5.2. Metadata Placement

5.2. Metadata Placement
Prev	Chapter 5. Metadata	Next

JDO metadata must be available both during class enhancement and at runtime. The metadata document listing a persistence-capable class must be available as a resource from the class' class loader, and must exist in one of two standard locations:

In a resource called class-name.jdo, where class-name is the name of the class the document applies to, without package name. The resource must be located in the same package as the class.
In a resource called package-name.jdo, where package-name is the last token of the package's full name. The resource should be placed in the corresponding package, or in the package's parent package. Package-level documents should contain the metadata for all the persistence-capable classes in the package, except those classes that have individual class-name.jdo resources associated with them.

Assuming you are using a standard Java class loader, these rules imply that for a class Magazine defined by the file org/mag/Magazine.class, the corresponding metadata document could be defined in any of the following files:

org/mag/Magazine.jdo
org/mag/mag.jdo
org/mag.jdo

Because metadata documents are loaded as resources, JDO implementations can also read them from jar files.

	Note
	Some JDO implementations may not support all of the metadata placements discussed, or may support additional placements. Kodo JDO supports the standard metadata locations listed as well as a package-level resource called `package.jdo` and a `system.jdo` resource defining the metadata for the entire system, located in any top-level directory of the `CLASSPATH`.