CSE 190: Internet ECommerce

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CSE 190 Internet E-Commerce

• Lecture 8

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Application Tier Architecture

• Model View Controller pattern
• Model 2 architecture
• Statelessness of application tier
• Interaction with data tier
• Interaction with presentation tier
• Validation components

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Model View Controller (MVC)

• MVC Design used when you have many different
  views of the same data
• Model The entity that represents some object
• View A visualization of that entity
• Controller A set of functions for changing the
  state of a model
• Example Spreadsheet
• Model The spreadsheet table
• View A chart created from the data
• Controller The user interface that allows you to
  change the data in the table

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Model 1 Simple JSP pages with helper classes

• The JSP page serves content by accessing an
  object exposed by the Java Bean (a simple class)

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Model 2 Architecture MVC applied to the
application tier

• A single servlet controls all the requests coming
  in to the site.
• Controller functions
• Validate input
• Change model state
• Forward to the view
• View
• JSP simply renders the resulting page read only
  operations

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Application Tier Stateless

• Application tier designed to be stateless
• Allows any app server to fail, and we can replace
  it with an identical server
• Any state that is kept in the app server should
  be cache state (typically read-only)

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App Tier Talks to Data Tier

• Class ShoppingCart
• EntityShoppingCart _cart
• ShoppingCart( int userId )
• _cart EntityShoppingCart(userId)
• String getDescription( int itemNum )
• return _cart.getItem( itemNum
  ).getDescription()
• .

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Presentation Tier Talks to App Tier

• Should never need to execute code more complex
  than a simple method call within presentation
  tier
• ltulgt
• ltligtlt cart.getDescription() gt

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Validation components

• Servlet controller Usually two parts
• Validator
• Command object
• First, parsed input from forms is passed to a
  form validator object
• On failure, forward to error page
• Then apply designed command object
• Finally, forward to view page

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Exam

• (2 pts) Explain the purpose of each tier of a web
  service. Draw a diagram illustrating the
  components of each tier. Briefly note the purpose
  of each component.

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Exam

• 2. (2 pts) Write the URL that represents a
  request to the machine www.yourbusiness.com
  getting document /cgi-bin/render with two
  arguments address1 with value 9500 Gilman
  Drive, address2 with value La Jolla, CA 92093.
  (Quotes are not part of the value.)

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Exam

• 3. (3 pts) Write the HTML for a form that will
  collect this input from the user and allow them
  to submit it to the URL above.

13
Exam

• 4. (3 pts) Explain why you might use a
  stylesheet to position HTML elements rather than
  a borderless HTML table acting as a container.
  Write an HTML file with an internal stylesheet
  that applies an italic font-style and 24pt
  font-size to all H1 and H2 elements on the page.

14
Exam

• 5. (2 pts) Write an HTML page that uses
  Javascript to write the current date at the end
  of the document, using the built in Date()
  function.

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Exam 1

• 6. (2 pts) Write the Javascript code to display
  the innerHTML of the first form of an HTML page.

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Exam

• 7. (3 pts) Show the complete request and
  response issued when an HTTP/1.0 client requests
  the HTML document /index.asp from the HTTP/1.1
  server at www.hotdog.com. Indicate when the
  connection closes.

17
Exam

• 8. (3 pts) Explain the relationship between
  parent and children processes in Apache. What is
  the rationale for this relationship?

18
Exam

• 9. Bonus (2 pts) Given the settings below in
  httpd.conf, what is the exact pathname of the
  file retrieved by http//mysite.com8080/user/ski/
  home.asp ?
• NameVirtualHost
• ltVirtualHost gt
• ServerAdmin sinala_at_gremlin.ucsd.edu
• DocumentRoot "/home/sinala/apache/htdocs"
• ServerName gremlin.ucsd.edu
• ErrorLog logs/error_log
• CustomLog logs/access_log common
• lt/VirtualHostgt
• ltVirtualHost gt
• ServerAdmin webmaster_at_mysite.com
• DocumentRoot "/home/sinala/apache/htdocs/mysit
  e"
• Port 8080
• ServerName mysite.com
• ErrorLog logs/mysite-error_log
• CustomLog logs/mysite-access_log common
• lt/VirtualHostgt