Hibernate 3.3.2中文参考指南：关系数据库持久化实战

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"hibernate3.32_referenc_ZHCN" 这篇文档是Hibernate 3.3.2 GA版本的中文参考指南，由Gavin King、Christian Bauer、Max Rydahl Andersen、Emmanuel Bernard和Steve Ebersole等人撰写，并感谢James Cobb、Cheyenne Weaver和Cao Xiaogang在设计方面的贡献。文档旨在帮助Java开发者理解和使用Hibernate，这是一个流行的对象关系映射（ORM）框架，用于简化数据库持久化的复杂性。文档分为多个部分，首先介绍了如何提供反馈，然后逐步引导读者通过一个教程来学习Hibernate。在教程的第一部分，讲述了如何设置第一个Hibernate应用程序，包括创建类、映射文件、配置Hibernate以及使用Maven构建项目。这部分还涉及启动和辅助类的编写，以及如何加载和存储对象。第二部分深入到关联映射，讲解了如何映射Person类以及不同类型的关联，如单向Set-based关联、值类型的集合和双向关联。这部分还涵盖了如何使这些关联在程序中正确工作。第三部分是一个名为EventManager的Web应用程序示例，讲解了如何编写基本的Servlet，处理事务边界，以及如何部署和测试应用。特别提到了"session-per-request"模式，这是一种常见的事务管理策略，确保每个HTTP请求对应一个数据库会话，如果在处理请求过程中出现错误，会自动回滚事务。此外，建议使用servlet过滤器来简化事务管理代码。接下来，文档探讨了Hibernate的体系结构，包括概述、实例状态、与Java Management Extensions (JMX)的整合、对Java Connection Administration (JCA)的支持，以及上下文会话的概念。这部分内容对于理解Hibernate的工作原理和如何与其他企业级技术集成至关重要。最后，配置章节详细阐述了如何编程式地配置Hibernate，包括设置数据源、实体管理器工厂、会话工厂等，以及如何定义属性和属性值。这部分对于实际项目中的配置工作非常实用。这份中文文档全面覆盖了Hibernate的基础知识和高级特性，是Java开发者学习和使用Hibernate的重要参考资料。通过学习，开发者可以掌握如何将Java对象与数据库表进行映射，有效地管理数据库事务，以及如何配置和优化Hibernate应用。

第1章Tutorial

private void setId(Long id) {

this.id = id;

}

public Date getDate() {

return date;

}

public void setDate(Date date) {

this.date = date;

}

public String getTitle() {

return title;

}

public void setTitle(String title) {

this.title = title;

}

This class uses standard JavaBean naming conventions for property getter and setter

methods, as well as private visibility for the fields. Although this is the recommended

design, it is not required. Hibernate can also access fields directly, the benefit of

accessor methods is robustness for refactoring.

The id property holds a unique identifier value for a particular event. All persistent

entity classes (there are less important dependent classes as well) will need such an

identifier property if we want to use the full feature set of Hibernate. In fact, most

applications, especially web applications, need to distinguish objects by identifier,

so you should consider this a feature rather than a limitation. However, we usually do

not manipulate the identity of an object, hence the setter method should be private. Only

Hibernate will assign identifiers when an object is saved. Hibernate can access public,

private, and protected accessor methods, as well as public, private and protected fields

directly. The choice is up to you and you can match it to fit your application design.

The no-argument constructor is a requirement for all persistent classes; Hibernate

has to create objects for you, using Java Reflection. The constructor can be private,

however package or public visibility is required for runtime proxy generation and

efficient data retrieval without bytecode instrumentation.

Save this file to the src/main/java/org/hibernate/tutorial/domain directory.

Hibernate配置

</id>

</class>

</hibernate-mapping>

Similar to the id element, the name attribute of the property element tells Hibernate

which getter and setter methods to use. In this case, Hibernate will search for getDate(),

setDate(), getTitle() and setTitle() methods.

注意

Why does the date property mapping include the column attribute, but the

title does not? Without the column attribute, Hibernate by default uses

the property name as the column name. This works for title, however, date

is a reserved keyword in most databases so you will need to map it to

a different name.

The title mapping also lacks a type attribute. The types declared and used in the mapping

files are not Java data types; they are not SQL database types either. These types are

called Hibernate mapping types, converters which can translate from Java to SQL data

types and vice versa. Again, Hibernate will try to determine the correct conversion

and mapping type itself if the type attribute is not present in the mapping. In some

cases this automatic detection using Reflection on the Java class might not have the

default you expect or need. This is the case with the date property. Hibernate cannot

know if the property, which is of java.util.Date, should map to a SQL date, timestamp,

or time column. Full date and time information is preserved by mapping the property

with a timestamp converter.

提示

Hibernate makes this mapping type determination using reflection when the

mapping files are processed. This can take time and resources, so if

startup performance is important you should consider explicitly defining

the type to use.

Save this mapping file as src/main/resources/org/hibernate/tutorial/domain/Event.hbm.xml.

1.1.4.Hibernate配置

At this point, you should have the persistent class and its mapping file in place. It

is now time to configure Hibernate. First let's set up HSQLDB to run in "server mode"

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