In this chapter we covered how to take advantage of EJB 2.0 relationships and inheritance to introduce realistic dependencies among the EJBs within your object model. We provided detailed information of how EJB relationship and inheritance is created as well as how it is implemented. You have seen how the top-down and bottom-up mapping strategies support these dependencies. We also covered detailed information of how to use meet-in-the-middle mapping to map both EJB relationships and inheritance when the domain model and database are maintained independently.
Finally, we expanded on the introduction of EJB QL from the previous chapter with further details on the EJB QL statement constructs including the SELECT clause, FROM clause, and WHERE clause. We also provided several examples of EJB QL based on our case study which you can use as patterns for your own queries.