Using an exposed domain model - POJOs in Action: Developing Enterprise Applications with Lightweight Frameworks - page 306

chooses based on the outcome of calling PlaceOrderService . A JSP page generates
the response using the domain objects passed to them by the servlets.
Persistence framework connections are managed by Spring's OpenSessionIn-
ViewFilter and OpenPersistenceManagerInViewFilter classes. Transactions are
managed by Spring's TransactionInterceptor , which uses a persistence frame-
work-specific PlatformTransactionManager that invokes the persistence frame-
work's transaction management API s. The Hibernate version uses the
HibernateTransactionManager , which calls the Hibernate Transaction API , and the
JDO version uses JdoTransactionManager , which calls the JDO Transaction API .
TransactionRetryInterceptor is a custom interceptor that automatically retries a
transaction that was rolled back because of a database concurrency failure and is
described in chapter 12.
In the rest of this section, let's look at the servlets, the JSP pages, and the con-
figuration of the PlaceOrderService Spring bean, which are the same regardless
of which persistence framework is used. After that, in the following sections we
describe the persistence framework-specific parts of the design.

8.4.1 Servlet design

The servlets handle HTTP requests from the user's browser, invoke the business
logic, and forward requests to a JSP page, which generates the response. To see how
these servlets work, let's look at UpdateDeliveryInfoServlet , which handles the sub-
mission of the delivery information form. Listing 8.1 shows the source code for
UpdateDeliveryInfoServlet . The servlet gets the PlaceOrderService from the
Spring WebApplicationContext , a Spring bean factory for the web application.
WebApplicationContext instantiates PlaceOrderService , injects any dependencies,
and wraps it with the AOP interceptors that manage transactions. The servlet obtains
a RestaurantRepository from the WebApplicationContext . The servlet calls Place-
OrderService and RestaurantRepository and forwards the request to a JSP page.

Listing 8.1 UpdateDeliveryInfoServlet

public class UpdateDeliveryInfoServlet extends HttpServlet {

private ServletConfig servletConfig;
private PlaceOrderService service;
bb private RestaurantRepository restaurantRepository;
public void init(ServletConfig servletConfig)
throws ServletException {
super.init(servletConfig);
this.servletConfig = servletConfig;