Spring Data JPA 更新行而不获取行 ById答案

【问题标题】：Spring Data JPA update a Row without getting the row ByIdSpring Data JPA 更新行而不获取行 ById
【发布时间】：2019-09-05 14:33:05
【问题描述】：

我想使用 spring-jpa 更新表格

这是我的实体类

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;

}

我有一个低于Json Input 的PutMapping Spring boot API

{
    "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
}

我的控制器将Principal 对象用于创建和更新rewards 表

@PutMapping
    public ResponseEntity<RewardsResponse> updateRewards(Principal updatedPrincipal,
                                                                   @RequestBody RewardUpdateRequest RewardUpdateRequest) {

但我不会从我的 Angular-UI 发送我的 createdId 或 updatedId。所以当我尝试使用下面的服务层代码将更新的实体插入到表中时

 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);
}

我收到以下错误

could not execute statement; SQL [n/a]; constraint [created_id]; nested exception is org.hibernate.exception.ConstraintViolationException: could not execute statement

我的假设是RewardEntity 通过映射我们传递的ID 并仅更新我设置的fields 而不会触及其余字段...

我是否应该首先根据 ID 从数据库中获取我的 RewardEntity 对象，然后在其之上进行更新？这使得代码每次更新都连接数据库两次。

请提出您的意见

【问题讨论】：

RTFM

标签： spring spring-boot jpa spring-data-jpa

【解决方案1】：

我会首先使用updatedId获取参考对象

RewardEntity rewardEntity = rewardRepository.getOne(updatedId )

根据您的要求更新此对象

rewardEntity.setLastModifiedDate(OffsetDateTime.now());

最后使用 save 来更新它。

return rewardRepository.save(rewardEntity);

getOne() 返回对实体的引用并在内部调用EntityManager.getReference() 方法。它总是会返回一个代理而不访问数据库（延迟获取）。

【讨论】：