Case Study + MVC

Lec - 39

Error Pages

Error Pages

• By means of the page directive, a JSP can be given the responsibility of an Error page

• An Error JSP will be called by the Web Server when an uncaught exception gets generated

• The exception is passed as an instance of java.lang.Throwable to the Error JSP (accessible via implicit exception object)

Defining & UsingError Pages

• isErrorPage attribute of page directive is used to declare a JSP as an error page.

• JSP pages are informed about the error page by setting errorPage attribute of page directive.

Example Case StudyAddress Book

using Model-1 architecture

Address Bookingredients

• Database

Address Bookingredients

• JavaBeans– PersonInfo

• Has attributes– name– address– phoneNum

– PersonDAO• Encapsulate Database logic• Used to retrieve & save PersonInfo data

Address Bookingredients

• JavaServer Pages– addperson.jsp

• Used to collect new person info

– saveperson.jsp• Receives person info from addperson.jsp• Saves it into database

– searchperson.jsp • Used to provide search criteria to search Person’s info, based

on name

– showperson.jsp• Receives person name, to be searched in database• Retrieves & display person records against that person name

Address Book ingredients

• JavaServer Pages (cont.)

– Error Pages

• addbookerror.jsp

– Identifies the type of exception

– Displays the message associated with the received exception

Program Flow

addperson.jsp

saveperson.jsp

showperson.jsp

PersonInfo

PersonDAOJavaBeans

uses

uses

addbookerror.jspexception

searchperson.jsp

Lets put it all together

Netbeans project addressbookusingmodel1

Model View Controller Design Pattern

Model-View-ControllerDesign Pattern

• MVC separates

– Application data (contained in the model) from

– Graphical presentation components (the view) &

– Input/Event processing logic (the controller)

MVC in general

modelview

controller

MVC in general: model

modelview

controller

• Represents the state of the component (ie its data and the methods required to manipulate it)

• Independent of how the component is viewed or rendered

MVC in general: view

modelview

controller• Appearance of the

component

• Can be multiple views for the same model within a single applications

• Model may have different views in different applications or operating systems

MVC in general: controller

modelview

controller

• Dictates how a component interacts with events

• Sends events of interest to the model so that it can update itself

MVC in summary

Evolution of MVC Architecture

• No MVC

2. MVC Model 1

3. MVC Model 2

4. Web application framework (based on MVC model2)– Struts, Sun ONE application framework

5. Web application framework– JavaServer Faces (JSF)

MVC Model 1Architecture

MVC Model 1

MVC Model 1 – A Detailed Story

ClientClient

JSP Engine & Web Server

JSP Engine & Web Server

request

JSPFileJSPFile

request

request Call for component

Component(JavaBean or EJB)

Component(JavaBean or EJB)

responseData

response

response

CompiledServlet

MVC Model 2

Bean

JSP

JSP /Servlet

Controller

View

Model