With the design in place, your component developers and client developers can begin implementing the clients and components that form the application.
To create an EJB component, use PowerJ or another JDK-1.2 compatible development tool to create the component. From PowerJ you can import the component definitions into EJB Server, and deploy the component on the EJB Server. If using another development tool, you must perform these tasks with the Adaptive Server plug-in.
To learn how to build EJB components, see Chapter 6, “Working with EJB Packages and Components.”
Client developers can work concurrently with component developers. To allow prototyping and testing of client programs, you may want to create a client test server that hosts stubbed versions of the application components (that is, components with minimal method implementations). All clients for EJB Server components must be Java clients.
The Java client Java applets do not require customer installation and simplify the task of providing upgrades. The customer always downloads the most recent applet. If you do not want the customer to wait for the Java classes to download from the EJB Server, you can install the Java classes on the client machine or use Marimba Castanet to speed up the download time.
If the client application is large and requires many Java classes, download time might be unacceptable. In this case, use a Java application that is installed locally on the client machine. This approach is ideal for intranet customers or even regular Internet customers. Although not as simple as providing upgrades with an applet, Java applications are no more difficult to upgrade than conventional software. In fact, Marimba Castanet can be used to automatically upgrade the Java application across the Internet.
Java IDEs such as PowerJ offer visual interface builders that greatly simplify the implementation of the user interface.
In some situations, you might want to implement different versions of a client for different users. For example, you may implement a Java applet version to allow new customers to connect over the Internet without installing a client program. For established customers who use the application heavily, you can implement a standalone client program that offers improved performance.
Client design issues In designing your client, plan to optimize network performance by keeping traffic between the client and components on the server to a minimum. To optimize network performance, plan to:
Cache property changes in client data structures.
Validate field values on the client.
Update only the rows and columns that have changed. For example, do not implement a client to update an entire table when only a few rows have changed.
Group data changes into larger sets with fewer method calls.
