Merging persistence units
Spring 支持使用多个持久化单元。但是，有时您可能希望对您的应用程序进行模块化，但仍确保所有这些模块都运行在单个持久化单元内。为了实现该行为，Spring Data JPA 提供了一个 PersistenceUnitManager 实现，该实现基于其名称自动合并持久化单元，如下例所示：
Spring supports having multiple persistence units. Sometimes, however, you might want to modularize your application but still make sure that all these modules run inside a single persistence unit. To enable that behavior, Spring Data JPA offers a PersistenceUnitManager implementation that automatically merges persistence units based on their name, as shown in the following example:
.Using MergingPersistenceUnitmanager
<bean class="….LocalContainerEntityManagerFactoryBean">
<property name="persistenceUnitManager">
<bean class="….MergingPersistenceUnitManager" />
</property>
</bean>Classpath Scanning for @Entity Classes and JPA Mapping Files
纯 JPA 设置要求所有注释映射的实体类都列在 orm.xml 中。同样也适用于 XML 映射文件。Spring Data JPA 提供了一个 ClasspathScanningPersistenceUnitPostProcessor，它获取配置的基本包，并可以选取一个映射文件名模式。然后，它会扫描指定包中注释了 @Entity 或 @MappedSuperclass 的类，加载与文件名模式匹配的配置文件，并将它们交给 JPA 配置。必须如下配置后置处理器：
A plain JPA setup requires all annotation-mapped entity classes to be listed in orm.xml. The same applies to XML mapping files. Spring Data JPA provides a ClasspathScanningPersistenceUnitPostProcessor that gets a base package configured and optionally takes a mapping filename pattern. It then scans the given package for classes annotated with @Entity or @MappedSuperclass, loads the configuration files that match the filename pattern, and hands them to the JPA configuration. The post-processor must be configured as follows:
<bean class="….LocalContainerEntityManagerFactoryBean">
<property name="persistenceUnitPostProcessors">
<list>
<bean class="org.springframework.data.jpa.support.ClasspathScanningPersistenceUnitPostProcessor">
<constructor-arg value="com.acme.domain" />
<property name="mappingFileNamePattern" value="**/*Mapping.xml" />
</bean>
</list>
</property>
</bean>|
从 Spring 3.1 开始，可以在 |
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As of Spring 3.1, a package to scan can be configured on the |