Unknown primary-key class

When writing an entity bean, the minimum requirements usually include a primary-key class. However, in some cases we might choose not to specify the primary-key class for an entity bean with container-managed persistence (CMP).

Perhaps there is no obvious primary key, or we want to allow the deployer to select the primary key fields at deployment time. The primary key type is usually derived from the type used by the database system that stores the entity objects, and we might not know what this key is.

So, the unknown key type is actually a type chosen at deployment time, making it changeable each time the bean is deployed. Your client code must deal with this key as type Object.

Currently, WebSphere Application Server supports top-down mapping and enables the deployer to choose String keys generated at the application server.

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