf {
-import java.util.List;
 
-public class Bookshelf {
+    default void init() {
-    private static Bookshelf INSTANCE = new Bookshelf();
+        add(new BookImpl("Wilson, Robert Anton & Shea, Robert", "Illuminati", 9.99));
-    private List<Book> books = new ArrayList<>();
+        add(new BookImpl("Fowler, Martin", "Patterns of Enterprise Application Architecture", 27.88));
-
-    public static Bookshelf getInstance() {
-        if (INSTANCE.books.size() == 0) {
-            INSTANCE.init();
-        }
-        return INSTANCE;
     }
 
-    private void init() {
+    Bookshelf getInstance();
-        books.add(new Book("Wilson, Robert Anton & Shea, Robert", "Illuminati", 9.99));
-        books.add(new Book("Fowler, Martin", "Patterns of Enterprise Application Architecture", 27.88));
-    }
 
-    public Book findByTitle(String title) {
+    <E extends Book> boolean add(E book);
-        return books.stream()
-          .filter(book -> book.getTitle().toLowerCase().contains(title.toLowerCase()))
-          .findFirst()
-          .orElse(null);
-    }
 
-    public List<Book> getBooks() {
+    Book findByTitle(String title);
-        return books;
-    }
 }

enterprise-patterns/front-controller-pattern/src/main/java/com/baeldung/enterprise/patterns/front/controller/data/BookshelfImpl.java

@@ -0,0 +1,24 @@
+package com.baeldung.enterprise.patterns.front.controller.data;
+
+import java.util.ArrayList;
+
+public class BookshelfImpl extends ArrayList<Book> implements Bookshelf {
+    private static Bookshelf INSTANCE;
+
+    @Override
+    public Bookshelf getInstance() {
+        if (INSTANCE == null) {
+            INSTANCE = new BookshelfImpl();
+            INSTANCE.init();
+        }
+        return INSTANCE;
+    }
+
+    @Override
+    public Book findByTitle(String title) {
+        return this.stream()
+          .filter(book -> book.getTitle().toLowerCase().contains(title.toLowerCase()))
+          .findFirst()
+          .orElse(null);
+    }
+}