1. SOEN 343 Software Design
Computer Science and Software Engineering Department
Concordia University
Fall 2005
Instructor: Patrice Chalin

2. Agenda – Lecture 10a Review & renew. Controller Patterns
GRASP
EA: Page and Front Controllers.
A Spectrum of Web EA alternate designs.
12/1/2018
SOEN 343, © P.Chalin,

3. GRASP: Controller Who handles a system event?
E.g. “List Movies”
Main choices: assign to a design entity representing
Overall system, or subsystem (façade controller).
A Use Case scenario (often named, e.g. ListMovieHandler).
12/1/2018
SOEN 343, © P.Chalin,

4. GRASP: Controller Who handles a system event?
E.g. “List Movies”
Main choices: assign to a design entity representing
Overall system, or subsystem (façade controller).
A Use Case scenario (often named, e.g. ListMovieHandler).
12/1/2018
SOEN 343, © P.Chalin,

5. Presentation Domain Data Source Controller Patterns Page Controller
Template View
Presentation
Front Controller
Transform View
Domain Model
Transaction Script
Domain
Data Mapper
Active Record
Table Module
Data Mapper
Row Data Gateway
Table Data Gateway
Data Source
Table Data Gateway
12/1/2018
SOEN 343, © P.Chalin,

6. Page Controller
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SOEN 343, © P.Chalin,

7. A1 Page Controllers protected void processRequest(
HttpServletResponse response)
throws ServletException, java.io.IOException // {
TaskListHelper helper = new TaskListHelper();
try {
ViewTaskListTS.execute(helper);
} catch (Exception e) {
helper.appendStatus(e.toString()); }
if (helper.getTaskList() == null) {
request.setAttribute("errorMessage", helper.getStatus());
forward("Error.jsp", request, response);
} else {
request.setAttribute("helper", helper);
forward("TaskManager.jsp", request, response);
12/1/2018
SOEN 343, © P.Chalin,

8. A1 Page Controllers protected void processRequest(…) throws … {
TaskListHelper helper = new TaskListHelper();
try {
ViewTaskListTS.execute(helper);
} catch (Exception e) {
helper.appendStatus(e.toString()); }
if (helper.getTaskList() == null) {
request.setAttribute("errorMessage", helper.getStatus());
forward("Error.jsp", request, response);
} else {
request.setAttribute("helper", helper);
forward("TaskManager.jsp", request, response);
12/1/2018
SOEN 343, © P.Chalin,

9. Page Controller vs. Front Controller – Differences in URL
12/1/2018
SOEN 343, © P.Chalin,

10. Page Controllers for A1 http:/stu.cs/343A1/ViewTaskList …
12/1/2018
SOEN 343, © P.Chalin,

11. Front Controller for A1 Base URL: http:/stu.cs/343A1/frontController
…/frontController ?command=ViewTaskList
…/frontController ?command=AddTaskGrade&title=abc&…
12/1/2018
SOEN 343, © P.Chalin,

12. Front Controller
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SOEN 343, © P.Chalin,

13. Front Controller
12/1/2018
SOEN 343, © P.Chalin,

14. Front Controller (Fowler) Command (GoF) Patterns
FrontCommand
+ init ( )
+ processRequest ( )
RemoveStudentCommand
ViewStudInfoCommand
+ processRequest ( )
+ processRequest ( )
12/1/2018
SOEN 343, © P.Chalin,

15. Front Controller: Sequence Diagram
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SOEN 343, © P.Chalin,

16. Front Controller: ProcessRequest
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SOEN 343, © P.Chalin,

17. Front Controller (cont’d)
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SOEN 343, © P.Chalin,

18. Front Controller: Advantages?
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SOEN 343, © P.Chalin,

19. Web EA Redesign Exercise
Refactoring a DoItAll Servlet, let me count the ways …
12/1/2018
SOEN 343, © P.Chalin,

20. Do-it-all Servlet or Script
Presentation
Do-it-all Servlet or Script
Domain
Data Source
12/1/2018
SOEN 343, © P.Chalin,

21. Do-it-all Servlet or Script, Class
public class DoItAll extends javax.servlet.http.HttpServlet {
protected void doGet(
HttpServletRequest request,
HttpServletResponse response)
throws ... // … }
12/1/2018
SOEN 343, © P.Chalin,

22. Redesigning This Application
Redesign DoItAll so as to increase the class cohesion.
Create new classes. Which EA patterns would you use?
Distribute the doGet() method code (given on the next slide) into the new classes. Identify which lines would go into which classes.
12/1/2018
SOEN 343, © P.Chalin,

23. Do-it-all Transaction Script, doGet()
String lastName = request.getParameter(“…");
Connection dbc = DbRegistry.getDbConnection();
String findSql = "SELECT * from … where LastName = ?”;
PreparedStatement dbQuery = dbc.prepareStatement(findSql);
dbQuery.setString(1, lastName);
ResultSet rs = dbQuery.executeQuery();
rs.next();
String firstName = rs.getString("FirstName");
lastName = lastName.toUpperCase();
PrintWriter out = response.getWriter();
response.setContentType("text/html");
out.println("<h1>Hello "+firstName+" "+lastName+"</h1>");
12/1/2018
SOEN 343, © P.Chalin,

24. Do-it-all Servlet Redesign: Separating Concerns
The next few slides show ways in which we can separate concerns; i.e. distribute the functionality of the do-it-all script into separate classes.
Combinations other than the ones shown are possible.
12/1/2018
SOEN 343, © P.Chalin,

25. Redesigning Do-it-all (2 classes) [#1]
Presentation
Do-it-all
redesign
Domain
Data Source
Note:
12/1/2018
SOEN 343, © P.Chalin,

26. Redesigning Do-it-all (3 classes) [#3]
Presentation
Do-it-all
redesign
Domain
Data Source
12/1/2018
SOEN 343, © P.Chalin,

27. Redesigning Do-it-all (4 classes) [#4]
Presentation
Do-it-all
redesign
Domain
Data Source
12/1/2018
SOEN 343, © P.Chalin,

28. Redesigning Do-it-all : Adding … (5 classes) [#5]
Presentation
Do-it-all
redesign
Domain
Data Source
12/1/2018
SOEN 343, © P.Chalin,

29. Redesigning Do-it-all : Adding … [#5b]
Presentation
Do-it-all
redesign
Domain
Data Source
12/1/2018
SOEN 343, © P.Chalin,

30. Redesigning Do-it-all (5 classes) [#5c]
Presentation
Do-it-all
redesign
Domain
Data Source
Is there anything wrong with this design? (Hint: consider the dependencies and the layering style.)
12/1/2018
SOEN 343, © P.Chalin,

31. Redesigning Do-it-all (6 classes) [#6]
Presentation
Do-it-all
redesign
Domain
Data Source
12/1/2018
SOEN 343, © P.Chalin,

32. Enterprise Application Patterns (v1.3)
Page Controller
Template View
Presentation
Front Controller
Transform View
Domain Model
Transaction Script
Domain
Data Mapper
Active Record
Table Module
Data Mapper
Row Data Gateway
Table Data Gateway
Data Source
Table Data Gateway
12/1/2018
SOEN 343, © P.Chalin,