src/main/java/com/primefactorsolutions/service/EmployeeService.java

@@ -6,6 +6,7 @@ import org.springframework.data.domain.Page;
 import org.springframework.data.domain.PageRequest;
 import org.springframework.data.domain.Pageable;
 import lombok.Data;
+import org.springframework.data.domain.Sort;
 import org.springframework.stereotype.Service;
 
 import java.util.List;
@@ -33,13 +34,13 @@ public class EmployeeService {
         return null;
     }
 
-    public Page<Employee> getEmployeesPaginated(int pageNo, int pageSize) {
-        Pageable pageable = PageRequest.of(pageNo - 1, pageSize);
+    public Page<Employee> getEmployeesPaginated(int pageNo, int pageSize, String sortField, boolean ascending) {
+        Sort sort = ascending ? Sort.by(sortField).ascending() : Sort.by(sortField).descending();
+        Pageable pageable = PageRequest.of(pageNo - 1, pageSize, sort);
         return employeeRepository.findAll(pageable);
     }
 
-    public boolean hasNextPage(int currentPage, int pageSize) {
-        Page<Employee> page = getEmployeesPaginated(currentPage, pageSize);
-        return page.hasNext();
+    public boolean hasNextPage(int currentPage, int pageSize, String sortField, boolean ascending) {
+        return getEmployeesPaginated(currentPage, pageSize, sortField, ascending).hasNext();
     }
 }

src/main/java/com/primefactorsolutions/views/EmployeesListView.java

@@ -2,15 +2,11 @@ package com.primefactorsolutions.views;
 
 import com.primefactorsolutions.model.Employee;
 import com.primefactorsolutions.service.EmployeeService;
-import com.vaadin.flow.component.ClickEvent;
-import com.vaadin.flow.component.Component;
-import com.vaadin.flow.component.ComponentEventListener;
 import com.vaadin.flow.component.button.Button;
 import com.vaadin.flow.component.combobox.ComboBox;
 import com.vaadin.flow.component.html.H2;
 import com.vaadin.flow.component.html.Main;
 import com.vaadin.flow.component.orderedlayout.HorizontalLayout;
-import com.vaadin.flow.function.ValueProvider;
 import com.vaadin.flow.router.PageTitle;
 import com.vaadin.flow.router.Route;
 import com.vaadin.flow.spring.annotation.SpringComponent;
@@ -25,77 +21,103 @@ import org.springframework.data.domain.Page;
 @Route(value = "/employees", layout = MainLayout.class)
 @PermitAll
 public class EmployeesListView extends Main {
-    private final EmployeeService employeeService;
-    private int currentPage = 1;
-    private final int pageSize = 5;
-    private final Button previous;
-    private final Button next;
 
-    public EmployeesListView(final EmployeeService employeeService) {
+    private final EmployeeService employeeService;
+    private final int pageSize = 5;
+    private int currentPage = 1;
+    private String sortField = "firstName";
+    private boolean ascending = true;
+    private VGrid<Employee> grid;
+    private Button previous;
+    private Button next;
+
+    public EmployeesListView(EmployeeService employeeService) {
         this.employeeService = employeeService;
+        addComponents();
+        updateGrid();
+    }
+
+    private void addComponents() {
+        addTitle();
+        addOrderButtons();
+        configureGrid();
+        addNavigationButtons();
+    }
+
+    private void addTitle() {
         final H2 title = new H2("Employees list");
+        add(title);
+    }
+
+    private void addOrderButtons() {
         final HorizontalLayout hl = new HorizontalLayout();
-        final HorizontalLayout hf = new HorizontalLayout();
-        final Button employeeListAscendingOrder  = new Button("Employee List in Ascending Order");
-        employeeListAscendingOrder.addClickListener((ComponentEventListener<ClickEvent<Button>>) buttonClickEvent -> {
-            // no-op
+        hl.add(createOrderButton("Employee List in Ascending Order", true));
+        hl.add(createOrderButton("Employee List in Descending Order", false));
+        add(hl);
+    }
+
+    private Button createOrderButton(String label, boolean isAscending) {
+        Button button = new Button(label);
+        button.addClickListener(event -> {
+            sortField = "firstName";
+            ascending = isAscending;
+            updateGrid();
         });
-        hl.add(employeeListAscendingOrder);
-        final Button employeeListDescendingOrder  = new Button("Employee List in Descending Order");
-        employeeListDescendingOrder.addClickListener((ComponentEventListener<ClickEvent<Button>>) buttonClickEvent -> {
-            // no-op
-        });
-        hl.add(employeeListDescendingOrder);
-        final VGrid<Employee> grid = new VGrid<>(Employee.class);
+        return button;
+    }
+    private void configureGrid() {
+        grid = new VGrid<>(Employee.class);
         grid.setColumns("firstName", "lastName", "status");
         grid.setAllRowsVisible(true);
-        grid.addComponentColumn((ValueProvider<Employee, Component>) employee -> {
+        grid.addComponentColumn(employee -> createStatusComboBox()).setHeader("Change Status");
+        grid.addComponentColumn(employee -> createEditButton());
+        grid.addComponentColumn(employee -> createSaveButton());
+        add(grid);
+    }
+
+    private ComboBox<String> createStatusComboBox() {
         ComboBox<String> statusComboBox = new ComboBox<>();
         statusComboBox.setItems("Active", "Inactive");
         return statusComboBox;
-        }).setHeader("Change Status");
-        grid.addComponentColumn((ValueProvider<Employee, Component>) employee -> {
-            final Button edit = new Button("Edit");
-            edit.addClickListener((ComponentEventListener<ClickEvent<Button>>) buttonClickEvent -> {
-                // no-op
-            });
-            return edit;
-        });
-        grid.addComponentColumn((ValueProvider<Employee, Component>) employee -> {
-            final Button save = new Button("Save");
-            save.addClickListener((ComponentEventListener<ClickEvent<Button>>) buttonClickEvent -> {
-                // no-op
-            });
-            return save;
-        });
-        this.previous = new Button("Previous");
-        this.previous.addClickListener((ComponentEventListener<ClickEvent<Button>>) buttonClickEvent -> {
-            if (currentPage > 1) {
+    }
+
+    private Button createEditButton() {
+        return new Button("Edit");
+    }
+    private Button createSaveButton() {
+        return new Button("Save");
+    }
+
+    private void addNavigationButtons() {
+        final HorizontalLayout hf = new HorizontalLayout();
+        previous = createNavigationButton("Previous", -1);
+        next = createNavigationButton("Next", 1);
+        hf.add(previous, next, createAddEmployeeButton());
+        add(hf);
+    }
+
+    private Button createNavigationButton(String label, int increment) {
+        Button button = new Button(label);
+        button.addClickListener(event -> changePage(increment));
+        return button;
+    }
+    private void changePage(int increment) {
+        if (increment < 0 && currentPage > 1) {
             currentPage--;
-                updateGrid(grid);
-            }
-        });
-        hf.add(this.previous);
-        this.next = new Button("Next");
-        this.next.addClickListener((ComponentEventListener<ClickEvent<Button>>) buttonClickEvent -> {
-            if (employeeService.hasNextPage(currentPage, pageSize)) {
+        } else if (increment > 0 && employeeService.hasNextPage(currentPage, pageSize, sortField, ascending)) {
             currentPage++;
-                updateGrid(grid);
         }
-        });
-        hf.add(this.next);
-        final Button addEmployee = new Button("Add Employee");
-        addEmployee.addClickListener((ComponentEventListener<ClickEvent<Button>>) buttonClickEvent -> {
-            this.getUI().flatMap(ui -> ui.navigate(EmployeeView.class, "new"));
-        });
-        hf.add(addEmployee);
-        add(title, hl, grid, hf);
-        updateGrid(grid);
+        updateGrid();
     }
-    private void updateGrid(VGrid<Employee> grid) {
-        Page<Employee> page = employeeService.getEmployeesPaginated(currentPage, pageSize);
+    private Button createAddEmployeeButton() {
+        return new Button("Add Employee", event ->
+                getUI().flatMap(ui -> ui.navigate(EmployeeView.class, "new"))
+        );
+    }
+    private void updateGrid() {
+        Page<Employee> page = employeeService.getEmployeesPaginated(currentPage, pageSize, sortField, ascending);
         grid.setItems(page.getContent());
-        this.previous.setEnabled(currentPage > 1);
-        this.next.setEnabled(page.hasNext());
+        previous.setEnabled(currentPage > 1);
+        next.setEnabled(page.hasNext());
     }
 }