Enterprise JavaBeans, Second Edition

Using Enterprise Beans

Now that you actually have a bean to work with, let’s look at how a client would work with a bean to do something useful. We’ll start with the Cabin bean that was defined earlier. A cabin is a thing or place whose description is stored in a database. To make the example a little bit more real, imagine that there are other entity beans, including a Ship, Cruise, Ticket, Passenger, Employee, and so on.

Getting Information from an Entity Bean

Imagine that a GUI client needs to display information about a particular cruise, including the cruise name, the ship name, and a list of cabins. Using the cruise ID obtained from a text field, we can use some of our beans to populate the GUI with data about the requested cruise. Here’s what the code would look like:

CruiseHome cruiseHome = ... getCruiseHome(); // Get the cruise id from a text field. String cruiseID = textFields1.getText(); // Create an EJB primary key from the cruise id. CruisePrimaryKey pk = new CruisePrimaryKey(cruiseID); // Use the primary key to find the cruise. Cruise cruise = cruiseHome.findByPrimaryKey(pk); // Set text field 2 to show the cruise name. textField2.setText(cruise.getName()); // Get a remote reference to the ship that will be used // for the cruise from the cruise bean. Ship ship = cruise.getShip(); // Set text field 3 to show the ship's name. textField3.setText(ship.getName()); // Get a list of all the cabins on the ship as remote references // to the cabin beans. Cabin [] cabins = ...