CCF-to-J2C Architecture Migration

Chapter 7. Migrating a real-life application 83

Figure 7-1 NOVA: the main screen

7.1.2 Model assessment

The model assessment describes an application using different models that

hides the implementation detail of the application. The models give a more

generic and broader view of the application, the way it is divided into

components, and the way they interact with each other and their surroundings.

The assessment is split in two: the architecture and the component model.

Application architecture

Figure 7-2 on page 84 shows the application architectural model. The application

is deployed to a WebSphere Application Server hosted on z/OS. This is a Version

4.0.x in Version 3.5 configuration.

Conceptually, the application is simple and includes Java, CICS, DB2, and not

much else. The complexity of the application is in the number of features, the

complexity of the interfaces, and the fault tolerance and management of the

application.

84 CCF-to-J2C Architecture Migration

Figure 7-2 Architecture diagram

The Web part is developed using an IBM Web application framework originally

named Jade, but renamed to Enterprise Application Development framework for

Java (EAD4J).

Application components

Figure 7-3 on page 85 shows a simplified component diagram for the application.

Some components have been omitted for simplicity, including ResultBeans, JSP,

and other parts of the application that are not responsible for the instantiation of

objects that interact with CCF classes.

Chapter 7. Migrating a real-life application 85

Figure 7-3 Component diagram

The responsibilities of the different components are:

򐂰

BaseServlet is the super class of the two servlets used in the application

(NovaLaunch and NovaControl). The servlet responsibilities are:

– Responsible for the interaction with the user’s Web browser. Transforms

the Web browser request into a command and initiates the execution of

the command.

– When the command has been executed, the result is transferred to the

JSP used to display the result.

– Manages the execution of the JSP used for the display of the result.

– The top level Error handling. If an error occurs that inhibits the completion

of the processing, an error page displays the error to the user.

86 CCF-to-J2C Architecture Migration

򐂰 CommandAdapter is the interface for the commands instantiated and

executed by the Servlet. The implemented classes are responsible for:

– Validation of the input parameters transferred from the request

– Calling the correct NovaBusinessProcess class for the Service requested

– Transferring the result of the NovaBusinessProcess to a resultBean

– Setting the name of the JSP to use to display the result of the request

򐂰

NovaBusinessProcess classes are singletons that contains methods for

various business logic in the application. Several NovaBusinessProcess

classes group the different sets of business logic. Their responsibilities are:

– Instantiate or retrieve the business objects necessary for the request.

– Instantiate one or more CTGCommand classes to perform the request.

– Provide the outcome in business model objects ready for inclusion into the

ResultBean.

򐂰 The

CTGCommand classes are the classes that interact directly with CCF

classes. Their responsibilities are:

– Create a CICS transaction request from the business model objects

provided by the NovaBusinessProcess.

– Request the transaction through the NovaGateway.

– Transform the CICS transaction reply into the business model objects to

be used by the NovaBusinessProcess.

– Create the ECIRequest object from the byte array from the CCF classes.

The ECIRequest object contains the transaction ID and execution mode.

The CICS TG classes can be chained; for example, the

OrderReadCTGCommand class contains calls to the

OrderLineReadCTGCommand to enable the full load of an order from within

one CTGCommand class.

򐂰 The

NovaRecord classes and the NovaRecordType classes are the

CCF-generated classes. They are responsible for transforming a CICS

transaction format (a byte array) into a Java object and vice versa.

򐂰 The

NovaGateway class is a singleton. Its responsibilities are:

– Create a single instance of the CTG JavaGateway class with specific

parameters for the connection.

– Manage errors and faults in the interface and enable the ability to

reconnect to CICS after a communications error has occurred.

򐂰 The

CTG JavaGateway provided by the CICS Transaction Gateway product is

responsible for direct communication with CICS.

Chapter 7. Migrating a real-life application 87

Interaction diagrams

The next two diagrams show the simplified interaction of the components in the

application.

The first diagram (Figure 7-4) displays the interaction from the Web browser

through the servlet and command layers to the business process component.

None of these components has interactions with classes generated from CCF.

Figure 7-4 Interaction diagram for the components not interacting with CCF classes

The second diagram (Figure 7-5 on page 88) displays the interactions of the

components using CCF-generated classes.