Spring Data JPA Specification With Pagination

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The combination of Specification and Pageable in Spring Data JPA makes it super easy to fetch data with dynamic conditions and pagination. Let's walk through a step-by-step example using a Student entity.

1. Setting up the Project

Make sure you have the necessary dependencies in your pom.xml:

<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-jpa</artifactId> </dependency> 

2. Define the Entity

@Entity public class Student { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id; private String name; private String course; private Double grade; // getters, setters, etc. } 

3. Create the Repository:

Extend both JpaRepository and JpaSpecificationExecutor:

public interface StudentRepository extends JpaRepository<Student, Long>, JpaSpecificationExecutor<Student> { } 

4. Define Specifications

public class StudentSpecifications { public static Specification<Student> hasName(String name) { return (root, query, criteriaBuilder) -> criteriaBuilder.like(root.get("name"), "%" + name + "%"); } public static Specification<Student> inCourse(String course) { return (root, query, criteriaBuilder) -> criteriaBuilder.equal(root.get("course"), course); } public static Specification<Student> hasGradeAbove(Double grade) { return (root, query, criteriaBuilder) -> criteriaBuilder.greaterThan(root.get("grade"), grade); } } 

5. Create a Service to Query with Pagination

@Service public class StudentService { @Autowired private StudentRepository studentRepository; public Page<Student> findStudents(String name, String course, Double grade, Pageable pageable) { return studentRepository.findAll( Specification.where(StudentSpecifications.hasName(name)) .and(StudentSpecifications.inCourse(course)) .and(StudentSpecifications.hasGradeAbove(grade)), pageable ); } } 

6. Using the Service:

You can use the PageRequest class to create an instance of Pageable:

@Autowired private StudentService studentService; public void fetchStudents() { Pageable firstPageWithTwoElements = PageRequest.of(0, 2); Page<Student> students = studentService.findStudents("John", "Mathematics", 80.0, firstPageWithTwoElements); // Access the list of students using students.getContent() for (Student student : students.getContent()) { // process each student } } 

7. Extending to Controllers

If you are integrating this into a web application, it's typical to pass pagination parameters like page, size, and sort from the client side:

@RestController @RequestMapping("/students") public class StudentController { @Autowired private StudentService studentService; @GetMapping public ResponseEntity<Page<Student>> getStudents( @RequestParam(required = false) String name, @RequestParam(required = false) String course, @RequestParam(required = false) Double grade, @RequestParam(defaultValue = "0") int page, @RequestParam(defaultValue = "10") int size, @RequestParam(defaultValue = "id,asc") String[] sort) { List<Sort.Order> orders = new ArrayList<>(); for (String sortOrder : sort) { String[] _sort = sortOrder.split(","); orders.add(new Sort.Order(_sort[1].equalsIgnoreCase("desc") ? Sort.Direction.DESC : Sort.Direction.ASC, _sort[0])); } Page<Student> students = studentService.findStudents(name, course, grade, PageRequest.of(page, size, Sort.by(orders))); return new ResponseEntity<>(students, HttpStatus.OK); } } 

That's it! With this setup, you can create dynamic queries based on filters (like name, course, and grade) and fetch results with pagination and sorting.