In bean-managed persistence, a
primary key
can be a serializable object defined specifically for the bean by the
bean developer. The primary key defines attributes we can use to
locate a specific bean in the database. For the
ShipBean
we need only one attribute,
id
, but in other cases a primary key may have
several attributes, which together uniquely identify a
bean’s data.
We will examine primary keys in detail in Chapter 10; for now, we specify that the Ship EJB uses
a simple single-value primary key of type
java.lang.Integer
. The actual persistence field in
the bean class is an Integer
named
id
.