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Ch5 beeing an application
This document contains notes from a lecture on web technologies. It discusses procedural items like asking some students to speak after class and notifying about assignment grades and deadlines. It also covers technical topics around installing LAMP and Tomcat, using servlets, web application deployment descriptors, context listeners, and ensuring thread safety.
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Ch5 beeing an application
- 1. ΤξĎÎ˝ÎżÎťÎżÎłÎŻÎľĎ Î ÎąÎłÎşĎĎÎźÎšÎżĎ ÎĎĎÎżĎ 5Ρ δΚΏΝξΞΡ
- 2. ÎΚιδΚκιĎĎΚκΏ ÎÎą ΎθξΝινι ΟΚΝΎĎĎ ÎźÎľ ĎÎżĎ Ď ĎÎąĎικΏĎĎ ĎĎÎą ĎÎľÎťÎľĎ Ďιίι 10â ĎÎżĎ ÎźÎąÎ¸ÎŽÎźÎąĎÎżĎ petros_dv, tsakatik, mirtwza, giannis156, apostoli, kir.christos, john_efthi, gavriili, somagion, papeslis, gi0rikas, thanoskaratzas, redsoukas, ntogkasxr, thomadak
- 3. ÎΚιδΚκιĎĎΚκΏ ⢠ΠιĎικιΝĎδξίĎÎľ ĎÎżĎ Ď Î˛ÎąÎ¸ÎźÎżĎĎ ĎÎˇĎ 1Ρ ÎľĎγιĎÎŻÎąĎ ÎşÎąÎš ĎĎξίΝĎÎľ ĎĎον ÎÎťÎ˛ÎšĎ ĎĎ ĎĎν ινĎΚĎĎÎŽĎÎľÎšĎ ĎÎąĎ â˘ Î 2Ρ ÎľĎγιĎĎΡĎΚικΎ ÎŹĎκΡĎΡ θι ĎĎ ÎśÎˇĎΡθξί ĎΡν δξĎĎÎľĎΡ ĎĎÎą ĎΎΟξĎÎą, θι δĎθξί ÎąÎ˝ÎąÎťĎ ĎΚκΏ ĎÎż ÎąĎĎÎłÎľĎ ÎźÎą κιΚ θι ĎĎÎĎξΚ νι ĎÎąĎιδĎθξί ĎĎÎšĎ 8.00 ĎÎˇĎ ÎÎľĎ ĎÎĎÎąĎ.
- 4. ÎΚιδΚκιĎĎΚκΏ ΣΡΟινĎΚκΎ βοΎθξΚιγΚι ĎΡν ĎĎ Î˝ÎĎξΚι ĎÎżĎ ÎźÎąÎ¸ÎŽÎźÎąĎÎżĎ ÎşÎąÎš ΚδΚιίĎÎľĎÎą ĎĎÎż θÎΟι ĎĎν ÎľĎγιĎΚĎν θι βĎξίĎÎľ ĎĎÎą http://stackoverflow.com http://www.roseindia.net
- 5. 2Ρ ÎľĎγιĎÎŻÎą â˘ÎξΝÎĎΡĎÎľ ĎÎż 4Îż κξĎΏΝιΚο κιΚ ĎĎÎżĎΏθΡĎÎľ ĎÎż ινĎÎŻĎĎοΚĎÎż ĎÎľĎĎ. ⢠Îξκίνι ĎΡν ξΞοΚκοίĎĎÎŽ ĎÎżĎ ÎźÎľ ĎÎż https://netbeans.org ⢠ÎγκιĎÎĎĎΡĎÎľ ĎĎÎż VM ĎÎżĎ ĎĎον ÎŠÎşÎľÎąÎ˝Ď â˘ LAMP ⢠http://tomcat.apache.org ⢠Wordpress
- 6.
- 7. Being a Servlet Chapter 4
- 8. From HMTL to servlet class
- 9.
- 10. Be carefull!! getServerPort(),getLocalPort() & getRemotePort()
- 11. Response now Usethe response for I/O when ⢠There is no JSP ⢠No JSP is allowed ⢠Do not want to use JSP ⢠Do not send HTML
- 12.
- 13. Redirect sendRedirect() method: if (worksForMe) { // handle the request } else { response.sendRedirect(âhttp://www.oreilly.comâ); } Redirect is not dispatch
- 14. Being a WebApplication Chapter 5
- 15. Protecting my e-mailaddress PrintWriter out = response.getWriter(); out.println(âmav@uth.grâ); <servlet> <servlet-name>BeerParamTests</servlet-name> <servlet-class>TestInitParams</servlet-class> <init-param> <param-name>adminEmail</param-name> <param-value>mav@uth.gr</param-value> </init-param> </servlet> out.println(getServletConfig().getInitParameter(âadminEmailâ));
- 16. Servlet initializations andServletConfig The Container (after running the constructor) ⢠Creates a unique ServletConfig ⢠Reads servlet init parameters ⢠Gives them to ServletConfig ⢠Passes ServletConfig to servletâs init() method
- 17.
- 18.
- 19. Re-deploying a servlet ⢠Edit DD ⢠Shut and restart the container ⢠You better be careful what you put as init-param
- 20. Give JSP servletâsinit params ⢠As a request attribute
- 21. Give JSP servletâsinit params ⢠Using Context
- 22. Context & Servletinit parameters
- 23. Context & Servletinit parameters Container ⢠Reads DD and creates name/ value string pairs for each <context-param> ⢠Creates a new instance of ServletContext ⢠Passes (as reference) pairs to ServletContext JSP is a servlet
- 24. What else isin ServletContext?
- 25. We need alistener Which Listens for context initialization events Runs specific code before servlet starts serving Notice, there is no main()!
- 26.
- 27. Make and usea context listener Create a listener class Put the class in WEB-INF/classes Put <listener> element in DD ⢠Three classes (and one DD) ServletContextListener.java Dog.java ListenerTester.java
- 28.
- 29. Attribute class Contextinit parameters as the argument for the constructor servlet will get dog from context call getBreed() print the value of breed
- 30.
- 31. The DD (web.xmlin WEB-INF)
- 32. Compile and Deploy Compile the three classes Create a new web app in Tomcat Create ListenerTest and WEB-INF Put web.xml in WEB-INF Make a classes directory underneath. Create a directory structure that matches your package structure Put web.xml and the three compiled files into their space Shutdown and restart Tomcat
- 33.
- 35. Context & Servlet init parameters
- 36. Context & Servlet init parameters Container ⢠Reads DD and creates name/value string pairs for each <context-Ââparam> ⢠Creates a new instance of ServletContext ⢠Passes (as reference) pairs to ServletContext
- 37. What else is in ServletContext? You may get them but NOT set them later
- 38. Initializing your web application with an object After initializing with a string of course
- 39. We need a listener (a Java object) ⢠That â Listens for context initialization events â Runs specific code before servlet starts serving Notice! There is no main()
- 40.
- 41. Listen to the Dog
- 42. Make and use a context listener ⢠Create a listener class ⢠Put the class in WEB-ÂâINF/classes ⢠Put <listener> element in DD ⢠Three classes (and one DD) â ServletContextListener.java â Dog.java â ListenerTester.java
- 43.
- 44.
- 45.
- 46. The DD (the web.xml in WEB-ÂâINF)
- 47.
- 48. The whole story (In pictures)
- 49. You can listen all kinds of events
- 50. Attributes ⢠Who can put (and remove)? ⢠Who can see? ⢠For how long? SCOPE
- 51. Attributes are not Parameters!
- 52.
- 53. The 3 Scopes (API)
- 54. Beware of Attributes (1/2)
- 55. Beware of Attributes (2/2)
- 56.
- 58. Lock the Context (not the Service)
- 59.
- 60. SingleThreadModel No two threats will execute concurrently in the servletâs service method. Two choices for STM implementation
- 61. Only request attributes and local variables are thread-Ââsafe ⢠Instance variables arenât thread-Ââsafe ⢠Classes arenât thread-Ââsafe
- 62. Request attributes & Request dispatching
- 63. What is wrong here?