Modeling Apps with Sun Java Studio

In the last issue (Sun Java Studio 8 Enterprise Edition,

page 59, February 2006), we designed three simple classes for our sample library

management software. To that project, we will now add an interface, add

implementation of the interface to an existing class, and also create a simple

activity diagram using Java Studio.

Creating interfaces



To create an interface, click on the Interface icon from the



'Modeling Palette' and click on the diagram. Right click to switch to the

normal cursor. Rename the Interface by typing the name

'LibraryManagerInterface' and keeping the icon selected. Add the following

operations to the interface.

public boolean

checkStatus(int bookId)



public boolean checkMember(int memberId)







public int computeFine(int noOfDays)

The procedure for adding an operation to an interface is

similar to that for a class. Add operations for checkStatus, checkMember and

comptueFine by right-clicking in the Operations section of the Interface and

choosing 'Insert Operation' from the context menu.

Packaging



To model packages, repeat the steps we used for creating interfaces on the

Modeling palette. Rename the package to 'libpack'. To add the classes to

this package, click on the 'Nested Link' icon on the basic section of the

'Modeling Palette'. Click on a class and then on the package. Repeat for all

the classes and interfaces to group them into one package.

Methods from the 'LibraryManagerInterface' automatically appear in the Librarian class after modeling implementation relationship

Complete UML class diagram for the sample application shows all the relationships between classes

The workflow process of issuing a book is represented by an activity diagram as shown here

Relationships



Our interface is implemented by the Librarian class. To model this

relationship, on the Modeling palette select



Implementation>Librarian, and then click on the interface. A new section

appears in the Librarian class titled 'Operations Redefined from

LibraryManagerInterface' listing all the three operations we had created in

our interface. Right click on the Librarian class and click on 'Navigate to

Source Code' from the menu. The Librarian class will open up showing the

changes you had earlier modeled in the UML project. The Library class uses

Member and Book classes as parameters in its methods. This relationship is

represented as dependency in the Studio. To model it, click on the Dependency

icon in the Modeling Palette, click within the Librarian class icon, and then on

Member to model the relationship between the two. Similarly you can model the

relationship between Librarian and Book.

Activity diagram



Activity diagrams essentially help in modeling a business process. Here, we

will model the process for issuing a book. Right click on Model under

'LibraryUML' in the Project Explorer window, and choose Add from the menu

and click on



Diagram in the sub menu that  appears. Choose 'Activity Diagram' from

the 'New Wizard' window. Populate name field with 'Issue Book Activity'

and leave namespace to the default value, which will be LibraryUML in this case.

The IDE opens up an empty diagram window with a different

set of icons in the Modeling Palette. Click on the 'Initial Node' icon from

the palette and then click on the empty diagram. The Initial Node represents the

start of an activity (for example,  Invocation,

Decision) represent the subsequent steps. Click on the Invocation node and place

it in the diagram, right click and rename the node to 'Request for Book'.

Similarly, draw two more Invocation nodes titled 'Search Book' and 'Issue

Book'. Once 'Search Book'



action completes, we need to check for availability, and then issue it. To model

this flow, click on the Decision node and draw it in the diagram. Rename it to

'Check Availability'. Similarly, draw another Decision node and name it

'Issue Another Book'. To connect the activities, click on 'Activity

Edge', followed by clicking on the Initial node in the diagram, and then by

clicking on 'Request for Book'.

Connect 'Request for Book' to 'Search Book' and

'Search Book to Check Availability'. The 'Check Availability' node then

needs to be connected to 'Issue Another Book' and the 'Issue Book'

nodes,  depending on whether the book is available. This draws an activity

edge from 'Check Availability' to 'Issue Book'. To draw another activity

edge from 'Check Availability', from the Properties window and change the

name to Else. Connect the 'Issue Another Book'

Decision node to 'Request for Book'. Click on

'Activity Final' node icon from the palette, place it on the diagram and

connect 'Issue Book' to this node. Finally, connect the 'Issue Another

Book'

Decision node to the 'Activity Final' node and rename

it to Else. This completes our Activity Diagram for 'Issuing Book'.

Modeling can also be done for state transitions, components

and collaboration in an application using the IDE. It is always good to finalize

on these features before you get down to coding to get a well defined platform

on the basis of which all the methods,



interfaces and protocols between objects can be implemented.

Anadi Misra