The application presentation layer works in conjunction with a system application
server (such as IBM® WebSphere® Application
Server) to provide a layered multiple channel architecture. The application
presentation layer works as a bridge that connects the clients with the application
logic layer, which performs business transactions. Java™ clients and HTML clients use different
application presentation components to connect to the application logic layer.
To get connected with the application logic layer, the presentation layer
defines the following entities:
- Java RequestHandler processes a Java client request
for a particular type of requester. The toolkit registers these handlers to
determine which specific handler it needs for a specific request. For example,
there are different RequestHandlers for requests coming from a Java client
in a home banking environment, from a Java client in a branch teller environment,
and from a Java client in a call center environment. The RequestHandler is
responsible for interacting with the client side operations that controls
the dialog navigation for a specific client type and for interacting with
invokers that call application logic layer transactions.
- Java PresentationHandler processes the reply for a particular
type of requester.
- Web2.0 RequestHandler is responsible for processing a particular request from Web 2.0 client.
The request handler performs the following tasks to integrate with the application:
- Executes a generic application operation for the Web 2.0 channel
- Determines the appropriate presentation handler from the handler registry to render the results back to the client.
- Web2.0 PresentationHandler is responsible for processing the reply to the Web 2.0 client.
- JSF RequestHandler processes requests from HTML clients,
calls application logic layer components for business transactions, and renders presentation
for HTML clients based on the business transaction results.
- HTML RequestHandler is responsible for processing a particular
request from an HTML client. The handler may need to be aware of the device
type. This is managed by the channel context. The request handler performs
the following tasks to integrate with the application:
- Establishes the session between the client and the server for the specific
device
- Executes a generic application operation for the HTML channel
- Determines the appropriate presentation handler from the handler registry
to render the results back to the client.
- HTML PresentationHandler is responsible for processing the reply
to the HTML client. The main API provided by this class is void processReply(ChannelContext,
ServerOperation). This starts the process of dynamically creating
the HTML and rendering it to the client using the servlet JSP engine.
To pass business process requests to the application logic layer, the application
presentation layer has the Bean Invoker Factory. The Bean Invoker Factory
creates invokers so that the requester can invoke the EJBs that perform the
business processes in the application logic layer. The requester can be a
request handler from the Java client or an EJB Action from the toolkit Struts
Extensions component.