通過在彈簧資料 JPA 中使用自定義查詢傳遞 parmeter 來進行分頁

我使用 Spring Boot 1.4.4.RELEASE，使用 MySQL 作為資料庫和 Spring Data JPA 抽象來與 MySQL 一起工作。實際上，Spring Data JPA 模組使得在 Spring 引導應用程式中首先設定 Pagination 變得如此簡單。

場景暴露端點/學生/教室/ {id}。它將根據頁面和大小引數以及隨之傳遞的 classroomId 返回學生列表和其他分頁資訊（我們將在一分鐘內看到）。

首先，我建立一個域學生

@Entity
@Table(name = "student")
public class Student {  

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(name = "name")
    private String name;

    @NotNull
    @Column(name = "rollnumber", nullable = false)
    private Integer rollnumber;

    @Column(name = "date_of_birth")
    private LocalDate dateOfBirth;

    @Column(name = "address")
    private String address;

    @ManyToOne(optional = false)
    @NotNull
    private Classroom classroom;

//getter and setter

}

學生與課堂有關

@Entity
@Table(name = "classroom")
public class Classroom  {  

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(name = "standard")
    private String standard;

    @Column(name = "section")
    private String section;

    @Column(name = "year")
    private String year;

//getter && setter

}

我們有 RestController

@RestController
@RequestMapping("/api")
public class StudentResource {

private final StudentService studentService;

    public StudentResource(StudentService studentService) {
        this.studentService = studentService;
    }

 @GetMapping("/students/classroom/{id}")
    public ResponseEntity<Page<StudentDTO>> getAllStudentsBasedOnClassroom(@ApiParam Pageable pageable,@PathVariable Long id)
        throws URISyntaxException {           
        Page<StudentDTO> page = studentService.findByClassroomId(id, pageable);
        HttpHeaders headers = PaginationUtil.generatePaginationHttpHeaders(page, "/api/students/classroom");
        return new ResponseEntity<Page<StudentDTO>>(page, headers, HttpStatus.OK);
    }

}

請注意，我們還沒有將 RequestParams 傳遞給我們的處理程式方法。當命中端點/ students / classroom / 1？page = 0＆size = 3 時，Spring 會自動解析頁面和大小引數並建立一個 Pageable 例項。然後我們將這個 Pageable 例項傳遞給 Service 層，它將它傳遞給我們的 Repository 層。

服務類

public interface StudentService {

  Page<StudentDTO> findByClassroomId(Long id,Pageable pageable);

}

service impl（這裡我是使用者 StudentMapper，使用 mapStruct 將 Class 轉換為 DTOby，或者我們可以手工製作）

@Service
@Transactional
public class StudentServiceImpl implements StudentService{

 private final StudentRepository studentRepository;

    private final StudentMapper studentMapper;

    public StudentServiceImpl(StudentRepository studentRepository, StudentMapper studentMapper) {
        this.studentRepository = studentRepository;
        this.studentMapper = studentMapper;
    }
@Override
    public Page<StudentDTO> findByClassroomId(Long id, Pageable pageable) {
         log.debug("Request to get Students based on classroom : {}", id);
         Page<Student> result = studentRepository.findByClassroomId(id, pageable);
         return result.map(student -> studentMapper.studentToStudentDTO(student));
    }

}

這是對映器介面

@Mapper(componentModel = "spring", uses = {})
public interface StudentMapper{

  StudentDTO   studentToStudentDTO(Student student);
}

然後在 StudentRepository 我 worte 自定義方法

public interface StudentRepository extends JpaRepository<Student,Long> {

    Page<Student> findByClassroomId(Long id, Pageable pageable);    
    
}

然後它會給我們所有以下資訊和相應的資料

"last": false,
  "totalElements": 20,
  "totalPages": 7,
  "size": 3,
  "number": 0,
  "sort": null,
  "first": true,
  "numberOfElements": 3