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Java Server PagesJSP
• Introduction
• JSP Architecture
• Scripting Elements
• Directives
• Implicit Objects
2
Agenda
• A way to create dynamic web pages
• Separates the graphical design from the dynamic content
• A JSP page is a text document that contains:– Static data (such as HTML, WML, and XML)
– JSP elements, which construct dynamic content.
3
Introduction
First Look at Code<html>
<body>
I am HTML code. <br>
<b><% out.println("I am JSP Code"); %></b><br>
<b><% out.println("Today date & time is: "+java.time.LocalDateTime.now()); %></b>
</body>
</html>
4
Processing
5SRC:https://www.tutorialspoint.com/jsp/jsp_architecture.htm
Life Cycle
6SRC: https://www.tutorialspoint.com/jsp/jsp_life_cycle.htm
JSP/Servlet CorrespondenceOriginal JSP<%= printme() %>
<% callme(); %>
Possible resulting servlet codepublic void _jspService(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
request.setContentType("text/html");
HttpSession session = request.getSession(true);
JspWriter out = response.getWriter();
out.println(printme());
callme();
...
}7
API• Packages
– javax.servlet.jsp
– javax.servlet.jsp.tagext
• javax.servlet.jsp package– Interfaces
– JspPage
– HttpJspPage
– Classes– JspWriter
– PageContext
– JspFactory
– JspEngineInfo
– JspException
– JspError
8
Components
• Scripting Elements
• Directives
• Implicit Objects
• Actions
9
Scripting Elements• Provides the ability to insert java code inside the jsp
• Three forms:
– Expressions of the form <%= expression %> that are evaluated and inserted into the output
– Scriptlets of the form <% code %> that are inserted into the servlet's service method
– Declarations of the form <%! code %> that are inserted into the body of the servlet class, outside of any existing methods.
10
Expression• <% = expression %>
• <jsp:expression>
expression
</jsp:expression>
Example:
11
<%= java.time.LocalDate.now() %>
Scriptlet• <% code fragment %>
• <jsp:scriptlet>
code fragment
</jsp:scriptlet>
Example:
12
<% out.println("Your IP address is " + request.getRemoteAddr());
%>
Declaration• <% ! declaration; %>
• <jsp:declaration>
• code fragment
• </jsp:declaration>
13
<%! int i = 0; %>
<%! int i; %>
<%! Student student = new Student(); %>
<%! int area(int a, int b){
return a*b;
}
%>
Example: Math.html
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<form method="post" action="Math.jsp">
<input type="radio" name=“operator" value="add" checked>Addition<br>
<input type="radio" name=“operator" value=“subtract" >Subtraction<br>
<input type="radio" name=“operator" value="multiply" >Multiplication<br>
<input type="radio" name="operator" value="divide" >Division<br>
<br><br>
Enter first Value <input type="text" name=“input1" value=""><br>
Enter second Value <input type="text" name=“input2" value=""><br>
<input type="submit" name="result">
</form>
Example: Math.jsp
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<body><%!int number1, number2, result;%><H1> Result for <%=request.getParameter("operator")%></H1><%
number1 = Integer.parseInt(request.getParameter("input1"));number2 = Integer.parseInt(request.getParameter("input2"));result = 0;String str = request.getParameter("operator");
if (str.equals("add")) {result = number1 + number2;
}if (str.equals("subtract")) {
result = number1 - number2;}if (str.equals("multiply")) {
result = number1 * number2;}
if (str.equals("divide")) {result = number1 / number2;
}
%>Result is <%=result%>
</body>
Directives • Affects the overall structure of the servlet class
• Tells the web container how to translate a JSP page into the corresponding servlet.
• <%@ directive attribute="value" %>
16
<%@ page ... %> Defines attributes that apply to an entire JSP page.
<%@ include ... %> Includes a file during the translation phase.
<%@ taglib ... %> Declares a tag library, containing custom actions, used in the page
Page Directive• <%@ page attribute="value" %>
• <jsp:directive.page attribute="value" />
• Example:
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<%@ page extends=“myClass”
import=‘java.util.*”
contentType=“text/html”
errorPage=“error.jsp”
%>
Page directive
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Directives Values Description
Language scriptingLanguage The default value is "java".
Extends classname
Import importList java.lang.*, javax.servlet.*, javax.servlet.jsp.*,
and javax.servlet.http.* are imported
implicitily
Session true|false
Buffer none|sizekb Default 8 kb
autoFlush true|false
isThreadSafe true|false
Info info_text retrieved later by using getServletInfo()
method
errorPage error_URL
isErrorPage true|false
contentType contentInfo
pageEncoding pageEncodingInfo
errorPage & isErrorPage• Authenticate.html
• Authenticate.jsp
• LoginErrorPage.jsp
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<%@ page errorPage="LoginErrorPage.jsp" %>
<%@ page isErrorPage="true" %>
Include Directive• Includes a static file
<%@ include file="relative url" >
<jsp:directive.include file="relative url" />
Example:
main.jsp:
date.jsp:
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Current date and time is: <%@include file=“date.jsp”
<%@page import =“java.util.*” %><% =(new java.util.Date()).toLocaleString() %>
Implicit Objects
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Object Description
request This is the HttpServletRequest object associated with the request.
response This is the HttpServletResponse object associated with the response to the client.
out This is the PrintWriter object used to send output to the client.
session This is the HttpSession object associated with the request.
application This is the ServletContext object associated with application context.
config This is the ServletConfig object associated with the page.
pageContext This encapsulates use of server-specific features like higher performance JspWriters.
page This is simply a synonym for this, and is used to call the methods defined by the translated servlet class.
Exception The Exception object allows the exception data to be accessed by designated JSP.
References
• https://docs.oracle.com/javaee/5/tutorial/doc/bnagx.html
• https://www.javatpoint.com/jsp-tutorial
22
Thank you
23
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