Hibernate-翻译

Hibernate 架构In layman’s terms, Hibernate sits between your application and database and provide the persistence for your application via set of API’s, performing transformation(based on defined metadata) transparently between java objects and database representation.通俗地说，Hibernate是在你的应用程序和数据库之间通过一系列API接口来持久化你的应用程序，在Java对象和数据库之间执行转换（基于元数据）。

Hibernate functionality/flow/usage can be described as follows:Hibernate 功能/流程/使用可以描述如下：On Application startup, hibernate reads it configurationfile(hibernate.cfg.xml or hibernate.properties) which contains information required to make the connection with underlying database and mappinginformation. Based on this information, hibernate creates ConfigurationObject , which in turns creates SessionFactory which acts as singleton for the whole application.∙在应用程序运行时，Hibernate读取它的配置文件（hibernate.cfg.xml或hibernate.properties）包含用来连接基础数据库和映射的必需信息。

在这个信息的基础上，hibernate生成实体配置，这个动作将独立的为整个程序创建SessionFactory。

∙Hibernate creates instances of entity classes.Entity classes are java classes which are mapped to the database table usingmetadata(XML/Annotaitons).These instances are called transient objects as they are not yet persisted in database.∙Hibernate 创建实体类的实例，实体类是映射到数据库表元数据（XML/Annotation）的Java类。

∙To persist an object, application ask for a Session from SessionFactory which is a factory for Session.Session represent a physical database connection.∙为了持久化一个对象，程序通过SessionFactory发送一个Session请求。

Session 代表一个物理数据库连接。

∙Application then starts the transaction to make the unit of work atomic, & uses Session API’s to finally persist the entity instance indatabase.Once the entity instance persisted in database, it’s knownas persistent object as it represent a row in database table.Application then closes/commits the transaction followed by session close.∙当程序启动事物并使用Session接口将实体实例保存到数据库中。

一旦这个实体被保存到数据库中，它被称为持久化对象，因为它代表了数据库表中的一行。

当session关闭时，程序也关闭/托管这个事物。

∙Once the session gets closed , the entity instance becomes detatched which means it still contains data but no more attached to the database table & no more under the management of Hibernate. Detatched objects can again become persistent when associated with a new Session, or can be garbage collected once no more used.∙一旦这个session关闭，这个持久化对象将变为独立的，这意味着它任然包含数据，但是不再附属在数据库表中，并不再处于Hibernate管理之中。

当打开一个新的Session时这个独立的对象可以再次持久化，一旦不再使用将被回收。

Below is the brief description of commonly used core API’s in a typical application persistence with Hibernate.下面将简单的描述，在一个典型的程序中使用核心API接口进行Hibernate的持久化。

It allows the application on startup, to specify properties and mapping documents to be used when creating a SessionFactory. Properties file contains database connection setup info while mapping specifies the classes to be mapped.它允许应用程序在启动时，使用映射文件指定的属性创建一个SessionFactory。

属性文件包含数据库连接配置、指定映射的类。

It’s a thread-safe immutable object created per database & mainly used for creating Sessions.It caches generated SQL statements and other mapping metadata that Hibernate uses at runtime.它是一个创建数据库时线程安全的不可改变的对象，并且主要用来创建Sessions。

在运行时通过Hibernate映射元数据生成的SQL语句。

It’s a single-threaded object used to perform create, read, update and delete operations for instances of mapped entity classes. Since it’s not thread-safe, it should not be long-lived and each thread/transaction should obtain its own instance from a SessionFactory.它是一个单线程执行对映射实体类的实例进行创建，读取，更新和删除的操作。

它不是线程安全的，不应该持久存在，每个线程/事务应该通过SessionFactory获取它自己的实例。

It’s a single-thread object used by the application to define units of work. A transaction is associated with a Session. Transactions abstract application code from underlying transaction implementations(JTA/JDBC), allowing the application to control transaction boundaries via a consistent API. It’s an Optional API and application may choose not to use it.它是一个单线程对象，可以定义为程序工作单元。

transaction和Session相关联。

对抽象程序代码基础事务实现（JTA/JDBC），允许程序通过一致的接口控制事务边界。

它是一个可选接口并且程序可以不选择使用它。

A single-thread object used to perform query on underlying database. A Session is a factory for Query. Both HQL(Hibernate Query Language) & SQL can be used with Query object.一个单线程对象用来执行数据库查询。

一个Session是一个查询工厂。

HQL和SQL都可以用来查询。

It is an alternative to HQL , very useful for the search query involving multiple conditions.它是一个可供替代的HQL，对于涉及多个条件查询非常有用。

Configuring Hibernate配置 HibernateAs mentioned above, the very first task a typical Hibernate application does , is it creates the Configuration Object which will eventually create SessionFactory. Configuration Object needs information pertaining to database connection & mapping(XML or Annotations). There are several approaches to provide this information to Hibernate:如上所述，第一步是一个典型的Hibernate程序，它创建配置对象最终将创SessionFactory。