A PowerBuilder application can act as a client to an EJB 1.1 or 2.0 component running on an application server that is J2EE compliant. This capability relies on PowerBuilder extension files provided by Sybase.
PowerBuilder extension files are developed using the PowerBuilder Native Interface (PBNI). You do not need to know anything about PBNI to create EJB clients, but you can read more about PowerBuilder extensions in the PowerBuilder Extension Reference, and about PBNI in the PowerBuilder Native Interface Programmers Guide and Reference.
EJB clients for EAServer
If you are developing EJB clients for EAServer,
you can use the techniques described in this chapter, or you can
create a client that uses the PowerBuilder Connection object and EAServer proxy objects.
The EJB client extension is a wrapper for Java, and therefore provides more flexibility in communicating with EJBs. For example, an EJB client can manipulate a Java class returned from an EJB method call through its proxy.
The PowerBuilder Connection object has a smaller footprint (and thus is easier to deploy) because it does not require a JRE to be installed on the computer where the client resides. Connectivity to the server is also faster with the connection object, because there is no delay while a JRE loads.
For more information about building an EJB client for an EJB component running on EAServer using the PowerBuilder connection object, see Chapter 24, “Building an EAServer Client.”
To connect to the server and communicate with the EJB component, clients use a set of classes implemented in a DLL file with the suffix PBX, pbejbclient125.pbx. To use the classes in this PBX file, you must import the definitions in it into a library in the client application. You can also add the pbejbclient125.pbd file, which acts as a wrapper for the PBX file, to the target’s library search path.
The PowerBuilder client uses local proxy objects for the EJB component to delegate calls to methods on the remote EJB component. At a minimum, each EJB component is represented in the client application by a proxy for the home interface and a proxy for the remote interface. For example, an EJB component named Cart has two proxies, CartHome and Cart, each containing only the signatures of the public methods of those interfaces.
Additional proxies are also generated for exceptions and ancillary classes used by the home and remote interfaces. For more information, see “Generating EJB proxy objects”.
To build an EJB client, you need to complete the following steps:
Create a workspace and a PowerScript target.
Add pbejbclient125.pbx to the application.
Create a project for building proxy objects.
Build the project to generate the proxy objects.
Create the windows required to implement the user interface of the client application.
Instantiate a Java VM.
Establish a connection to the server and look up the EJB.
Create an instance of the EJB component and call component methods from the client.
Test and debug the client.
