How do I update an entity using spring-data-jpa?

You can simply use this function with save() JPAfunction, but the object sent as parameter must contain an existing id in the database otherwise it will not work, because save() when we send an object without id, it adds directly a row in database, but if we send an object with an existing id, it changes the columns already found in the database.

public void updateUser(Userinfos u) {
    User userFromDb = userRepository.findById(u.getid());
    // crush the variables of the object found
    userFromDb.setFirstname("john"); 
    userFromDb.setLastname("dew");
    userFromDb.setAge(16);
    userRepository.save(userFromDb);
}

As what has already mentioned by others, the save() itself contains both create and update operation.

I just want to add supplement about what behind the save() method.

https://i.stack.imgur.com/ZCGvJ.png

Ok, let's check the save() implementation at SimpleJpaRepository<T, ID>,

@Transactional
public <S extends T> S save(S entity) {

    if (entityInformation.isNew(entity)) {
        em.persist(entity);
        return entity;
    } else {
        return em.merge(entity);
    }
}

As you can see, it will check whether the ID is existed or not firstly, if the entity is already there, only update will happen by merge(entity) method and if else, a new record is inserted by persist(entity) method.

spring data save() method will help you to perform both: adding new item and updating an existed item.

Just call the save() and enjoy the life :))

Using spring-data-jpa save(), I was having same problem as @DtechNet. I mean every save() was creating new object instead of update. To solve this I had to add version field to entity and related table.

This is how I solved the problem:

User inbound = ...
User existing = userRepository.findByFirstname(inbound.getFirstname());
if(existing != null) inbound.setId(existing.getId());
userRepository.save(inbound);

public void updateLaserDataByHumanId(String replacement, String humanId) {
    List<LaserData> laserDataByHumanId = laserDataRepository.findByHumanId(humanId);
    laserDataByHumanId.stream()
            .map(en -> en.setHumanId(replacement))
            .collect(Collectors.toList())
            .forEach(en -> laserDataRepository.save(en));
}

With java 8 you can use repository's findById in UserService

@Service
public class UserServiceImpl {

    private final UserRepository repository;

    public UserServiceImpl(UserRepository repository) {
        this.repository = repository;
    }

    @Transactional
    public void update(User user) {
        repository
                .findById(user.getId()) // returns Optional<User>
                .ifPresent(user1 -> {
                    user1.setFirstname(user.getFirstname);
                    user1.setLastname(user.getLastname);

                    repository.save(user1);
                });
    }

}

Specifically how do I tell spring-data-jpa that users that have the same username and firstname are actually EQUAL and that it is supposed to update the entity. Overriding equals did not work.

For this particular purpose one can introduce a composite key like this:

CREATE TABLE IF NOT EXISTS `test`.`user` (
  `username` VARCHAR(45) NOT NULL,
  `firstname` VARCHAR(45) NOT NULL,
  `description` VARCHAR(45) NOT NULL,
  PRIMARY KEY (`username`, `firstname`))

Mapping:

@Embeddable
public class UserKey implements Serializable {
    protected String username;
    protected String firstname;

    public UserKey() {}

    public UserKey(String username, String firstname) {
        this.username = username;
        this.firstname = firstname;
    }
    // equals, hashCode
}

Here is how to use it:

@Entity
public class UserEntity implements Serializable {
    @EmbeddedId
    private UserKey primaryKey;

    private String description;

    //...
}

JpaRepository would look like this:

public interface UserEntityRepository extends JpaRepository<UserEntity, UserKey>

Then, you could use the following idiom: accept DTO with user info, extract name and firstname and create UserKey, then create a UserEntity with this composite key and then invoke Spring Data save() which should sort everything out for you.

If your primary key is autoincrement then, you have to set the value for the primary key. for the save(); method to work as a update().else it will create a new record in db.

if you are using jsp form then use hidden filed to set primary key.

Jsp:

Java:

@PostMapping("/update")
public String updateUser(@ModelAttribute User user) {
    repo.save(user);
    return "redirect:userlist";
}

also look at this:

@Override
  @Transactional
  public Customer save(Customer customer) {

    // Is new?
    if (customer.getId() == null) {
      em.persist(customer);
      return customer;
    } else {
      return em.merge(customer);
    }
  }

As mentioned by others answer, method save() is dual function. It can both do save or update, it's automatically update if you provide the id.

for update method in controller class I suggested to use @PatchMapping. below is the example.

#Save method POST

{
    "username": "jhon.doe",
    "displayName": "Jhon",
    "password": "xxxyyyzzz",
    "email": "jhon.doe@mail.com"
}
@PostMapping("/user")
public void setUser(@RequestBody User user) {
    userService.save(user);
}

#Update method PATCH

{
    "id": 1, // this is important. Widly important
    "username": "jhon.doe",
    "displayName": "Jhon",
    "password": "xxxyyyzzz",
    "email": "jhon.doe@mail.com"
}

@PatchMapping("/user")
public void patchUser(@RequestBody User user) {
    userService.save(user);
}

Maybe you're wondering where the id's come from. It comes from the database of course, you want to update the existing data right?

You can see the example below:

private void updateDeliveryStatusOfEvent(Integer eventId, int deliveryStatus) {
    try {
        LOGGER.info("NOTIFICATION_EVENT updating with event id:{}", eventId);
        Optional<Event> eventOptional = eventRepository.findById(eventId);
        if (!eventOptional.isPresent()) {
            LOGGER.info("Didn't find any updatable notification event with this eventId:{}", eventId);
        }
        Event event = eventOptional.get();
        event.setDeliveryStatus(deliveryStatus);
        event = eventRepository.save(event);
        if (!Objects.isNull(event)) {
            LOGGER.info("NOTIFICATION_EVENT Successfully Updated with this id:{}", eventId);
        }
    } catch (Exception e) {
        LOGGER.error("Error :{} while updating NOTIFICATION_EVENT of event Id:{}", e, eventId);
    }
}

Or Update Using Native Query:

public interface YourRepositoryName extends JpaRepository<Event,Integer>{
@Transactional
    @Modifying
    @Query(value="update Event u set u.deliveryStatus = :deliveryStatus where u.eventId = :eventId", nativeQuery = true)
    void setUserInfoById(@Param("deliveryStatus")String deliveryStatus, @Param("eventId")Integer eventId);
}

Use @DynamicUpdate annotation. it is cleaner and you don't have to deal with querying the database in order to get the saved values.