You can use the bottom-up mapping approach to generate CMP enterprise beans and mappings from an existing database schema.
You can use the EJB mapping wizard in the EJB tools and use the following development approaches for mapping enterprise beans to database tables. If you already have entity beans in a project, the mapping gives unique names to generated beans to avoid collision of new table mappings to existing CMP entity beans. By default, relationships are generated where foreign-keys exist.
Backends folder
This product supports multiple backends that make multiple deployments inside a single EJB module configurable at runtime. Bottom-up mapping only supports a single backend. A backend can represent different database vendors, or simply alternative mappings and table qualifiers. If multiple backends exist, then the current BackendID needs to be set in the EJB deployment descriptor editor (when working with EJB 2.x beans). This mapping/deployment will be used at runtime when the JAR is installed on WebSphere® Application Server. When deploying EJB 1.1 beans inside an EJB 2.x project, the EJB 1.1 beans are deployed only once, using the first declared database and type.
To generate enterprise beans and map based on a bottom-up mapping you have the following options: