How Can I Avoid Manually Specifying Entities in persistence.xml?

Scan for Entities in Persistence.xml File

Introduction

Persistence annotations enable automatic entity discovery in JPA. However, manually specifying entity classes in persistence.xml provides additional control. But what if you want to avoid this manual step?

Automatic Scanning Mechanism

JPA does not provide an automatic scanning mechanism. If you omit the elements in persistence.xml, JPA will not recognize your annotated entities.

Using JAR Files

For Java EE:

allows you to specify a JAR file containing your entity classes:

<jar-file>MyOrderApp.jar</jar-file>
<class>com.widgets.Order</class>

For Java SE with Hibernate:

Hibernate supports auto-detection in Java SE through the hibernate.archive.autodetection property:

<persistence-unit name="eventractor" transaction-type="RESOURCE_LOCAL">
  <properties>
    <property name="hibernate.archive.autodetection" value="class, hbm"/> <!-- Scan for annotated classes and Hibernate mapping XML files -->
  </properties>
</persistence-unit>

Conclusion

While specifying elements in persistence.xml is recommended for Java EE compliance, Hibernate provides a convenient auto-detection feature in Java SE. This eliminates the need for manual entity enumeration, simplifying your JPA configuration.

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