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J2EE Web Fundamentals Lesson 4 Request and Response. Instructor: Dr. Segun Adekile. Outline. Objectives Course Text Book Basham, Bryan; Sierra, Kathy; Bates, Bert (2012-10-30). Head First Servlets and JSP (Kindle Location 1349). O'Reilly Media. Kindle Edition. Request and Response

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J2ee web fundamentals lesson 4 request and response

J2EE Web FundamentalsLesson 4Request and Response

Instructor: Dr. Segun Adekile


Outline
Outline

  • Objectives

  • Course Text Book

    • Basham, Bryan; Sierra, Kathy; Bates, Bert (2012-10-30). Head First Servlets and JSP (Kindle Location 1349). O'Reilly Media. Kindle Edition.

  • Request and Response

    • Being a Servlet



Agenda
Agenda

  • How the Container Handles a Request

  • Servlet Lifecycle

    • Loading

    • Initialization

    • Service

      • HTTP Methods

      • Request Object

      • Response Object

  • Response Redirect

  • Request Dispatch





Servlet lifecycle
Servlet Lifecycle

  • The servlet lifecycle is simple

  • There is only one main state – initialized

  • If the servlet isn’t initialized, then it’s either

    being initialized (running its constructor or

    init() method), being destroyed (running its

    destroy() method), or it simply does not exist





Servlet loading
Servlet Loading

  • When the Container starts, it looks for deployed web apps and then starts searching for servlet class files

    • Findingthe class is the first step

    • Loading the class is the second step, and it happens either on Container startupor first client use. Your Container might give you a choice about class loading, or it might load the class whenever it wants.


Servlet initialization
Servlet Initialization

  • The constructor makes only an object

  • To be a servlet, the object needs to be granted servletness, getting all the unique

    privileges that come with being a servlet e.g. its ServletContextreference.

  • You can override the init() method to add

    operations such as getting a db connection or

    registering yourself with other objects.





Servlet service http methods1
Servlet Service - HTTP Methods

  • Intended use:

  • for getting things

  • Idempotent

  • Intended use:

  • for sending data to be processed

  • Non-idempotent



Sending and using a single parameter
Sending and using a single parameter

getParameterValues – for multiple values




Httpservletrequest key points
HTTPServletRequest key points


Servlet service response object
Servlet Service – Response Object

  • The response is what goes back to the client.

  • It is parsed and rendered by the browser.

  • Typically the response object is used to get an

  • output stream which is used to write the HTML,

    which goes back to the client.






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