Introduction to ORM with Spring

Easier testing. Spring 的 IoC 方法可以很容易地交换 Hibernate SessionFactory 实例、JDBC DataSource 实例、事务管理器和映射对象实现（如果需要）的实现和配置位置。而这反过来又使得更加容易单独测试每段与持久性相关的代码。

Easier testing. Spring’s IoC approach makes it easy to swap the implementations and configuration locations of Hibernate SessionFactory instances, JDBC DataSource instances, transaction managers, and mapped object implementations (if needed). This in turn makes it much easier to test each piece of persistence-related code in isolation.

Common data access exceptions. Spring 可以封装 ORM 工具抛出的异常，将它们从专有（可能是已检查）异常转换为一个通用的运行时 DataAccessException 层次结构。此功能允许您仅在适当的层中处理大多数不可恢复的持久性异常，而无需烦人的样板化 catch、throws 和异常声明。您仍然可以根据需要捕捉并处理异常。请记住，JDBC 异常（包括特定于数据库的方言）也会转换为相同的层次结构，这意味着您可以在一致编程模型中使用 JDBC 执行一些操作。

Common data access exceptions. Spring can wrap exceptions from your ORM tool, converting them from proprietary (potentially checked) exceptions to a common runtime DataAccessException hierarchy. This feature lets you handle most persistence exceptions, which are non-recoverable, only in the appropriate layers, without annoying boilerplate catches, throws, and exception declarations. You can still trap and handle exceptions as necessary. Remember that JDBC exceptions (including DB-specific dialects) are also converted to the same hierarchy, meaning that you can perform some operations with JDBC within a consistent programming model.

General resource management. Spring 应用程序上下文可以处理 Hibernate SessionFactory 实例、JPA EntityManagerFactory 实例、JDBC DataSource 实例和其他相关资源的位置和配置。这使得管理和更改这些值变得很容易。Spring 提供了持久性资源的高效、简单且安全的处理方法。例如，通常使用 Hibernate 的相关代码需要使用同一个 Hibernate Session 来确保效率和正确的交易处理。Spring 可以轻松地创建 Session 并将其透明地绑定到当前线程，通过 Hibernate SessionFactory 公开当前 Session。因此，Spring 解决了许多典型的 Hibernate 使用中的长期问题，适用于任何本地或 JTA 交易环境。

General resource management. Spring application contexts can handle the location and configuration of Hibernate SessionFactory instances, JPA EntityManagerFactory instances, JDBC DataSource instances, and other related resources. This makes these values easy to manage and change. Spring offers efficient, easy, and safe handling of persistence resources. For example, related code that uses Hibernate generally needs to use the same Hibernate Session to ensure efficiency and proper transaction handling. Spring makes it easy to create and bind a Session to the current thread transparently, by exposing a current Session through the Hibernate SessionFactory. Thus, Spring solves many chronic problems of typical Hibernate usage, for any local or JTA transaction environment.

Integrated transaction management. 您可以通过 @Transactional 注释或在 XML 配置文件中明确配置事务 AOP 建议，使用声明性面向切面编程 (AOP) 样式方法拦截器，封送您的 ORM 代码。在这两种情况下，都会为您处理事务语义和异常处理（回滚等）。正如 Resource and Transaction Management 中讨论的那样，您还可以交换各种事务管理器，而不会影响您相关的 ORM 代码。例如，您可以在本地事务和 JTA 之间进行交换，并且在两种情况下都提供相同的完整服务（如声明性事务）。此外，与 JDBC 相关的代码可以与您用于执行 ORM 的代码完全集成。这对于不适合 ORM 的数据访问（如批量处理和 BLOB 流处理）很有用，但仍需要与 ORM 操作共享公共事务。

Integrated transaction management. You can wrap your ORM code with a declarative, aspect-oriented programming (AOP) style method interceptor either through the @Transactional annotation or by explicitly configuring the transaction AOP advice in an XML configuration file. In both cases, transaction semantics and exception handling (rollback and so on) are handled for you. As discussed in Resource and Transaction Management, you can also swap various transaction managers, without affecting your ORM-related code. For example, you can swap between local transactions and JTA, with the same full services (such as declarative transactions) available in both scenarios. Additionally, JDBC-related code can fully integrate transactionally with the code you use to do ORM. This is useful for data access that is not suitable for ORM (such as batch processing and BLOB streaming) but that still needs to share common transactions with ORM operations.