---
title: Spring Data JPA
tags: Spring, Data JPA
---

## 聯級管理

### OneToMany

* orphanRemoval - 若 Many 方在 One 方修改後無對應的關聯對象，則自動刪除。
* example:

	@OneToMany(mappedBy = "parent", cascade = CascadeType.ALL, orphanRemoval = true)
	private List<Child> children = new ArrayList<>();
	
	修改前
	{
		"id": "parent"
		"children": [
			{"id": 1},
			{"id": 2}
		]
	}
	
	修改後
		{
		"id": "parent"
		"children": [
			{"id": 2}
		]
	}
	
	id = 1 的 child 會一併刪除

* 需要 PERSIST 權限，原因未知。

* Issues
* 若要透過 One 方新增 Many 方，需要給予 MERGE 權限而非 PERSIST。