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Spring Boot
Spring Boot JPA Specifications (Specification<T>)

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Spring Data JPA Specifications allow you to create dynamic queries with filtering conditions in a flexible way.

Why Use Specification<T>?

  • Build dynamic queries based on user input.
  • Avoid writing multiple static queries.
  • Combine multiple conditions easily (AND, OR).
  • Supports pagination & sorting.

Adding Dependency

Ensure you have Spring Data JPA dependency and lombok in your pom.xml:

<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.34</version>
<scope>provided</scope>
</dependency>

Example Entity Class

Let's assume we have a User entity with fields: id, name, email and age

user.java
import jakarta.persistence.*;
import lombok.*;

@Entity
@Table(name = "user")
@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
public class User {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;

private String name;
private String email;
private int age;
}

Table name : user

id name email age
1 John john@gmail.com 25
2 Mike mike@gmail.com 35
3 Watson watson@gmail.com 40
4 Kenny kenny@gmail.com 45

Create Specification

UserService.java
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.jpa.domain.Specification;
import org.springframework.stereotype.Service;
import java.util.List;

@Service
public class UserService {
@Autowired
private UserRepository userRepository;

// ✅ Get Users with Dynamic Filters
public List<User> searchUsers(String name, Integer age, String email) {
Specification<User> spec = Specification.where(UserSpecification.hasName(name))
.or(UserSpecification.hasAgeGreaterThan(age))
.or(UserSpecification.hasEmail(email));
return userRepository.findAll(spec);
}
}

Each method returns a Specification<User> that dynamically applies a filtering condition.

Create Repository Using JpaSpecificationExecutor

  • Spring Data JPA provides JpaSpecificationExecutor for dynamic queries.
  • JpaSpecificationExecutor<User> allows dynamic querying with Specification<User>.
UserRepository.java
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;

public interface UserRepository extends JpaRepository<User, Long>, JpaSpecificationExecutor<User> {
}

Create Services

UserService.java
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.jpa.domain.Specification;
import org.springframework.stereotype.Service;
import java.util.List;

@Service
public class UserService {
@Autowired
private UserRepository userRepository;

// ✅ Get Users with Dynamic Filters
public List<User> searchUsers(String name, Integer age, String email) {
Specification<User> spec = Specification.where(UserSpecification.hasName(name))
.or(UserSpecification.hasAgeGreaterThan(age))
.or(UserSpecification.hasEmail(email));
return userRepository.findAll(spec);
}
}

Create Controllers

UserController.java
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;
import java.util.List;

@RestController
@RequestMapping("/users")
public class UserController {
@Autowired
private UserService userService;

// ✅ Search Users with Filters
@GetMapping("/search")
public ResponseEntity<List<User>> searchUsers(
@RequestParam(required = false) String name,
@RequestParam(required = false) Integer age,
@RequestParam(required = false) String email) {

return ResponseEntity.ok(userService.searchUsers(name, age, email));
}
}

Testing the REST API with Postman:

Once the application is running, test the endpoints:


Get User like name GET:http://localhost:8080/users/search?name=John

SELECT * FROM users WHERE name LIKE '%John%';

Get User by age greaterThanOrEqualTo GET:http://localhost:8080/users/search?age=40

SELECT * FROM users WHERE age >= 25;

Get User by like name or greaterThanOrEqualTo age GET:http://localhost:8080/users/search?name=John&age=40

SELECT * FROM users WHERE name LIKE '%John%' OR age >= 25;

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