SPRING BOOT WEB MVC

MVC is a design pattern used to implement Web Application.

M=Model(Data/Entity Classes)

V=View(UI/HTML)

C=Controller(Request processing code)

*)Controller supports HTTP Protocol(Request/Response)

1)Project/Application->Modules

2)Gmail App->Idex,User Register/Login etc.

3)BusTicket->User,Search,BookTicket etc.

    1Module=1Controller

Ex:-UserController

    HandlerMapping

    ==============

   Key(Path+Http Method)    Value(Controller)

   --------------------     -------------------         

   /emp/show(GET)      EmployeeController(show data())

   /std/save(POST)      StudentController(save data())

 Execution Flow

 ==============

 #1 Browser makes request to server in 3 different ways.

 a) Enter URL in addressbar[GET](http://facebook.com)

 b) Click Hyper links[GET](<a> tags)(logout,Inbox etc)

 c) HTML form submit[POST](Register,login).

 #2 Request is sent to server.

  HTTP request contains 2 parts.

  Head+Body

 #3 Spring Framework(Web MVC) has provided one pre-defined servlet names as:

  Dispatcher Servlet(c)

  This the only Entry and Exit point.i.e. It will read request and finally it gives response back.

 #4 Front Controller gives Path and method details to HandlerMapping.

 #5 Front Controller(FC) back controller and method details.

 #6 Front Controller will call method by reading object from container like:

   Ex:-empController.showData()

   1 request=1 time method is called

 #7 Controller(is a class) contains request processing code(inside methods) 

   these are executed by FC.

   ->Browser is sending login data,validate it.

   ->Browser is asking for logout.

   ->Browser is asking to post one comment[save data in db and reflect back to UI]

    Controller also provides data(if requireed/i.e option)

    NOTE:-

    -----

    Controller must returns ViewName

    ->Model stores data in key(String)=Val(Object)Format

    Model

    ======

   Key     value

   ----    -------

   UserName  Shailja

   Logintime  12:40 16/2/2021 IST 4:00

 #10 FC reads ViewName and takes help of ViewResolver(class)that provides

 prefix (location od UI pages)and Suffix(extension)

  Prefix=/webpages/myviews/

  Suffix=.html

  ViewPage= Prefix + ViewName + Suffix

 #12 FC finally gets ViewPage details and calls/execute UI page.

 #13 UI reads data from Model memory and replaces all expression with actual data.

 #14 Final UI(View) is given back to FC.

 #15 FC send data as Response back to browser.

 #16 Browser will display UI page.