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== Persistence MetaDataanchor:Persistence_MetaData[]

JDO 1.0 and JDO 2.0 support specification of persistence using XML
MetaData. JDO 2.1 adds on the ability to specify persistence using Java5
annotations.

=== XML MetaDataanchor:XML_MetaData[]

JDO expects any XML MetaData to be specified in a file or files in
particular positions in the file system. For example, if you have a
class _com.mycompany.sample.MyExample_, JDO will look for any of the
following files until it finds one (in the order stated) :

....
META-INF/package.jdo
WEB-INF/package.jdo
package.jdo
com/package.jdo
com/mycompany/package.jdo
com/mycompany/sample/package.jdo
com/mycompany/sample/MyExample.jdo
....

In addition to specifying XML MetaData in a *jdo* file, if defining O/R
mapping information you can also split this out into an ORM file. The
locations for ORM files are similar in nature to those for JDO files.

....
META-INF/package-{mapping}.orm
WEB-INF/package-{mapping}.orm
package-{mapping}.orm
com/package-{mapping}.orm
com/mycompany/package-{mapping}.orm
com/mycompany/sample/package-{mapping}.orm
com/mycompany/sample/MyExample-{mapping}.orm
....

where _\{mapping}_ is a property specified by the user and may be
"mysql" for ORM information for MySQL datastores, and "oracle" for ORM
information for Oracle datastores, and so on.

{empty} +


=== Annotationsanchor:Annotations[]

JDO 2.1 provides support for annotations. Classes and fields/properties
can be annotated defining the persistence and, optionally, any ORM
information.