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javajpaeclipselinkjpa-2.0

JPA entity mapping to optional SecondaryTable

I have an entity. I would like to optionally load additional information about the entity from a secondary table. I have the following mapping.

@Entity
@Table( name = "program", schema = "myschema" )
@SecondaryTable( name = "program_info", schema = "myschema", pkJoinColumns =
        @PrimaryKeyJoinColumn( name = "program_id", referencedColumnName = "program_id" ) )
public class Program { ... }

I have all the columns mapped appropriately, and a unit test that works. The trouble comes when I have a row in the program table that does not have a corresponding row in the program_info table. In that case it won't load the program at all. I need to be able to mark the entire secondary table as optional. I would prefer to stay away from having to create another entity/dao/service and do a 1-1 mapping.

I'm using eclipselink but would like to stay away from provider specific details if I can.

Solution

  • I need to be able to mark the entire secondary table as optional.

    EclipseLink will perform an INNER JOIN with a SecondaryTable so if there is no corresponding row in the secondary table, you'll get nothing. In other words EL expects to find a row in the secondary table (when creating, reading, updating, deleting).

    If what you want is an OUTER JOIN, you should use an optional OneToOne association (maybe with a shared primary key in your case).

    An alternative would be to use a database view (doing an OUTER JOIN) and to map the view.

    I would prefer to stay away from having to create another entity/dao/service and do a 1-1 mapping.

    I don't see why having an optional OneToOne forces you to have a corresponding DAO and service. Manage the optional part through the main "holder" part.

    See also