[BAEL-6318] code for consuming Page<Entity> using rest template

persistence-modules/spring-data-rest-2/src/main/java/com/baeldung/pageentityresponse/CustomPageImpl.java

@@ -0,0 +1,36 @@
+package com.baeldung.pageentityresponse;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.springframework.data.domain.PageImpl;
+import org.springframework.data.domain.PageRequest;
+import org.springframework.data.domain.Pageable;
+
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.databind.JsonNode;
+
+@JsonIgnoreProperties(ignoreUnknown = true)
+public class CustomPageImpl<T> extends PageImpl<T> {
+
+    @JsonCreator(mode = JsonCreator.Mode.PROPERTIES)
+    public CustomPageImpl(@JsonProperty("content") List<T> content, @JsonProperty("number") int number, @JsonProperty("size") int size, @JsonProperty("totalElements") Long totalElements, @JsonProperty("pageable") JsonNode pageable,
+      @JsonProperty("last") boolean last, @JsonProperty("totalPages") int totalPages, @JsonProperty("sort") JsonNode sort, @JsonProperty("numberOfElements") int numberOfElements) {
+        super(content, PageRequest.of(number, 1), 10);
+
+    }
+
+    public CustomPageImpl(List<T> content, Pageable pageable, long total) {
+        super(content, pageable, total);
+    }
+
+    public CustomPageImpl(List<T> content) {
+        super(content);
+    }
+
+    public CustomPageImpl() {
+        super(new ArrayList<>());
+    }
+}

persistence-modules/spring-data-rest-2/src/main/java/com/baeldung/pageentityresponse/EmployeeClient.java

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+package com.baeldung.pageentityresponse;
+
+import org.springframework.core.ParameterizedTypeReference;
+import org.springframework.data.domain.Page;
+import org.springframework.data.domain.Pageable;
+import org.springframework.http.HttpMethod;
+import org.springframework.http.ResponseEntity;
+import org.springframework.stereotype.Component;
+import org.springframework.web.client.RestTemplate;
+import org.springframework.web.util.UriComponentsBuilder;
+
+@Component
+public class EmployeeClient {
+    private final RestTemplate restTemplate;
+
+    public EmployeeClient(RestTemplate restTemplate) {
+        this.restTemplate = restTemplate;
+    }
+
+    public Page<EmployeeDto> getEmployeeDataFromExternalAPI(Pageable pageable) {
+        String url = "http://localhost:8080/external-service/employee";
+
+        UriComponentsBuilder uriBuilder = UriComponentsBuilder.fromUriString(url)
+          .queryParam("page", pageable.getPageNumber())
+          .queryParam("size", pageable.getPageSize());
+
+        ResponseEntity<CustomPageImpl<EmployeeDto>> responseEntity = restTemplate.exchange(uriBuilder.toUriString(), HttpMethod.GET, null, new ParameterizedTypeReference<CustomPageImpl<EmployeeDto>>() {
+        });
+
+        return responseEntity.getBody();
+    }
+}

persistence-modules/spring-data-rest-2/src/main/java/com/baeldung/pageentityresponse/EmployeeController.java

@@ -0,0 +1,56 @@
+package com.baeldung.pageentityresponse;
+
+import java.util.ArrayList;
+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.http.ResponseEntity;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RequestParam;
+import org.springframework.web.bind.annotation.RestController;
+
+@RestController
+@RequestMapping("/organisation")
+public class EmployeeController {
+
+    private final EmployeeService organisationService;
+
+    public EmployeeController(EmployeeService organisationService) {
+        this.organisationService = organisationService;
+    }
+
+    @GetMapping("/employee")
+    public ResponseEntity<Page<EmployeeDto>> getEmployeeData(Pageable pageable) {
+        Page<EmployeeDto> employeeData = organisationService.getEmployeeData(pageable);
+        return ResponseEntity.ok(employeeData);
+    }
+
+    @GetMapping("/data")
+    public ResponseEntity<Page<EmployeeDto>> getData(@RequestParam(defaultValue = "0") int page, @RequestParam(defaultValue = "10") int size) {
+        List<EmployeeDto> empList = listImplementation();
+
+        int totalSize = empList.size();
+        int startIndex = page * size;
+        int endIndex = Math.min(startIndex + size, totalSize);
+
+        List<EmployeeDto> pageContent = empList.subList(startIndex, endIndex);
+
+        Page<EmployeeDto> employeeDtos = new PageImpl<>(pageContent, PageRequest.of(page, size), totalSize);
+
+        return ResponseEntity.ok()
+          .body(employeeDtos);
+    }
+
+    private static List<EmployeeDto> listImplementation() {
+        List<EmployeeDto> empList = new ArrayList<>();
+        empList.add(new EmployeeDto("Jane", "Finance", 50000));
+        empList.add(new EmployeeDto("Sarah", "IT", 70000));
+        empList.add(new EmployeeDto("John", "IT", 90000));
+        return empList;
+    }
+
+}

persistence-modules/spring-data-rest-2/src/main/java/com/baeldung/pageentityresponse/EmployeeDto.java

@@ -0,0 +1,48 @@
+package com.baeldung.pageentityresponse;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+
+public class EmployeeDto {
+    @JsonProperty("name")
+    private String name;
+
+    @JsonProperty("dept")
+    private String dept;
+
+    @JsonProperty("salary")
+    private long salary;
+
+    public EmployeeDto() {
+    }
+
+    public EmployeeDto(String name, String dept, long salary) {
+        this.name = name;
+        this.dept = dept;
+        this.salary = salary;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public String getDept() {
+        return dept;
+    }
+
+    public void setDept(String dept) {
+        this.dept = dept;
+    }
+
+    public long getSalary() {
+        return salary;
+    }
+
+    public void setSalary(long salary) {
+        this.salary = salary;
+    }
+}
+

persistence-modules/spring-data-rest-2/src/main/java/com/baeldung/pageentityresponse/EmployeeService.java

@@ -0,0 +1,18 @@
+package com.baeldung.pageentityresponse;
+
+import org.springframework.data.domain.Page;
+import org.springframework.data.domain.Pageable;
+import org.springframework.stereotype.Service;
+
+@Service
+public class EmployeeService {
+    private final EmployeeClient employeeClient;
+
+    public EmployeeService(EmployeeClient employeeClient) {
+        this.employeeClient = employeeClient;
+    }
+
+    public Page<EmployeeDto> getEmployeeData(Pageable pageable) {
+        return employeeClient.getEmployeeDataFromExternalAPI(pageable);
+    }
+}

persistence-modules/spring-data-rest-2/src/main/java/com/baeldung/pageentityresponse/PageEntityResponseApp.java

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

persistence-modules/spring-data-rest-2/src/main/java/com/baeldung/pageentityresponse/RestTemplateConfig.java

@@ -0,0 +1,15 @@
+package com.baeldung.pageentityresponse;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.web.client.RestTemplate;
+
+@Configuration
+public class RestTemplateConfig {
+
+    @Bean
+    public RestTemplate restTemplate() {
+        return new RestTemplate();
+    }
+}
+

persistence-modules/spring-data-rest-2/src/test/java/com/baeldung/pageentityresponse/EmployeeClientUnitTest.java

@@ -0,0 +1,65 @@
+package com.baeldung.pageentityresponse;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.mockito.Mockito.eq;
+import static org.mockito.Mockito.isNull;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+
+import java.util.Arrays;
+import org.junit.jupiter.api.Test;
+import org.mockito.Mockito;
+import org.springframework.core.ParameterizedTypeReference;
+import org.springframework.data.domain.Page;
+import org.springframework.data.domain.PageRequest;
+import org.springframework.http.HttpMethod;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.client.RestTemplate;
+
+public class EmployeeClientUnitTest {
+
+  @Test
+  void givenRestTemplate_whenGetEmployeeDataFromExternalAPI_thenGetPageDataWithContents() {
+    CustomPageImpl<EmployeeDto> mockedResponse = new CustomPageImpl<>(Arrays.asList(
+        new EmployeeDto("Jane", "Finance", 50000),
+        new EmployeeDto("Sarah", "IT", 70000),
+        new EmployeeDto("John", "IT", 90000)
+    ));
+
+    RestTemplate restTemplate = mock(RestTemplate.class);
+    ResponseEntity<CustomPageImpl<EmployeeDto>> responseEntity = new ResponseEntity<>(mockedResponse,
+        HttpStatus.OK);
+
+    String url = "http://localhost:8080/employee";
+    int pageNumber = 0;
+    int pageSize = 10;
+    String expectedUrl = url + "?page=" + pageNumber + "&size=" + pageSize;
+
+    HttpMethod expectedMethod = HttpMethod.GET;
+    ParameterizedTypeReference<CustomPageImpl<EmployeeDto>> responseType =  new ParameterizedTypeReference<CustomPageImpl<EmployeeDto>>() {
+    };
+
+    Mockito.when(restTemplate.exchange(
+        expectedUrl,
+        expectedMethod,
+        null,
+        responseType
+    )).thenReturn(responseEntity);
+
+    EmployeeClient employeeClient = new EmployeeClient(restTemplate);
+
+    Page<EmployeeDto> result = employeeClient.getEmployeeDataFromExternalAPI(
+        PageRequest.of(pageNumber, pageSize)
+    );
+
+    verify(restTemplate).exchange(
+        eq(expectedUrl),
+        eq(expectedMethod),
+        isNull(),
+        eq(responseType)
+    );
+    assertEquals(1, result.getNumberOfElements());
+    assertEquals(mockedResponse, result.getContent().get(0));
+  }
+}

persistence-modules/spring-data-rest-2/src/test/java/com/baeldung/pageentityresponse/EmployeeControllerIntegrationTest.java

@@ -0,0 +1,64 @@
+package com.baeldung.pageentityresponse;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import java.util.List;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.boot.test.web.client.TestRestTemplate;
+import org.springframework.boot.web.server.LocalServerPort;
+import org.springframework.core.ParameterizedTypeReference;
+import org.springframework.data.domain.PageImpl;
+import org.springframework.http.HttpMethod;
+import org.springframework.http.ResponseEntity;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+@SpringBootTest(classes = PageEntityResponseApp.class,  webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
+@AutoConfigureMockMvc
+public class EmployeeControllerIntegrationTest {
+
+  @LocalServerPort
+  private int port;
+
+  @Autowired
+  private TestRestTemplate restTemplate;
+
+@Test
+void givenGetData_whenRestTemplateExchange_thenReturnsPageOfEmployee() {
+  ResponseEntity<CustomPageImpl<EmployeeDto>> responseEntity = restTemplate.exchange(
+      "http://localhost:" + port + "/organisation/data",
+      HttpMethod.GET,
+      null,
+      new ParameterizedTypeReference<CustomPageImpl<EmployeeDto>>() {}
+  );
+
+  assertEquals(200, responseEntity.getStatusCodeValue());
+  PageImpl<EmployeeDto> restPage = responseEntity.getBody();
+  assertNotNull(restPage);
+
+  assertEquals(10, restPage.getTotalElements());
+
+  List<EmployeeDto> content = restPage.getContent();
+  assertNotNull(content);
+  assertEquals(3, content.size());
+
+  EmployeeDto employee1 = content.get(0);
+  assertEquals("Jane", employee1.getName());
+  assertEquals("Finance", employee1.getDept());
+  assertEquals(50000, employee1.getSalary());
+
+  EmployeeDto employee2 = content.get(1);
+  assertEquals("Sarah", employee2.getName());
+  assertEquals("IT", employee2.getDept());
+  assertEquals(70000, employee2.getSalary());
+
+  EmployeeDto employee3 = content.get(2);
+  assertEquals("John", employee3.getName());
+  assertEquals("IT", employee3.getDept());
+  assertEquals(90000, employee3.getSalary());
+}
+
+}