对象持久和java-深入的了解面向对象语言中的对象持久的讨论
对象持久和java-深入的了解面向对象语言中的对象持久的讨论(中文3600字,英文2700字)
对象持久化这个术语你常常会和数据存储一起听到。持久化被期望用于事务完整性和更严格的条件(参看文献部分获取更多的事务处理的信息)。但是,编程语言提供的标准类库和包都没有包含事务约束。正如本文中我们将清楚的看到简单的java持久化很有可能会滋生语言本身,而复杂的数据库功能将由数据库厂商提供。
没有对象是一个岛屿
在真实的世界,你很少发现一个事物跟其它事物之间没有关系,事物是对象模型的成分。对事物的持久化比对对象模型的持久化要困难,而且我们可以观察到对象之间是通过他们之间的关系关联在一起的。关联方式的数据存储趋于根据类型进行数据汇总,表中的行表示硬盘上同一种类型对象的物理存储,对象之间的关系是通过多张表共享关键字来表现的。虽然通过数据库组织,关系数据库有时允许多个表能使用同一逻辑块来组成群集,例如,一个数据库部分,它没有机制存储对象关系。为此,为了构建一个对象模型,这些关系从进程运行时已经存在的关键字被构建的,也被称作表连接。这同样是众所周知的关系数据库的一个特性叫做“数据独立性”。几乎所有的对象数据库都提供一些机制来增强系统的性能,包括复杂的对象关系,都超过传统的关系数据库。 [资料来源:http://Doc163.com]
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外文原文(复印件)
Object persistence and Java
Get an in-depth look at the issues surrounding object persistence in object-oriented languages
Object durability, or persistence, is the term you often hear used in conjunction with the issue of storing objects in databases. Persistence is expected to operate with transactional integrity, and as such it is subject to strict conditions. (See the Resources section of this article for more information on transaction processing.) In contrast, language services offered through standard language libraries and packages are often free from transactional constraints.
As we'll see in this article, evidence suggests that simple Java persistence will likely stem from the language itself, while sophisticated database functionality will be offered by database vendors.
No object is an island
In the real world, you rarely find an object that lacks relations to other objects. Objects are components of object models. The issue of object durability transcends the issue of object model durability and distribution once we make the observation that objects are interconnected by virtue of their relations to one another.
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