The document discusses various design patterns in software development, particularly focusing on the Model-View-Controller (MVC), Model-View-Presenter (MVP), Model-View-ViewModel (MVVM), RESTful, and Command Query Responsibility Segregation (CQRS) patterns. It explores the benefits and complexities associated with these patterns, emphasizing the importance of decoupling and flexibility in application design. The content also includes code examples demonstrating each pattern's implementation within different frameworks.

1. JCConf Taiwan 2014
MODERN
DESIGN PATTERN

2. ABOUT ME
王文農a.k.aSteven
Softleader engineer, for build application and framework.
Research interests are adjusted efficiencyand effectiveness of
algorithms.
Playsome of new frameworks/libraries and technology.

3. If you wantto be acoolguy.
JOIN SOFTLEADER.

4. WHAT IS DESIGN PATTERN?

5. Descriptions of communicating objects and
classes thatare customized to solve ageneral
design problem.
–Gamma, et. al

6. THE ONE CONSTANT IN SOFTWARE DEVELOPMENT:
CHANGE!

7. TIGHT COUPLING!

8. IT MIGHT GET YOU INTO TROUBLE

9. BEWARE OF

10. GOF: 23

12. MVC PATTERN

13. A PROBLEM OR A SOLUTION ?
Commonlyreasons:
Reduced Code complexity
Code reuse
Increased flexibility
Decoupled code

14. COOL, SOUNDS NICE, BUT
Is ittrue ?
Do allother patterns lack these coolthings ?

15. THE ANSWER IS NO!
Doesn'tsolve the code complexity problem
Doesn'tsolve the code reuse or no-flexibility problem
Doesn'tguarantee decoupled code

16. MVC COMPONENTS

17. HOW MVC WORKS

21. POOR MVC GIVE BIRTH TO

22. MVC DEMO WITH SERVLET

23. MODEL-VIEW-CONTROLLER

24. MODEL
publicclassModel{
privateStringname;
publicvoidsetName(Stringname){
//businesslogic
this.name=name;
}
//forviewaccess
publicStringgetName(){
returnname;
}
}

25. VIEW
<h1>Hello,${model.name}</h1>
<formaction="controller"method="post">
<labelfor="name">Mynameis</label>
<inputtype="text"id="name"name="name"value="${model.name}"/>
<button>Submit</button>
</form>
<%--receivedata--%>

26. CONTROLLER
@WebServlet(value="/controller")
publicclassControllerextendsHttpServlet{
@Override
protectedvoiddoPost(HttpServletRequestreq,HttpServletResponseresp)throwsServlet
//acceptingrequest
Stringname=req.getParameter("name");
//validaterequest
if(name.isEmpty()){
name="Guest";
}
//useModeltodobusinesslogic
Modelmodel=newModel();
model.setName(name);
//bindingmodeltoview
req.setAttribute("model",model);
//forwardtoview
req.getRequestDispatcher("/v/view.jsp").forward(req,resp);
}
@Override
protectedvoiddoGet(HttpServletRequestreq,HttpServletResponseresp)throwsServletE
//acceptingrequest
//useModeltodobusinesslogic
Modelmodel=newModel();
model.setName("Guest");

27. MVP DEMO WITH VAADIN

28. MODEL-VIEW-PRESENTER

29. MODEL
publicclassModel{
privateStringname;
publicvoidsetName(Stringname){
//businesslogic
this.name=name;
}
//forpresenteraccess
publicStringgetName(){
returnname;
}
}

30. VIEW
publicclassViewextendsCustomComponent{
privateLabeldisplay=newLabel("Hello,Guest");
privateTextFieldname=newTextField("Mynameis");
privateButtonbutton=newButton("Submit");
privatePresenterpresenter;
publicView(){
//initiallayoutandpresenter
initialLayout();
presenter=newPresenter(this);
}
protectedvoidinitialLayout(){
CustomLayoutlayout=newCustomLayout("view");
layout.addComponent(display,"display");
layout.addComponent(name,"name");
button.addClickListener(newClickListener(){
@Override
publicvoidbuttonClick(ClickEventevent){
//whenbuttonclickthendispatchtopresenter
presenter.changeDisplay();
}
});
layout.addComponent(button,"submit");
setCompositionRoot(layout);
}
//viewprovidegetters&setters

31. PRESENTER
publicclassPresenter{
privateViewview;
privateModelmodel;
publicPresenter(Viewview){
this.view=view;
this.model=newModel();
}
publicvoidchangeDisplay(){
Stringname=view.getInput().getValue();
//dosomelogic,eg:validate
if(name.isEmpty()){
name="Guest";
}
//callmodel
model.setName(name);
//controlview
view.setDisplay("Hello,"+model.getName());
}
}

32. MVVM DEMO WITH ZK

33. MODEL-VIEW-VIEWMODEL

34. MODEL
publicclassModel{
privateStringname;
publicvoidsetName(Stringname){
//businesslogic
this.name=name;
}
publicStringgetName(){
returnname;
}
}

35. VIEW
<zk>
<windowtitle="MVVMExample"border="normal"width="100%"
apply="org.zkoss.bind.BindComposer"
viewModel="@id('vm')@init('tw.jcconf.example.mvvm.vm.ViewModel')">
<hbox>
Hello,<labelvalue="@load(vm.model.name)"/>
</hbox>
<hbox>
<labelvalue="Mynameis"/><textboxvalue="@bind(vm.name)"/>
<buttononClick="@command('changeName')"label="Submit"/>
</hbox>
</window>
</zk>

36. VIEWMODEL
publicclassViewModel{
privateStringname;
privateModelmodel;
publicViewModel(){
model=newModel();
model.setName(name="Guest");
}
//eventhandler
@Command
@NotifyChange("model")
publicvoidchangeName()throwsException{
model.setName(name);
}
//ViewModelprovidergetter&setter
publicvoidsetName(Stringname){
this.name=name;
}
publicStringgetName(){
returnname;
}
publicModelgetModel(){
returnmodel;
}
}

37. RESTFUL PATTERN

38. An architectural style thatabstracts the
architectural elements within adistributed
hypermediasystem.
–Wikipedia

39. THE MEAS IS
Use HTTPmethods explicitly.
Be stateless.
Expose directory structure-like URIs.
Transfer XML, JavaScriptObjectNotation
(JSON), or both.
–IBM's developerWorks website

40. WHAT IS REST ?

41. HTTP ITSELF IS REST IMELEMENTATION

42. HOW TO USE ?
User Action HTTP Method
Create POST/PUT
Read (Retrieve) GET
Update (Modify) PUT/PATCH
Delete (Destroy) DELETE

43. LOOK ALIKE
User Action SQL
Create INSERT
Read (Retrieve) SELECT
Update (Modify) UPDATE
Delete (Destroy) DELETE

44. FOLLOW HTTP TO DESIGN RESTFUL WEB SERVICE
Nouns
Define the URL for your resources
Verbs
Choose the rightHTTP method
ContentTypes
Choose content-type which you wantto return

45.
« ‹ › »

46. CREATE
POSThttp://domain/books
{
"isbn":"123456789",
"title":"ModernDesignPattern",
"author":"StevenWang",
"publisher":"JCConfTW",
"year":"2014"
}
HTTP/1.1 200 | 401
{
"id":"9876543"
}

47. READ
GEThttp://domain/books/123456789
or
GEThttp://domain/books?isbn=123456789
HTTP/1.1 200 | 404
[{
"id":"9876543",
"isbn":"123456789",
"title":"ModernDesignPattern",
"author":"StevenWang",
"publisher":"JCConfTW",
"year":"2014"
}]

48. UPDATE
PUThttp://domain/books/9876543
or
PUThttp://domain/books
{
["id":"9876543",]
"isbn":"123456789",,
"title":"ModernDesignPattern",
"author":"StevenWang",
"publisher":"JCConfTW",
"year":"2014"
}
HTTP/1.1 200 | 401 |404

49. DELETE
DELETE http://domain/books/9876543
or
DELETE http://domain/books?isbn=9876543
HTTP/1.1 200 | 401 |404

50. RESTFUL DEMO WITH SPRING

51. @RestController
@RequestMapping("/books")
publicclassBooksResource{
@Autowired
BookServiceservice;
@RequestMapping(consumes="application/json",produces="application/json",method=
@ResponseBody
publicList<Book>getAll(){
returnservice.getAll();
}
@RequestMapping(value="/{isbn}",consumes="application/json",produces="applicat
@ResponseBody
publicBookgetByIsbn(@PathVariable("isbn")Stringisbn){
returnservice.getBookByIsbn(isbn);
}
@RequestMapping(consumes="application/json",produces="application/json",method=
@ResponseBody
publicBooksave(@RequestBodyBookbook){
returnservice.save(book);
}
@RequestMapping(consumes="application/json",produces="application/json",method=
@ResponseBody
publicBookupdate(@RequestBodyBookbook){
returnservice.update(book);
}
@RequestMapping(value="/{id}",consumes="application/json",produces="applicatio
publicvoiddelete(@PathVariable("id")Longid){

52. CQRS PATTERN

53. WHAT IS CQRS ?

54. CQRS is simply the creation of two objects where
there was previously only one. The separation
occurs based upon whether the methods are a
command or aquery (the same definition thatis
used by Meyer in Command and Query
Separation, acommand is any method that
mutates state and aquery is any method that
returns avalue).
–Wikipedia

55. Saywhat?

56. PUT ANOTHER WAY...
Command/QueryResponsibilitySegregation (CQRS) is the idea
thatyou can use adifferentmodelto update information than the
modelyou use to read information.
IN THIS CONTEXT,
Commands = Writes
Queries = Reads

57. OK, BUT WHY ?

58. WHAT IS CQRS NEED ?

60. MULTI-USER SYSTEM

61. TYPICAL APPLICATION OF THE CQRS PATTERN

62. COMMANDS AND EVENTS IN THE CQRS PATTERN

63. WHEN TO AVOID CQRS ?
So, when should you avoid CQRS?
The answer is mostof the time...
–UdiDahan

64. OK, SOME SUGGESTIONS
Large team.
Difficultbusiness logic.
Scalabilitymatters.
Your top people can work on domain logic.

65. FINALLY

66. PATTERNS DON’T SOLVE PROBLEMS,
THEY HELP US