Is `` Required in `persistence.xml` for Entity Management?

Is Required in persistence.xml?

In a standard persistence.xml file, elements are necessary to specify managed persistence classes. Without them, the application cannot recognize entities, even with @Entity annotations present.

Automatic Class Scanning

However, the Java EE specification 5 includes a jar-file element within persistence.xml that can be used for automatic scanning of persistence classes:

<persistence>
  <persistence-unit name="UnitName">
    <jar-file>MyJarFile.jar</jar-file>
    <class>com.example.EntityClass</class>
  </persistence-unit>
</persistence>

Hibernate Auto-Detection

If a spec-compliant approach is not preferred, Hibernate supports auto-detection in Java SE environments:

<persistence-unit name="UnitName">
  <properties>
    <property name="hibernate.archive.autodetection" value="class, hbm" />
    ...
  </properties>
</persistence-unit>

This property scans for annotated classes and Hibernate mapping XML files to automatically discover entities.

Note: For Hibernate versions prior to 5.1, this requires adding the Hibernate EntityManager Bean 2 module as a dependency.

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