Difference between revisions of "EclipseLink/UserGuide/JPA/Basic JPA Development/Configuration/JPA/orm.xml"

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==Advantages and Disadvantages of Using XML==
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Some advantages of using XML instead of [[EclipseLink/UserGuide/JPA/Basic JPA Development/Configuration/JPA/Annotations|Annotations]] include:
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* No coupling between the metadata and the source code
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* Compliance with the existing, pre-EJB 3.0 development process
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* Support in IDEs and source control systems
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The main disadvantages of mapping with XML include:
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*Its inherent complexitiy (when compared to annotations)
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*The need for replication of the code context

Revision as of 14:24, 16 June 2010

orm.xml

Use the orm.xml file to apply the metadata to the persistence unit. This metadata is a union of all the mapping files and the annotations (if there is no xml-mapping-metadata-complete element). If you use one mapping orm.xml file for your metadata and place this file in a META-INF directory on the classpath, then you do not need to explicitly list it. The EclipseLink persistence provider will automatically search for this file (orm.xml)and use it.

If you use a different name for your mapping files, or place them in a different location, you must list them in the mapping-file element of the persistence.xml file, as shown here:

 <persistence-unit name="EmployeeService">
     <jta-data-source>jdbc/EmployeeServiceDS</jta-data-source>
     <mapping-file>META-INF/employee_service_queries.xml</mapping-file>
 </persistence-unit>

Elug note icon.png

Note: In this example, the orm.xml file is not listed -- the persistence provider finds it by default.

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Advantages and Disadvantages of Using XML

Some advantages of using XML instead of Annotations include:

  • No coupling between the metadata and the source code
  • Compliance with the existing, pre-EJB 3.0 development process
  • Support in IDEs and source control systems

The main disadvantages of mapping with XML include:

  • Its inherent complexitiy (when compared to annotations)
  • The need for replication of the code context