org.hibernate.cfg Class Configuration
An instance of Configuration allows(允许) the application to specify properties and mapping documents to be used when creating a SessionFactory. Usually an application will create a single Configuration, build a single instance of SessionFactory and then instantiate Sessions in threads servicing client requests. The Configuration is meant(意味着) only as an initialization-time object. SessionFactorys are immutable anddo not retain(不保留) anyassociation(关联) back to the Configuration.
A new Configuration will use the properties specified in hibernate.properties by default.
buildSessionFactory
Instantiate a new SessionFactory, using the properties and mappings in this configuration. The SessionFactory will be immutable, so changes made to the Configuration after building the SessionFactory will notaffect(影响) it.
org.hibernate Interface SessionFactory
The main contract here is the creation of instances. Usually an application has a single instance and threads servicing client requests obtain(获得,得到) instances from this factory.
The internal state of a is immutable. Once(一旦) it is created this internal state isset(设置的). This internal state includes all of themetadata(元数据)about Object/Relational Mapping.
Implementors must be threadsafe.
org.hibernate Interface Session
The main runtime interface between a Java application and Hibernate. This is the central API class abstracting the notion(概念) of a persistence(持久化) service.
The lifecycle(生命周期) of a Session is bounded(有界限) by the beginning and end of a logical(逻辑) transaction. (Long transactions might span(跨越,持续,有) several(多个) database transactions.)
The main function(功能,用途,函数) of the Session is to offer(提供) create, read and delete operations for instances of mapped entity classes. Instances may exist in one of three states:transient(短暂的,瞬时的): never persistent(持续,持久,固执的), not associated(关联) with any Sessionpersistent: associated with(与..相关) a unique Sessiondetached(分离的): previously(以前) persistent, not associated with any Session Transient instances may be made persistent by calling save(), persist() or saveOrUpdate(). Persistent instances may be made transient by calling delete(). Any instance returned by a get() or load() method is persistent. Detached instances may be made persistent by calling update(), saveOrUpdate(), lock() or replicate(). The state of a transient or detached instance may also be made persistent as a new persistent instance by calling merge().save() and persist() result in an SQL INSERT, delete() in an SQL DELETE and update() or merge() in an SQL UPDATE. Changes to persistent instances aredetected(检测到) at flush time and also result in an SQL UPDATE. saveOrUpdate() and replicate() result in either(任何一个) an INSERT or an UPDATE.It is not intended that implementors be threadsafe. Instead(相反) each thread/transaction shouldobtain(获得,获取) its own instance from a SessionFactory.A Session instance is serializable if its persistent classes are serializable.
A typical(典型的) transaction should use the following idiom:
Session sess = factory.openSession(); Transaction tx; try { tx = sess.beginTransaction(); //do some work ... tx.commit(); } catch (Exception e) { if (tx!=null) tx.rollback(); throw e; } finally { sess.close(); } If the Session throws an exception, the transaction must be rolled back and the session discarded(废弃,丢弃) . The internal state of the Session might not be consistent(不一致) with the database after the exception occurs(发生) .