db4o

Get ready to learn how db4o supports application security , distribution , and transactions .

了解db4o如何支持应用程序安全性、分布和事务。

Now let 's find out what happens in a db4o database when the code changes .

现在我们来看看当代码发生改变时db4o数据库的反应。

In this series , I have introduced the essentials of object-oriented data management with db4o .

在本系列中，我介绍了使用db4o进行面向对象数据管理的基本要素。

If you haven 't already done so , you may want to download db4o now .

如果您还没有下载db4o，可能希望立即下载。

That same flexibility also makes db4o a good candidate for inclusion in a test-driven development process .

这样的灵活性也使得db4o非常适合于测试驱动开发过程。

Feel free to add to the tests however you like to test other aspects of the db4o API .

可以自由地添加，以测试您想测试的其他db4oAPI特性。

Only fields and the name of the class itself ( discussed next ) are of any importance to db4o .

只有字段和类名本身（接下来会进行讨论）对于db4o才是重要的。

Accordingly , when you call set , db4o knows to update the existing object rather than insert a new one .

相应地，当调用set时，db4o将会更新现有的对象而不是插入新对象。

The solution is to encrypt the file , which in db4o is relatively straightforward .

解决方案是对文件进行加密，这在db4o中比较简单。

In this article , you 've seen some initial examples of adjusting complex code to account for db4o 's object model .

在本文中，您看到了一些基本例子，通过调整复杂代码来实现db4o对象模型。

Understanding how an OODBMS like db4o stores associated objects held through references is a tricky business .

理解像db4o这样的OODBMS是如何通过引用存储相关对象，是比较复杂的事情。

The downside of this sort of operation is that db4o could accidentally truncate a value .

这种操作的缺点是，db4o可能会意外地将一个值截尾。

I demonstrated data retrieval using db4o 's QBE engine last time , but I 'll quickly recap here .

上一次我使用了db4o的QBE引擎演示了数据检索，这里将快速回顾一下。

Fortunately , there are a couple of ways to teach db4o how to manage the transition .

幸运的是，有两种方法可以教会db4o如何管理这样的转换。

But please don 't repeat that name to the db4o developers ; you 'll get me in trouble .

（如果愿意的话，可以称之为“JQL”&JavaQueryLanguage，不过请不要向db4o开发人员转述这个名字，这会给我带来麻烦）。

Last month , I talked about querying db4o using both native and QBE-style queries .

上个月，我谈到了使用原生和QBE样式的查询来查询db4o。

Let db4o tell you

让db4o告诉您

Db4o can take care of all aspects of data administration , e.g.when you update your software with a new data model over the air .

db4o能承担各种不同方面的数据管理工作，例如，当你使用无线方式更新软件的一个新的数据模型时，db4o就能很好地适应和管理。

The key thing to remember is that you can build convenience methods on top of the db4o infrastructure to make it easier to use .

关键要记住可以在db4o基础架构之上构建方便的方法，从而使db4o更加易于使用。

Actually , db4o 's knack for backward-compatibility deserves a bit more explanation .

实际上，db4o向后兼容的妙法值得解释一下。

This time , I 'll continue that theme the many options found in db4o with a look at how it handles refactoring .

这一次，我将继续这一主题db4o的众多选项看看db4o如何处理重构。

In particular , I 'll introduce the various mechanisms available for retrieving , modifying , and restoring objects back into db4o .

特别是，我将介绍用于检索、修改并将对象重新存储到db4o的各种可用机制。

A query API for db4o is available in the form of SODA queries , which are used principally for fine-grained query control .

db4o的查询API可以使用SODA形式，这种形式主要用于细粒度查询控制。

Something like this is a drastic change to db4o because it stores objects in a manner that keys off of classname .

像这样的更改对于db4o是比较大的更改，因为它需要根据classname来存储对象。

Addressing this at a more granular level currently isn 't an option in db4o , though other OODBMS systems may be more flexible .

目前db4o还不支持更加粒度化级别的解决方式，其他OODBMS系统可能更加灵活。

Within the db4o system , it is trivial to open a second logical connection to the database , even when the database resides on the local disk .

在db4o系统中，打开第二个数据库逻辑连接非常简单，即使当数据库驻留在本地磁盘上时也是如此。

The most important thing here is that db4o silently handled the mismatch between what it saw on the disk and in the type definition .

这里最重要的一点是，db4o静默地处理它看到的磁盘上的数据与类型定义之间的不匹配。

It 's important to track what 's happening because , as you know , the db4o system keeps references to objects it has already opened along the way .

需要对发生的行为进行跟踪，因为db4o需要一直保持对打开对象的引用。

Defining access control in db4o consists of nothing more than the grantAccess () method , and it grants access to the entire database instance .

要在db4o中定义访问控制，只需使用grantAccess（）方法，它授权对整个数据库实例的访问。

Client-side applications that can adapt automatically over time ( as db4o detects and adjust to schema changes ) and can collaborate and share data among different applications .

客户端应用能适应自动超时，因为db4o能检测、并在schema变化时进行调整；还能在不同的应用间协作和共享数据。