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JSP Overview: Server-Side Technology for Dynamic Webpages

Learn about Java Server Pages (JSP), a server-side technology that allows web programmers to generate webpages dynamically. Understand the JSP lifecycle, JSP elements, directives, tag libraries, and action elements.

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JSP Overview: Server-Side Technology for Dynamic Webpages

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  1. Unit-vi & viiJava server pages

  2. Jsp is server side technology that enables web programmers to generate webpages dynamically in response to client requests. • Jsp is nothing but high level abstraction of java servlet technology. • Jsp pages run under the supervision of an environment called web container. • web container compiles the page on the server and generates servlet, which is loaded in the JRE. • Jsp technology provides excellent server side programming for web applications that need a database access.

  3. JSP Overview - Servlets v/s JSPs JSPs : Java within HTML Presentation logic Servlets : HTML within Java business logic public void doGet(request, response) { PrintWriter out = response.getWriter(); String name = request.getParameter(name); out.println(“<html><body>”); out.println("Hello” + name); out.println(“</body></html>”); } <html> <body> <% String name = request.getParameter(name); %> Hello <%= name %> </body> </html>

  4. JSP Overview - What is a JSP In the end, a JSP is just a Servlet. Is loaded and Initialized as Is translated to Compiles to writes JSP Import javax. servlet. HttpServlet.* 0010 0001 1100 1001 0001 0011 Servlet MyJsp_jsp Servlet MyJsp.jsp MyJsp_jsp.java MyJsp_jsp.class

  5. JSP Life Cycle JSP page (MyFirstJSP.jsp) -> Translated to Servle(MyFirstJSP.servlet) -> Compiled to class (MyFirstJSP.class) -> Loaded into memory (Initialization) -> Execution (repeats) -> Destruction Any change in JSP page automatically repeats the whole life cycle.

  6. jsp anatomy /components Jsp page is a simple web page which contains the jsp elements & template text • Template data: every thing in the web page what the jsp container doesn’t understand is called template data. • Template text can be scripting code such as html,wml,xml (or)simple text • Jsp elements:

  7. Jsp elements:

  8. Directives: • Directives: a jsp may contain instructions to be used by the jsp container to indicate how this page is interpreted and executed. Those instructions are called Directives • Delimited by <%@ and %>

  9. page Directive • Specifies JSP’s global settings in JSP container • First line of a JSP file • Example: • <%@ Directive attribute=“value –of _attribute”%> • <%@ page language=“java” contentType=“text/html” %>

  10. page Directive

  11. page Directive (cont.)

  12. include Directive • Includes content of another resource at JSP translation time • Not as flexible as <jsp:include> action • <tr> <td style = "width: 160px"> <%-- include toc.html in this JSP --%>//commments <%@include file ="toc.html"%> </td> <td style = "vertical-align: top"> <%-- include clock2.jsp in this JSP --%> <%@include file ="clock2.jsp" %> </td> </tr>

  13. Tag lib • It is used to specify the custom tags. The custom tags are those tags that can be created by the user. • <% taglib uri=“taglibraryURI” prefix=“tagPrefix” %> • http://www.tutorialspoint.com/jsp/jsp_standard_tag_library.htm

  14. Action elements • The elements which are used to access the bean in page is called JSP action elements. • Standard Actions • Custom actions • Jsp standard tag library

  15. Standard Actions • Predefined JSP tags that encapsulate functionality • Provide access to common tasks performed in a JSP • Including content from other resources • Forwarding requests to other resources • Interacting with JavaBeans • JSP containers process actions at request time • Delimited by <jsp:action> and </jsp:action> • Often performed based on information from client request

  16. Standard Actions

  17. Standard Actions (cont.)

  18. <jsp:include> Action • Enables dynamic content to be included in a JSP • More flexible than include directive • Requires more overhead when page contents change frequently • Example: • <Html> • <head></head> • <Body> • <jsp:include page="banner.html" flush="true" /></body></html>

  19. <jsp:forward> & <jsp:param> Actions • <jsp:forward> action • Enables JSP to forward request to different resource • <jsp:param> action • Specifies name/value pairs of information to pass to other actions • Example:<jsp:forward page=“forward2.jsp"> <jsp:param name = "date" value = "<%= new java.util.Date() %>" /> </jsp:forward>

  20. <jsp:plugin> Action <html> <head> <title>Using jsp:plugin to load an applet</title> </head> <body> <jsp:plugin type = "applet" code = "com.deitel.advjhtp1.jsp.applet.ShapesApplet" codebase = "/advjhtp1/jsp" width = "400" height = "400"> <jsp:params> <jsp:param name = "red" value = "255" /> <jsp:param name = "green" value = "255" /> <jsp:param name = "blue" value = "0" /> </jsp:params> </jsp:plugin> </body> </html> • Adds an applet or JavaBean to a Web page

  21. Custom actions • Custom action element allows us to create user –defined tags. • The programmer can hide the java class code and can acess that code from the jsp page

  22. Jsp standard tag library • JSTL standard for jsp tag library. • J2ee is typically used for server side programming using java and JSTL a component of J2EE web application development platform. • Tag library is useful for performing some common tasks such as condition execution, loop execution, data procession….. • Core • Xml • Sql • Formatting • Functions • http://www.tutorialspoint.com/jsp/jsp_standard_tag_library.htm.

  23. Core • The core tag is used nearly in all the web applications. • Tag is useful for performing basic input & output, for looping operation or evaluating expression.

  24. Jsp Example • A simple jsp program to display date and time •   <%@ page language="java" contentType="text/html"%> • <%@ page import="java.lang.*" import="java.util.*"%> • <html> • <head> • <title> laxmi first JSP Pro</title> • </head> • <body> • <h1> Welcome to my First JSP Program</h1> • <%out.println("JSP is equal to HTML and JAVA");%> • <%= new Date()%> • </body> • </html>

  25. scriptlets • Scripting elements means writing java code in jsp. • Three type of elements: • Scriptlet • Expressions • Declarations

  26. Implicit Objects • Implicit Objects are predefined variables used to access request application data. These objects are used by the scripting elements. • Objects created by the servlet container • Application • Session • Request • Response • Exception • Out • Config • Pagecontext • Page

  27. Application Object • Used to share data between all of the pages that make up an application • All users share the Application Object • Can be accessed from any JSP in the application via the ServletContext • javax.servlet.http.ServletContext

  28. Application Object Methods • getAttribute(String name) • getAttributeNames • setAttribute(String objName, Object object) • removeAttribute(String objName) • getMajorVersion() • getMinorVersion() • getServerInfo() • getInitParameter(String name) • getInitParameterNames • getResourceAsStream(Path) • log(Message)

  29. Sessions • A session is a concept that represents a series of HTTP requests and responses between a specific browser and a specific server. • Sessions are managed by the server • Created by the server when the first request is received from a browser on a new host the server starts the session and assigns it an ID. • The ID is sent to the browser as a cookie and remembered by the server

  30. Sessions (more) • The server creates a Session object that contains the attributes: • Creation Time • ID • Last Time Accessed • Maximum Inactive Time allowed. • Javax.servlet.http.HttpSession

  31. HTTPSession Interface • getAttribute() – returns the object associated with the specified key string • getAttributeNames() – returns an enumeration of the key strings in the session • getCreationTime() – returns the time the session was created; millsecs past midnight since Jan 1, 1970 GMT • getID() – returns the session ID as a string • getLastAccessedTime() – returns thelast time the client sent a request for this session • setAttribute() – associates an object with a key string in the session • removeAttribute() – remove an attribute from the session

  32. request Object • Javax.servlet. http.httpservletrequest. • The object request is of type Javax.servlet.http.httpservletrequest. • This denotes the data included with the HTTP Request. • The client makes a request that is then passed to the server. • The requested object is used to take the value from client’s web browser and pass it to the server. • This is performed using HTTP request like headers, cookies and arguments. • Methods: • getContentLength() • getServerName()

  33. response Object • Javax.servlet.http.HttpServletResponse • The HTTP Response data. • The result or the information that fulfills an Http request • The object response is of type javax.servlet.http. httpservletresponse. Generally, the object response is used with cookies. The response object is used to build the HTTP response header • Methods: • addCookie() • AddHeader()

  34. pageContext Object • Javax.servlet.jsp.pagecontext • Used to access page attributes and also to access all the namespaces associated with a JSP page. • Methods: • getRequest() • getpage() • getResponse()

  35. Out Object • The Output stream in the context of page. • The class or the interface name of the Out object is jsp.JspWriter. • The Out object is written: Javax.servlet.jsp.JspWriter • Methods: • Clear() • newLine()

  36. config Object • This is used to get information regarding the Servlet configuration • The class or the interface name of the Config object is ServletConfig. • The object Config is written Javax.servlet.http.ServletConfig • Methods: • getinitParameter() • getServletName()

  37. page Object • The Page object denotes the JSP page • Used for calling any instance of a Page's servlet. • The class or the interface name of the Page object is jsp.HttpJspPage. • The Page object is written: Java.lang.Object

  38. Exception • This object is for handling error pages and contain information about runtime error

  39. Conditional processing(scriptlet) • To build the complex logic we require some conditional statements. • We can embed the java conditional statements in the jsp. this task can be done by scriptlets. • Scriptlets allows us to embed the java code in the jsp page. • Syntax: • <% any code %> • <%@ page language="java" contentType="text/html"%> • <%@ page import="java.lang.*" import="java.util.*"%> • <html><head> • <title> laxmi first scriplet</title> • </head><body> • <h1> Welcome to my First scriplet Program</h1> • <%out.println("JSP is very interesting");%> • </body></html>

  40. <%@ page language="java" contentType="text/html"%> • <%@ page import="java.lang.*" import="java.util.*"%> • <html><head> • <title> laxmi second scriplet</title> • </head><body> • <h1> Welcome to my second scriplet Program</h1> • <strong> • <%out.println(“value of I is:");%> • <%for(int i=1;i<5;i++){ • Out.print(“<br/>”); • If(i%2==0) • { • Out.print(“<i/>”); • Out.println(“Even value is : “+i); • } • else • { • Out.print(“<i/>”); • Out.println(“Odd value is : “+i); • } • }%> • </strong> • </body></html>

  41. Output: • Value of I is : • Odd value is :1 • Even value is:2 • Odd value is:3 • Even value is :4

  42. Displaying values using an expression to set an attribute • The Jsp expressions are used to insert java values directly into the output. • Syntax: • <%=expressioncode%> • Expression gets evaluated at run time and then the result will get displayed on the web browser. • <%@ page language="java" contentType="text/html"%> • <html><head> • <title> int to expression</title> • </head><body> • <h1> Welcome to expression</h1> • <strong> • Now the date and time is = <% new java.util.date()%> • </strong> • </body> </html>

  43. <%= request.getServerName()%> (implict object are used) • <%= request.getServerport()%> (implict object are used)

  44. Declaring variables and methods • Jsp allows us to use the user defined variables and methods using declaration. • The variables and methods can be used along with the scriptlets and expression. • Syntax:<%! Any java code%> • <%@ page language="java" contentType="text/html"%> • <%! • String msg=“hello”;%> • <%! Public String MyFunction(String msg) • { return msg; } %> • <html> <title> use of methods</tilte>></head> • <body> <% out.print(“before function call:”+msg);%> • <br/> After function call: <% =MyFuncion(“technical pub”)%></body></html>

  45. ERROR DEUGGING • <%@page language="java" contentType="text/html"> • <%@page import="java.util.*"%> • <html> • <body> • Today's Date is: • <%=new Date().toString()%> • </body> • </html>

  46. Scriptlet demo • <%@page language="java" contentType="text/html"%> • <html> • <head> • <title>Introduction to SCRITPTLET</title> • </head> • <body> • <h1> • <%ou.println(" HIIIIIIIII ");%> • </h1> • </body> • </html>

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