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Introduction to JSP.pptx

  1. Introduction to JSP  JSP technology is used to create web application just like Servlet technology.  It can be thought of as an extension to Servlet because it provides more functionality than servlet such as expression language, JSTL, etc.  A JSP page consists of HTML tags and JSP tags. The JSP pages are easier to maintain than Servlet because we can separate designing and development.  It provides some additional features such as Expression Language, Custom Tags, etc.
  2. Advantages of JSP over Servlet  Extension to Servlet  Easy to maintain  Fast Development: No need to recompile and redeploy  Less code than Servlet
  3. The Lifecycle of a JSP Page
  4.  Translation of JSP Page  Compilation of JSP Page  Classloading (the classloader loads class file)  Instantiation (Object of the Generated Servlet is created).  Initialization ( the container invokes jspInit() method).  Request processing ( the container invokes _jspService() method).  Destroy ( the container invokes jspDestroy() method).  jspInit(), _jspService() and jspDestroy() are the life cycle methods of JSP.
  5. The Directory structure of JSP
  6. Implicit Objects  JSP Out  JSP Request  JSP Response  JSP Config  JSP Application  JSP Session  JSP PageContext  JSP Page  JSP Exception
  7. Implicit Objects  Out For writing any data to the buffer, JSP provides an implicit object named out. It is the object of JspWriter.  Request The JSP request is an implicit object of type HttpServletRequest i.e. created for each jsp request by the web container. It can be used to get request information such as parameter, header information, remote address, server name, server port, content type, character encoding etc.  JSP response implicit object In JSP, response is an implicit object of type HttpServletResponse. The instance of HttpServletResponse is created by the web container for each jsp request.
  8.  Config In JSP, config is an implicit object of type ServletConfig. This object can be used to get initialization parameter for a particular JSP page. The config object is created by the web container for each jsp page. <web-app> <servlet> <servlet-name>servlet</servlet-name> <jsp-file>/welcome.jsp</jsp-file> </servlet> <servlet-mapping> <servlet-name>servlet</servlet-name> <url-pattern>/welcome</url-pattern> </servlet-mapping>
  9. application  In JSP, application is an implicit object of type ServletContext.  The instance of ServletContext is created only once by the web container when application or project is deployed on the server.  This object can be used to get initialization parameter from configuaration file (web.xml). It can also be used to get, set or remove attribute from the application scope.  This initialization parameter can be used by all jsp pages.
  10. pageContext  Using this object you can find attribute, get attribute, set attribute and remove attribute at any of the below levels –  JSP Page – Scope: PAGE_CONTEXT  HTTP Request – Scope: REQUEST_CONTEXT  HTTP Session – Scope: SESSION_CONTEXT  Application Level – Scope: APPLICATION_CONTEXT
  11. Methods of pageContext  Object findAttribute (String AttributeName)  Object getAttribute (String AttributeName, int Scope) Object obj = pageContext.getAttribute("BeginnersBook", PageContext.SESSION_CONTEXT)  void removeAttribute(String AttributeName, int Scope) pageContext.removeAttribute(“MyAttr”, PageContext. PAGE_CONTEXT);  void setAttribute(String AttributeName, Object AttributeValue, int Scope): pageContext.setAttribute(“mydata”, “This is my data”, PageContext. APPLICATION_CONTEXT);
  12. Session object  In JSP, session is an implicit object of type HttpSession.The Java developer can use this object to set,get or remove attribute or to get session information.
  13. Page object  Page implicit variable holds the currently executed servlet object for the corresponding jsp.  Acts as this object for current jsp page.
  14. Exception object  Exception is the implicit object of the throwable class.  It is used for exception handling in JSP.  The exception object can be only used in error pages
  15. Scripting Elements  The scripting elements provides the ability to insert java code inside the jsp. There are three types of scripting elements:  scriptlet  expression  Declaration  comments
  16. Scriplets  Scriptlets are nothing but java code enclosed within <% and %> tags.  JSP container moves the statements enclosed in it to _jspService() method while generating servlet from JSP.
  17. Declaration  Declaration tag is a block of java code for declaring class wide variables, methods and classes.  Whatever placed inside these tags gets initialized during JSP initialization phase and has class scope.  JSP container keeps this code outside of the service method (_jspService()) to make them class level variables and methods.  Syntax of declaration tag: <%! Declaration %>
  18. Expression  Expression tag evaluates the expression placed in it, converts the result into String and send the result back to the client through response object.  Basically it writes the result to the client(browser).  Syntax <%= expression %> Example <html> <head> <title>JSP expression tag example1</title> </head> <body> <%= 2+4*5 %> </body> </html>
  19. JSP Directives  Directives control the processing of an entire JSP page. It gives directions to the server regarding processing of a page.  There are three types of Directives in JSP: 1) Page Directive 2) Include Directive 3) TagLib Directive
  20. Page Directive  There are several attributes, which are used along with Page Directives and these are –  Import <%@page import="value"%> Example <%@page import="*%> <%@page import="java.lang.*%> Or <%@page import="*, java.lang.*"%>  Session <%@ page session="false"%>  isErrorPage <%@ page isErrorPage="value"%>  errorPage <%@ page errorPage="value"%>
  21.  ContentType This attribute is used to set the content type of a JSP page.  isThreadSafe It is used to allow multithreading which means only single thread will execute the page code.  extends  Info It provides a description to a JSP page. The string specified in info will return when we will call getServletInfo() method.  Language It specifies the scripting language( underlying language) being used in the page.  Autoflush  Buffer This attribute is used to specify the buffer size.
  22. Include Directive  Include directive is used to copy the content of one JSP page to another. It’s like including the code of one file into another. <%@include file ="value"%>
  23. Action tag  Each JSP action tag is used to perform some specific tasks.  The action tags are used to control the flow between pages and to use Java Bean.  JSP Actions - jsp:forward , jsp:include, jsp:useBean, jsp:setProperty and jsp:getProperty
  24. jsp:forward action tag  The jsp:forward action tag is used to forward the request to another resource it may be jsp, html or another resource.  Syntax <jsp:forward page="relativeURL | <%= expression %>" />
  25. jsp:include action tag  The jsp:include action tag is used to include the content of another resource it may be jsp, html or servlet.  Difference between include directive and include action tag include directive Include action tag includes resource at translation time. includes resource at request time. better for static pages. better for dynamic pages.
  26.  Workshop on Spring framework  Date :18/06/2022  Time : 8:30-10:30  Mode : online  Platform : MS-Teams