Right way to realize Domain-entity

How correctly realize Domain-entity, which will invoke in servlet? What is saying best practicies? And Martin Fowler recommends?

I give a simple example: For example we have an EJB project, classes StudentDAO and GroupDAO (students and groups).

And we have next example code in the servlet:

@Override
protected void doGet(final HttpServletRequest request, final HttpServletResponse response) throws ServletException, IOException
{
        // Read GET-params
        ...

        // Invoke to business-logic classes
        final List<Group> groups = groupDAO.getAll();
        final List<Student> students = studentDAO.filter(//... different filtering params...);

        // Send request to client, or catch exceptions and send it
        ...
}

So, we direct appeal to DAO entities.

Is next variant is better:

@EJB
GroupDomain groupDomain;

@EJB
StudentDomain studentDomain;

...

final List<Group> groups = groupDomain.getAll();
final List<Student> students = studentDomain.filter(//... ...);

Or the Domain entity should be single? But how to get list of all groups and filtered list of students in this case?