Spring Data JPA update a Row without getting the row ById - spring

Question

I want to update the table using spring-jpa
This is my Entity Class
public class RewardEntity {
#Id
#Column(name = "reward_id", columnDefinition = "bigserial")
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long rewardId;
#Column(name = "reward_title", nullable = false)
private String rewardTitle;
#Column(name = "reward_text")
private String rewardText;
#Column(name = "reward_type", nullable = false)
private String rewardType;
#Column(name = "reward_for_code", nullable = false)
private String rewardFor;
#Column(name = "reward_from_date", nullable = false)
private OffsetDateTime rewardFromDate;
#Column(name = "reward_to_date", nullable = false)
private OffsetDateTime rewardToDate;
#Column(name = "is_display_on", nullable = false)
private Boolean isDisplayOn;
#Column(name = "created_id", length = 50, nullable = false)
private String createdId;
#Column(name = "updated_id", length = 50)
private String updatedId;
#Column(name = "created_date", columnDefinition = "timestamptz", nullable = false)
private OffsetDateTime createdDate;
#Column(name = "last_modified_date", columnDefinition = "timestamptz")
private OffsetDateTime lastModifiedDate;
}
I have a PutMapping Spring boot API that gets below Json Input
{
"rewardId": 53,
"rewardTitle": "Reward is Allocated",
"rewardText": "Reward allocated for your recent purchase with our shop located at ABC-Mall",
"rewardType": "Informational",
"rewardFor": "Customer",
"rewardFromDate": "2019-04-12T00:00:00+05:30",
"rewardToDate": "2019-04-15T00:00:00+05:30",
"isDisplayOn": false
}
My Controller takes Principal object for both creation and updating the rewards table
#PutMapping
public ResponseEntity<RewardsResponse> updateRewards(Principal updatedPrincipal,
#RequestBody RewardUpdateRequest RewardUpdateRequest) {
But I won't send my createdId or updatedId from my Angular-UI.. So when i try to insert the updated-entity in to the table, using the below service-layer code
public RewardEntity updateReward(Principal principal, rewardEntity rewardEntity) {
String updatedId = null != principal ? principal.getName() : "defaultUpdatedId";
rewardEntity.setUpdatedCdsId(updatedId);
rewardEntity.setLastModifiedDate(OffsetDateTime.now());
return rewardRepository.save(rewardEntity);
}
I get the below error
could not execute statement; SQL [n/a]; constraint [created_id]; nested exception is org.hibernate.exception.ConstraintViolationException: could not execute statement
My assumption is that RewardEntity gets updated in the same row by mapping the ID that we pass and update only the fields that i set and do not touch rest of the fields ...
Should i first get my RewardEntity object from the DB based on the ID and then update on top of it ?? This makes the code connect DB twice for every update.
Request your inputs please

Answer 1

I would first get reference object using updatedId
RewardEntity rewardEntity = rewardRepository.getOne(updatedId )
update this object as per your requirement
rewardEntity.setLastModifiedDate(OffsetDateTime.now());
and finally use save to update this.
return rewardRepository.save(rewardEntity);
getOne() returns a reference to the entity and internally invokes EntityManager.getReference() method. It will always return a proxy without hitting the database (lazily fetched).