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J2EE Web Fundamentals Lesson 4 Request and Response

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

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  1. J2EE Web FundamentalsLesson 4Request and Response Instructor: Dr. Segun Adekile

  2. 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

  3. Objectives

  4. Agenda • How the Container Handles a Request • Servlet Lifecycle • Loading • Initialization • Service • HTTP Methods • Request Object • Response Object • Response Redirect • Request Dispatch

  5. How the Container Handles a Request

  6. How the Container Handles a Request

  7. How the Container Handles a Request

  8. 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

  9. Servlet Lifecycle

  10. Servlet Lifecycle

  11. Servlet Lifecycle

  12. 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.

  13. 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.

  14. Servlet Initialization

  15. Servlet Service: Request and Response

  16. Servlet Service - HTTP Methods

  17. Servlet Service - HTTP Methods • Intended use: • for getting things • Idempotent • Intended use: • for sending data to be processed • Non-idempotent

  18. Servlet Service - HTTP Methods

  19. Sending and using a single parameter getParameterValues – for multiple values

  20. Servlet Service – Request Object

  21. Lifecycle key points

  22. HTTPServletRequest key points

  23. 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.

  24. Response Redirect

  25. Response Redirect

  26. Request Dispatch

  27. HTTPServletResponsekey points

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