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When building a contact form backend in Spring Boot, it's good practice to separate your internal entity from incoming API requests. This can be done using a DTO (Data Transfer Object) — in our case, a ContactRequest. In this post, we’ll walk through creating a JPA-backed contact service that uses a ContactRequest DTO for request handling.

📩 Step 1: Define the ContactRequest DTO

The DTO serves as the structure for incoming request payloads.

java

public class ContactRequest {
    private String name;
    private String email;
    private String subject;
    private String message;

    // Getters and Setters
}

📦 Step 2: Define the Contact Entity

This entity will be stored in the database.

java

import javax.persistence.*;

@Entity
public class Contact {

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

    private String name;
    private String email;
    private String subject;
    private String message;

    // Getters and Setters
}

💾 Step 3: Create a JPA Repository

java

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

@Repository
public interface ContactRepository extends JpaRepository<Contact, Long> {
}

⚙️ Step 4: Define the Service Interface

Update the service interface to accept the ContactRequest DTO for create and update operations.

java

import java.util.List;

public interface ContactService {
    Contact saveContact(ContactRequest contactRequest);
    List<Contact> getAllContacts();
    Contact getContactById(Long id);
    Contact updateContact(Long id, ContactRequest contactRequest);
    void deleteContact(Long id);
}

🧠 Step 5: Implement the Service Logic

Here’s the full implementation that maps between the DTO and entity:

java

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class ContactServiceImpl implements ContactService {

    @Autowired
    private ContactRepository contactRepository;

    @Override
    public Contact saveContact(ContactRequest contactRequest) {
        Contact contact = new Contact();
        contact.setName(contactRequest.getName());
        contact.setEmail(contactRequest.getEmail());
        contact.setSubject(contactRequest.getSubject());
        contact.setMessage(contactRequest.getMessage());
        return contactRepository.save(contact);
    }

    @Override
    public List<Contact> getAllContacts() {
        return contactRepository.findAll();
    }

    @Override
    public Contact getContactById(Long id) {
        return contactRepository.findById(id)
                .orElseThrow(() -> new ResourceNotFoundException("Contact not found with id: " + id));
    }

    @Override
    public Contact updateContact(Long id, ContactRequest contactRequest) {
        Contact contact = getContactById(id);
        contact.setName(contactRequest.getName());
        contact.setEmail(contactRequest.getEmail());
        contact.setSubject(contactRequest.getSubject());
        contact.setMessage(contactRequest.getMessage());
        return contactRepository.save(contact);
    }

    @Override
    public void deleteContact(Long id) {
        Contact contact = getContactById(id);
        contactRepository.delete(contact);
    }
}

🌐 Step 6: Add a REST Controller

This is how your controller can use the ContactRequest for handling HTTP requests.

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("/api/contacts")
public class ContactController {

    @Autowired
    private ContactService contactService;

    @PostMapping
    public ResponseEntity<Contact> createContact(@RequestBody ContactRequest contactRequest) {
        return ResponseEntity.ok(contactService.saveContact(contactRequest));
    }

    @GetMapping
    public ResponseEntity<List<Contact>> getAllContacts() {
        return ResponseEntity.ok(contactService.getAllContacts());
    }

    @GetMapping("/{id}")
    public ResponseEntity<Contact> getContactById(@PathVariable Long id) {
        return ResponseEntity.ok(contactService.getContactById(id));
    }

    @PutMapping("/{id}")
    public ResponseEntity<Contact> updateContact(@PathVariable Long id, @RequestBody ContactRequest contactRequest) {
        return ResponseEntity.ok(contactService.updateContact(id, contactRequest));
    }

    @DeleteMapping("/{id}")
    public ResponseEntity<Void> deleteContact(@PathVariable Long id) {
        contactService.deleteContact(id);
        return ResponseEntity.noContent().build();
    }
}

🚨 Step 7: Add Exception Handling (Optional but Recommended)

java

import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.ResponseStatus;

@ResponseStatus(HttpStatus.NOT_FOUND)
public class ResourceNotFoundException extends RuntimeException {
    public ResourceNotFoundException(String message) {
        super(message);
    }
}

✅ Summary

By introducing a ContactRequest DTO, you've added an abstraction layer between your REST API and your database, making your code more flexible and easier to maintain. This clean approach enables:

• Separation of concerns
• Future-proofing against changes in internal data structures
• Better validation and transformation support