[Core]1 详解Hibernate下对象状态和Session接口.docxVIP

A、Session接口public interface Session extends Serializableorg.hibernate.SessionThe main runtime interface between a Java application and Hibernate. This is the central API class abstracting the notion of a persistence service.它是java应用程序和hibernate之间主要的运行时接口。这个中心API类抽象了一个持久服务的概念。The lifecycle of a Session is bounded by the beginning and end of a logical transaction. (Long transactions might span several database transactions.)Session的生命周期由一个逻辑事务限制。（长的事务可能要跨度几个数据库事务）。The main function of the Session is to offer create, read and delete operations for instances of mapped entity classes. Instances may exist in one of three states:transient: never persistent, not associated with any Sessionpersistent: associated with a unique Sessiondetached: previously persistent, not associated with any SessionSession的主要功能是为一个映射实体类的实例提供创建，读取，删除操作。这个实例可以是下面三种状态中的一种：transient: 没有持久化，不和任何Session相关联。persistent: 和一个Session相关联。detached: 之前持久化过，但不和任何Session相关联。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().Transient（瞬时）实例可以通过save(), persist() or saveOrUpdate()来进行实例化。Persistent（持久）实例可以通过调用delete()来变成Transient（瞬时）实例。任何由get()或 load()方法返回的实例都是Persistent（持久）实例。Detached（托管）实例可通过调用update(), saveOrUpdate(), lock()或replicate()来变成Persistent（持久）实例。一个Transient（瞬时）或Detached（托管）实例的状态也可以通过调用merge()来变成Persistent（持久）状态。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 are detected at flush time and also result in an SQL UPDATE. saveOrUpdate() and replicate() result in either an INSERT or an UPDATE.save()和persist()的结果是INSERT SQL代码