Hibernate

Architecture

  flowchart TB
	App[Java Application]
	PO[Persistence Objects]
	subgraph Hibernate
	T[Transaction]
	C[Configuration]
	SF[Session_Factory]
	S[Session]
	Q[Query]
	FLC[First_Level_Cache]
	end
	SLC[Second_Level_Cache]
	DB[(Database)]

	App --> PO

	S --> PO

	SF --> C
	S --> SLC

	S --> Q --> FLC

	Hibernate --> DB

	S -->  SF

• Configuration Object : Holds configuration properties of Hibernate

  • Two Components
    • Database Connection
    • 配置 class 的映射

• SessionFactory Object : 由 Configuration Object 實例化

  • client : ConnectionProvider
  • Holds second-level cache(optional)
  • can one SessionFactory per database

• Session Object :

• Short-Lived Object : 此物件(也是個Factory)包含

  • JDBC Connection
  • org.hibernate.Session interface provides methods
    • insert
    • update
    • delete
    • First-Level Cache of data

• Transaction interface :

• Query interface :

• Criteria :

Lifecycle

  flowchart TB

		O((Object))
		TS(Transient_State)
		PS(Persistent_State)
		DS(Detached_Sate)
		RS(Removed_Sate)
		E((End))

		O --->|New isntance of entiy| TS
		O --->|get,load| PS

		TS --->|save,persist,saveOrUpdate,update| PS
		TS --->|Garbage| E

		PS --->|delete| RS
		PS --->|detach,close,clear,evict| DS

		DS --->|save,saveOrUpdate,merge,lock| PS
		DS --->|Garbage| E

Transient State

• The object is not associated with any Hibernate session
• The object is simply a plain Java object (POJO) that is not yet persisted in the database.

Persistent State

Two sub-states of the persistent state

Transient->Persistent State

Persistent->Detached State

Detached State

Removed State

First-Level Cache

Pros

• 減少 JDBC 的 boiler-plate code
• Hibernate Cache 提供更好的 performance
• 提供 Proxy Object 來支援 Lazy Init