BAEL 1793 Adding PageImpl for pagination (#4371)

* BAEL-1793 Spring with Thymeleaf Pagination for a List

* Replace tabs with 4 spaces in HTML based on editor's feedback.

* Updated to use spring data PageImpl for representing paged list

spring-thymeleaf/src/main/java/com/baeldung/thymeleaf/controller/BookController.java

@@ -5,6 +5,10 @@ import java.util.Optional;
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.data.domain.Page;
+import org.springframework.data.domain.PageRequest;
+
 import org.springframework.stereotype.Controller;
 import org.springframework.ui.Model;
 import org.springframework.web.bind.annotation.RequestMapping;
@@ -12,8 +16,7 @@ import org.springframework.web.bind.annotation.RequestMethod;
 import org.springframework.web.bind.annotation.RequestParam;
 
 import com.baeldung.thymeleaf.model.Book;
-import com.baeldung.thymeleaf.model.Page;
-import com.baeldung.thymeleaf.utils.BookUtils;
+import com.baeldung.thymeleaf.service.BookService;
 
 @Controller
 public class BookController {
@@ -21,22 +24,20 @@ public class BookController {
     private static int currentPage = 1;
     private static int pageSize = 5;
 
+    @Autowired
+    private BookService bookService;
+  
     @RequestMapping(value = "/listBooks", method = RequestMethod.GET)
     public String listBooks(Model model, @RequestParam("page") Optional<Integer> page, @RequestParam("size") Optional<Integer> size) {
         page.ifPresent(p -> currentPage = p);
         size.ifPresent(s -> pageSize = s);
 
-        List<Book> books = BookUtils.buildBooks();
-        Page<Book> bookPage = new Page<Book>(books, pageSize, currentPage);
+        Page<Book> bookPage = bookService.findPaginated(PageRequest.of(currentPage - 1, pageSize));
 
-        model.addAttribute("books", bookPage.getList());
-        model.addAttribute("selectedPage", bookPage.getCurrentPage());
-        model.addAttribute("pageSize", pageSize);
+        model.addAttribute("bookPage", bookPage);
 
         int totalPages = bookPage.getTotalPages();
-        model.addAttribute("totalPages", totalPages);
-
-        if (totalPages > 1) {
+        if (totalPages > 0) {
             List<Integer> pageNumbers = IntStream.rangeClosed(1, totalPages)
                 .boxed()
                 .collect(Collectors.toList());

spring-thymeleaf/src/main/java/com/baeldung/thymeleaf/service/BookService.java

@@ -0,0 +1,38 @@
+package com.baeldung.thymeleaf.service;
+
+import java.util.Collections;
+import java.util.List;
+
+import org.springframework.data.domain.Page;
+import org.springframework.data.domain.PageImpl;
+import org.springframework.data.domain.PageRequest;
+import org.springframework.data.domain.Pageable;
+import org.springframework.stereotype.Service;
+
+import com.baeldung.thymeleaf.model.Book;
+import com.baeldung.thymeleaf.utils.BookUtils;
+
+@Service
+public class BookService {
+
+    final private List<Book> books = BookUtils.buildBooks();
+
+    public Page<Book> findPaginated(Pageable pageable) {
+        int pageSize = pageable.getPageSize();
+        int currentPage = pageable.getPageNumber();
+        int startItem = currentPage * pageSize;
+        List<Book> list;
+
+        if (books.size() < startItem) {
+            list = Collections.emptyList();
+        } else {
+            int toIndex = Math.min(startItem + pageSize, books.size());
+            list = books.subList(startItem, toIndex);
+        }
+
+        Page<Book> bookPage = new PageImpl<Book>(list, PageRequest.of(currentPage, pageSize), books.size());
+
+        return bookPage;
+
+    }
+}

spring-thymeleaf/src/main/webapp/WEB-INF/views/listBooks.html

@@ -32,7 +32,7 @@
             </tr>
         </thead>
         <tbody>
-            <tr th:each="book, iStat : ${books}"
+            <tr th:each="book, iStat : ${bookPage.content}"
                 th:style="${iStat.odd}? 'font-weight: bold;'"
                 th:alt-title="${iStat.even}? 'even' : 'odd'">
                 <td th:text="${book.id}" />
@@ -40,11 +40,11 @@
             </tr>
         </tbody>
     </table>
-    <div th:if="${totalPages > 1}" class="pagination"
+    <div th:if="${bookPage.totalPages > 0}" class="pagination"
         th:each="pageNumber : ${pageNumbers}">
-        <a th:href="@{/listBooks(size=${pageSize}, page=${pageNumber})}"
+        <a th:href="@{/listBooks(size=${bookPage.size}, page=${pageNumber})}"
             th:text=${pageNumber}
-            th:class="${pageNumber==selectedPage} ? active"></a>
+            th:class="${pageNumber==bookPage.number + 1} ? active"></a>
     </div>
 
     <div>