我确实有两个名为 School 和 Level 的实体,具有多对多关系。
@Data
@Entity
public class School {
@Id
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "school_generator")
@SequenceGenerator(name="school_generator", sequenceName = "school_seq", allocationSize=1)
@Column(name = "school_id")
private Long id;
@NotBlank
private String name;
@NotBlank
private String city;
@ManyToMany(cascade = {CascadeType.PERSIST, CascadeType.MERGE})
@JoinTable(
name = "school_level",
joinColumns = @JoinColumn(name = "school_id"),
inverseJoinColumns = @JoinColumn(name = "level_id"))
private Set<Level> levels = new HashSet<>();
}
@Data
@Entity
public class Level implements Serializable {
@Id
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "level_generator")
@SequenceGenerator(name = "level_generator", sequenceName = "level_seq", allocationSize = 1)
@Column(name = "level_id")
private Long id;
@NotBlank
@Column(nullable = false, unique = true)
private String name;
}
我的 SchoolController
(Rest Controller )有一个 create 方法,该方法采用 SchoolDTO(目前它具有与实体相同的结构)。
当我发布 DTO 时,嵌套子列表级别仅使用现有级别 ID 填充(因为之前创建了级别)。
当我尝试通过 JPARepository 保存方法进行保存时...抛出此消息的异常:
"detached entity passed to persist: com.salimrahmani.adawat.domain.Level; nested exception is org.hibernate.PersistentObjectException: detached entity passed to persist: com.salimrahmani.adawat.domain.Level",
"trace": "org.springframework.dao.InvalidDataAccessApiUsageException: detached entity passed to persist:
通过迭代每个级别 Id 可以解决问题...使用 JPA 存储库方法 getOne
(调用 entityManager.getReference
)获取引用
然后加载正确的模型,然后坚持成功。
@PostMapping("/{id}/grades")
public ResponseEntity<SchoolDTO> addLevelToPackage(@PathVariable Long id, @RequestBody @Valid LevelDTO levelDTO) {
return schoolService.findById(id)
.map(school -> {
Level level = levelMapper.map(levelDTO);
if(level.getId() != null) {
level = levelService.getOne(level.getId());
school.getLevels().add(level);
} // else error
School saved = schoolService.save(school);
return ResponseEntity.ok(schoolMapper.map(saved));
}).orElseGet(() -> ResponseEntity.notFound().build());
}
我的问题是:这是在 Spring Data 中发布关联的“唯一”正确方法吗?或者有什么更好的办法吗?
最佳答案
在addLevelToPackage
函数中为什么要使用map
schoolService.findById(id).map..
如果我认为schoolService会返回只有一个具有给定 ID 的实体 School 实例。
我认为用以下内容替换 map 就足够了:
...
School theSchool = schoolService.findById(id);
Level theLevel = levelService.getOne(levelDTO.getId());
theSchool.getLevels().add(theLevel);
School saved = schoolService.save(theSchool);
return ResponseEntity.ok(schoolMapper.map(saved));
...
关于java - Spring Data JPA - 使用现有的嵌套子对象保留新对象,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/60458490/