[BAEL-6105] code for list to page article

persistence-modules/spring-data-jpa-query-3/pom.xml

@@ -30,6 +30,11 @@
             <artifactId>javafaker</artifactId>
             <version>${javafaker.version}</version>
         </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-web</artifactId>
+        </dependency>
+
         <dependency>
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-starter-test</artifactId>

persistence-modules/spring-data-jpa-query-3/src/main/java/com/baeldung/spring/data/jpa/paging/Customer.java

@@ -0,0 +1,14 @@
+package com.baeldung.spring.data.jpa.paging;
+
+public class Customer {
+
+   private String name;
+
+    public Customer(String name) {
+        this.name = name;
+    }
+
+    public String getName() {
+        return name;
+    }
+}

persistence-modules/spring-data-jpa-query-3/src/main/java/com/baeldung/spring/data/jpa/paging/CustomerRepository.java

@@ -0,0 +1,9 @@
+package com.baeldung.spring.data.jpa.paging;
+
+import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.stereotype.Repository;
+
+@Repository
+public interface CustomerRepository extends JpaRepository<Customer, Long> {
+
+}

persistence-modules/spring-data-jpa-query-3/src/main/java/com/baeldung/spring/data/jpa/paging/CustomerRestController.java

@@ -0,0 +1,31 @@
+package com.baeldung.spring.data.jpa.paging;
+
+import org.springframework.data.domain.Page;
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RequestParam;
+import org.springframework.web.bind.annotation.RestController;
+
+@RestController
+public class CustomerRestController {
+
+    private final CustomerService customerService;
+
+    public CustomerRestController(CustomerService customerService) {
+        this.customerService = customerService;
+    }
+
+    @GetMapping("/api/customers")
+    public ResponseEntity<Page<Customer>> getCustomers(@RequestParam(defaultValue = "0") int page, @RequestParam(defaultValue = "10") int size) {
+
+        Page<Customer> customerPage = customerService.getCustomers(page, size);
+        HttpHeaders headers = new HttpHeaders();
+        headers.add("X-Page-Number", String.valueOf(customerPage.getNumber()));
+        headers.add("X-Page-Size", String.valueOf(customerPage.getSize()));
+
+        return ResponseEntity.ok()
+          .headers(headers)
+          .body(customerPage);
+    }
+}

persistence-modules/spring-data-jpa-query-3/src/main/java/com/baeldung/spring/data/jpa/paging/CustomerService.java

@@ -0,0 +1,37 @@
+package com.baeldung.spring.data.jpa.paging;
+
+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;
+
+@Service
+public class CustomerService {
+
+    public CustomerService(CustomerRepository customerRepository) {
+        this.customerRepository = customerRepository;
+    }
+
+     private final CustomerRepository customerRepository;
+
+    public Page<Customer> getCustomers(int page, int size) {
+
+        Pageable pageRequest = createPageRequestUsing(page, size);
+
+        List<Customer> allCustomers = customerRepository.findAll();
+        int start = (int) pageRequest.getOffset();
+        int end = Math.min((start + pageRequest.getPageSize()), allCustomers.size());
+
+
+        return new PageImpl<>(allCustomers.subList(start, end), pageRequest, allCustomers.size());
+
+    }
+
+    private Pageable createPageRequestUsing(int page, int size) {
+        return PageRequest.of(page, size);
+
+    }
+}

persistence-modules/spring-data-jpa-query-3/src/main/java/com/baeldung/spring/data/jpa/paging/PagingApplication.java

@@ -0,0 +1,12 @@
+package com.baeldung.spring.data.jpa.paging;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class PagingApplication {
+
+    public static void main(String[] args) {
+        SpringApplication.run(PagingApplication.class, args);
+    }
+}

persistence-modules/spring-data-jpa-query-3/src/test/java/com/baeldung/spring/data/jpa/paging/CustomerControllerTest.java

@@ -0,0 +1,76 @@
+package com.baeldung.spring.data.jpa.paging;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.when;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.stream.IntStream;
+
+import org.assertj.core.api.Assertions;
+import org.json.JSONObject;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
+import org.springframework.boot.test.mock.mockito.MockBean;
+import org.springframework.data.domain.Page;
+import org.springframework.data.domain.PageImpl;
+import org.springframework.data.domain.PageRequest;
+import org.springframework.mock.web.MockHttpServletResponse;
+import org.springframework.test.web.servlet.MockMvc;
+import org.springframework.test.web.servlet.MvcResult;
+
+
+@WebMvcTest(CustomerRestController.class)
+public class CustomerControllerTest {
+
+    @Autowired
+    private MockMvc mockMvc;
+
+    @MockBean
+    private CustomerService customerService;
+
+    @BeforeEach
+    void setup() {
+        List<Customer> allCustomers = getAllCustomers();
+        Page<Customer> customerPage = new PageImpl<>(allCustomers, PageRequest.of(1, 5), allCustomers.size());
+
+        when(customerService.getCustomers(1, 5)).thenReturn(customerPage);
+
+    }
+
+    private static List<Customer> getAllCustomers() {
+        List<Customer> customers = new ArrayList<>();
+        IntStream.range(0, 20)
+          .forEach(i -> {
+              Customer customer = new Customer((Integer.toString(i)));
+              customers.add(customer);
+          });
+        return customers;
+    }
+
+    @Test
+    void givenTotalCustomers20_whenGetRequestWithPageAndSize_thenPagedReponseIsReturnedFromDesiredPageAndSize() throws Exception {
+
+        MvcResult result = mockMvc.perform(get("/api/customers?page=1&size=5"))
+          .andExpect(status().isOk())
+          .andReturn();
+
+        MockHttpServletResponse response = result.getResponse();
+
+        JSONObject jsonObject = new JSONObject(response.getContentAsString());
+        assertThat(jsonObject.get("totalPages"))
+          .isEqualTo(4);
+        assertThat(jsonObject.get("totalElements"))
+          .isEqualTo(20);
+        assertThat(jsonObject.get("number"))
+          .isEqualTo(1);
+        assertThat(jsonObject.get("size"))
+          .isEqualTo(5);
+        assertThat(jsonObject.get("content"))
+          .isNotNull();
+    }
+}

persistence-modules/spring-data-jpa-query-3/src/test/java/com/baeldung/spring/data/jpa/paging/CustomerServiceTest.java

@@ -0,0 +1,80 @@
+package com.baeldung.spring.data.jpa.paging;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.mockito.Mockito.when;
+
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.MethodSource;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+import org.springframework.data.domain.Page;
+
+@ExtendWith(MockitoExtension.class)
+public class CustomerServiceTest {
+
+    @Mock
+    private CustomerRepository customerRepository;
+
+    @InjectMocks
+    private CustomerService customerService;
+
+    private static final List<Customer> ALL_CUSTOMERS = Arrays.asList(
+      new Customer("Ali"), new Customer("Brian"), new Customer("Coddy"),
+      new Customer("Di"), new Customer("Eve"), new Customer("Fin"),
+      new Customer("Grace"), new Customer("Harry"),
+      new Customer("Ivan"), new Customer("Judy"),
+      new Customer("Kasim"), new Customer("Liam"),
+      new Customer("Mike"),new Customer("Nick"),
+      new Customer("Omar"), new Customer("Penny"),
+      new Customer("Queen"),new Customer("Rob"),
+      new Customer("Sue"),new Customer("Tammy"));
+
+    private static final List<String> PAGE_1_CONTENTS = Arrays.asList("Ali", "Brian", "Coddy", "Di", "Eve");
+
+    private static final List<String> PAGE_2_CONTENTS = Arrays.asList("Fin", "Grace", "Harry", "Ivan", "Judy");
+
+    private static final List<String> PAGE_3_CONTENTS = Arrays.asList("Kasim", "Liam", "Mike", "Nick", "Omar");
+
+    private static final List<String> PAGE_4_CONTENTS = Arrays.asList("Penny", "Queen", "Rob", "Sue", "Tammy");
+
+    private static final List<String> EMPTY_PAGE = Arrays.asList();
+    @BeforeEach
+    void setup() {
+        when(customerRepository.findAll()).thenReturn(ALL_CUSTOMERS);
+    }
+
+    private static Collection<Object[]> testIO() {
+        return Arrays.asList(
+          new Object[][] {
+          { 0, 5, PAGE_1_CONTENTS, 20L, 4L },
+          { 1, 5, PAGE_2_CONTENTS, 20L, 4L },
+          { 2, 5, PAGE_3_CONTENTS, 20L, 4L },
+          { 3, 5, PAGE_4_CONTENTS, 20L, 4L },
+          { 4, 5, EMPTY_PAGE, 20L, 4L } }
+        );
+    }
+
+    @ParameterizedTest
+    @MethodSource("testIO")
+    void givenAListOfCustomers_whenGetCustomers_thenReturnsDesiredDataAlongWithPagingInformation(int page, int size, List<String> expectedNames, long expectedTotalElements, long expectedTotalPages) {
+        Page<Customer> customers = customerService.getCustomers(page, size);
+        List<String> names = customers.getContent()
+          .stream()
+          .map(Customer::getName)
+          .collect(Collectors.toList());
+
+        assertEquals(expectedNames.size(), names.size());
+        assertEquals(expectedNames, names);
+        assertEquals(expectedTotalElements, customers.getTotalElements());
+        assertEquals(expectedTotalPages, customers.getTotalPages());
+    }
+}