Spring Boot - Multithreading on same Object - multithreading

Question

I work on project that manages contacts database with CRUD options
But I don't know how to handle multithreading.
I use Java 8 and spring-boot 2.0.4 RELEASE
UPDATE -> Code instead of images
This is Controller :
#RestController
#RequestMapping("/api")
#CrossOrigin(origins = "http://localhost:4200", allowedHeaders="*")
public class ContactController {
#Autowired
private ContactService contactService;
/*--- Toute la liste ---*/
#GetMapping("/contact")
public List<ContactDTO> getDestinataires() {
return contactService.getContacts();
}
/* ------------------------- CRUD ----------------------- */
// Creation contact
#PostMapping("/contact/create")
public boolean create(#Valid #RequestBody ContactDTO contact) {
return contactService.create(contact);
}
// infos d'un contact
#GetMapping("/contact/{id}")
public ContactDTO read(#PathVariable Integer id) {
return contactService.getContact(id);
}
// Maj contact
#PutMapping("/contact/update")
public boolean update(#RequestBody ContactDTO contact) {
return contactService.update(contact);
}
// Maj contact
#DeleteMapping("/contact/delete/{id}")
public boolean delete(#PathVariable Integer id) {
return contactService.delete(id);
}
}
The service (with #Service annotation) retrieves ContactDTO Object sent by the front and set Contact object. It works with CoreServices (without Spring annotations) java class.
This is it:
#Service
public class ContactService extends CoreServices{
private static final org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(ContactService.class);
public boolean update(ContactDTO contactDTOFront) {
logger.info("ContactService - start update method");
try {
// contrôle si contact existe
setContact(getContactRepo().findByIdaicontact(contactDTOFront.getIdaicontact()));
if (getContact() == null) {
return false;
}
// alimentation du bean hibernate par le bean dto.
contactDTOFront.alimBean(this);
// maj de la bdd
if (getContactRepo().save(getContact()) == null) {
return false;
}
} catch (Exception ure) {
logger.error("ContactService - Error update method: " + ExceptionUtils.getStackTrace(ure));
return false;
}
return true;
}
All Beans (DTO and entity) are managed in CoreServices Class :
public class CoreServices {
#Autowired
private ContactRepository contactRepo;
// Bean Contact
Contact contact = new Contact();
ContactDTO contactDTO = new ContactDTO();
List<ContactDTO> contactDTOList = new ArrayList<ContactDTO>();
List<Contact> contactList = new ArrayList<Contact>();
public ContactRepository getContactRepo() {
return contactRepo;
}
public Contact getContact() {
return contact;
}
public void setContact(Contact contact) {
this.contact = contact;
}
public ContactDTO getContactDTO() {
return contactDTO;
}
public void setContactDTO(ContactDTO contactDTO) {
this.contactDTO = contactDTO;
}
public List<ContactDTO> getContactDTOList() {
return contactDTOList;
}
public void setContactDTOList(List<ContactDTO> contactDTOList) {
this.contactDTOList = contactDTOList;
}
public List<Contact> getContactList() {
return contactList;
}
public void setContactList(List<Contact> contactList) {
this.contactList = contactList;
}
To set Contact bean , I use "alimBean" method defined in DTO OBject. This method is called in my service.
public void alimBean(CoreServices service) throws Exception {
logger.info("ContactDTO - start alimBean method");
service.getContact().setIdaicontact(this.getIdaicontact());
service.getContact().setIdentifiant(this.getIdentifiant());
service.getContact().setIdaisite(this.getIdaisite());
service.getContact().setIdaitype(this.getIdaitype());
service.getContact().setNom(this.getNom());
service.getContact().setPrenom(this.getPrenom());
service.getContact().setEmail(this.getEmail());
service.getContact().setComment(this.getComment());
service.getContact().setStatus(this.getStatus());
service.getContact().setLocked(this.getLocked());
service.getContact().setUserlock(this.getUserlock());
service.getContact().setCreuser(this.getCreuser());
service.getContact().setUpduser(this.getUpduser());
// Gestion des dates STRING -> DATE
logger.info("ContactDTO - end alimBean method");
}
Now, assuming two update requests are handled in same time. How does it work ?
I read some Tuto about "synchronization" but they are a little confused for me. I don't know if it's the best way and I don't want to break all the code except if it's the only solution to handle this multithreading case
What can I add to this code to be sure the second request will not set Contact object before the first request ended.

Answer 1

You should synchronize only update and delete actions with for example id if it's unique. You can use my library but it's in alfa version but it is tested and works good.
You must add the dependency:
<dependency>
<groupId>com.jsunsoft.util</groupId>
<artifactId>concurrent</artifactId>
<version>0.0.1-alpha2</version>
</dependency>
and write code like this
import com.jsunsoft.util.concurrent.locks.Lock;
public class ContactService extends CoreServices {
private final Lock contactLock = new StripedLock(minimumNumberOfStripes, lockTimeSec);
public boolean update(ContactDTO contactDTOFront) {
logger.info("ContactService - start update method");
try {
updateSynched(contactDTOFront);
} catch (Exception ure) {
logger.error("Co: " + ExceptionUtils.getStackTrace(ure));
return false;
}
return true;
}
//you can add the method updateSynched
private void updateSynched(ContactDTO contactDTOFront) throws Exception {
contactLock.lock(contactDTOFront.getId(), () -> {
setContact(getContactRepo().findByIdaicontact(contactDTOFront.getIdaicontact()));
if (getContact() == null) {
throw new Exception("msg");
}
// alimentation du bean hibernate par le bean dto.
contactDTOFront.alimBean(this);
// maj de la bdd
if (getContactRepo().save(getContact()) == null) {
throw new Exception("msg");
}
});
}
}
Note: In that library I used the guava striped lock if you want you can use directly the guava API.