使用Neo4j OGM更新节点而不先检索它
提问于 2018-02-06 11:23:57
我有一个结构，它(简化的)看起来像这样：
@NodeEntity(label = "Entity")
class FullEntity {
@Id @GeneratedValue
var _id: Long? = null
@Id @Index(unique = true)
lateinit var uuid: String
lateinit var someMoreData: String // this data is sometimes lost
@Relationship(type = "TARGETS", direction = Relationship.OUTGOING)
var target: StubEntity? = null
}
@NodeEntity(label = "Entity")
class StubEntity {
@Id @GeneratedValue
var _id: Long? = null
@Id @Index(unique = true)
lateinit var uuid: String
}
@RepositoryRestResource
interface EntityRepository : Neo4jRepository<FullEntity, Long>现在，当我单独保存两个相关的FullEntity对象时，如果我以一种方式保存，那么它都可以工作：
entityRepository.save(FullEntity().apply {
uuid = "uuid1"
someMoreData = "SomeMoreData1"
target = StubEntity().apply {
uuid = "uuid2"
}
})
// some time later ...
entityRepository.save(FullEntity().apply {
uuid = "uuid2"
someMoreData = "SomeMoreData2"
})但是如果我像这样颠倒顺序：
entityRepository.save(FullEntity().apply {
uuid = "uuid2"
someMoreData = "SomeMoreData2"
})
// some time later ...
entityRepository.save(FullEntity().apply {
uuid = "uuid1"
someMoreData = "SomeMoreData1"
target = StubEntity().apply {
uuid = "uuid2"
}
})它删除了"SomeMoreData2"。
回答 1
Stack Overflow用户
发布于 2018-02-08 07:30:38
我发现你的类和在OGM中的使用有两个问题：
- 你两次使用
Entity这个标签。如果OGM试图从Neo4j加载数据，这将产生问题。它找不到正确的类型来赋值。可能的解决方法：
- Explicitly set the label to another one like `StubEntity` for this class.
- If this is not possible because the uniqueness of the uuid over both classes, you may not even need the `StubEntity` but use the `FullEntity` class also for the relationship target. There will be no difference in Neo4j after saving the data.
- If both classes have more differences than the sample code above shows, you may create an abstract class with the `Entity` label and also provide special type labels (implicit by just annotating with `@NodeEntity` or explicit with the label attribute you are already using) on the implementing classes. Than you could use the uuid constraint in the abstract class.
两次使用@Id注释的
- 。如果只需要索引中的字段和唯一约束(如果我理解正确的话)，则不需要在uuid字段上声明额外的
@Id。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/48641888
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