Database access from session bean
Hello,
I have a stateless session bean which performs some complex
calculations, and also does some database access.
For the database access the bean class has a datasource as
follows:
public class TestBean implements SessionBean {
private DataSource ds_;
public void ejbCreate() {
getDataSources();
...
}
private void getDataSources() {
try {
Context ictx = new InitialContext();
ds_ = (DataSource)ictx.lookup("java:comp/env/jdbc/TestDB");
} catch (Exception e) {
e.printStackTrace();
throw new EJBException(e);
}
}
...
}
Now this class has a method (which is also in the remote interface)
calculateSomething(). This method constructs a number of other
objects that do the actual calculation, and one of these objects
does the actual database access. How would another object be able to
use the datasource that was constructed in the bean class?
I could pass the datasource reference to that object, but that would
break my encapsulation. This is because that object does not get
created directly by the bean object, but rather the way the objects
interact is something like A -> B -> C, where A is the TestBean, and
C is the object that does the DB access. If I passed the datasource,
I would need to make B aware of the datasource, which doesn't
seem good design, because B doesn't do any database access.
Alternatively I could do the lookup in class C, but that would
degrade the performance, as an object C gets created and destroyed
every time the calculateSomething() method is called.
A third option I have thought of, is to add a public method to the
bean that returns a connection. Whenever another object gets
created, a reference to the bean object will be passed along. Then,
if another object needs to do database access, it will call back
the bean to get a connection. This seems just as bad (if not worse)
than the first option.
Does anyone have an elegant solution for this situation? What is
the best practice of handling datasources when a bean class doesn't
do the database access itself? In all the examples I've seen so far,
all the functionality was in the session bean class, but again that
doesn't seem good OO design, and would result in a single huge class.
regards,
Kostas
