1. Java Server Pages

2. JSP
Java Server Pages (JSP) is a server-side programming technology that enables the creation of dynamic and platform-independent Web based applications.
Support dynamic content which helps developers insert java code in HTML pages by making use of special JSP tags.

3. JSP

4. JSPs Vs Servlets
JSP is nothing but a high-level abstraction of servlets. You can do almost anything that can be done with servlets using JSP--but more easily!

5. JSP page translation and processing phases
Translation phase
Hello.jsp
Read
Request
Client
Server
helloServlet.java
Generate
Response
Execute
Processing phase
helloServlet.class

6. JSP Life Cycle

7. JSP Comments
JSP comment marks text or statements that the JSP container should ignore.
A JSP comment is useful when you want to hide or "comment out" part of your JSP page.
Following is the syntax of JSP comments:
<%-- This is JSP comment --%>

8. JSP Elements
Java Server Pages are HTML pages embedded with snippets of Java code.
It is an inverse of a Java Servlet
Elements are used in constructing JSPs
Scripting Elements
Implicit Objects
Directives
Prevention: locks at doors, window bars, walls round the property
Detection: stolen items are missing, burglar alarms, closed circuit TV
Reaction: call the police, replace stolen items, make an insurance claim …
Prevention: encrypt your orders, rely on the merchant to perform checks on the caller, don’t use the Internet (?) …
Detection: an unauthorized transaction appears on your credit card statement
Reaction: complain, ask for a new card number, etc.

9. Scripting Elements :Types
There are three kinds of scripting elements
Declarations
Scriptlets
Expressions
Prevention: locks at doors, window bars, walls round the property
Detection: stolen items are missing, burglar alarms, closed circuit TV
Reaction: call the police, replace stolen items, make an insurance claim …
Prevention: encrypt your orders, rely on the merchant to perform checks on the caller, don’t use the Internet (?) …
Detection: an unauthorized transaction appears on your credit card statement
Reaction: complain, ask for a new card number, etc.

10. Expressions Basics Used to write dynamic content back to the browser.
If the output of expression is Java primitive the value is printed back to the browser
If the output is an object then the result of calling toString on the object is output to the browser
Embedded in <%= and %> delimiters
Example:
<%=“Fred”+ “ “ + “Flintstone” %>
prints “Fred Flintstone” to the browser
<%=Math.sqrt(100)%>
prints 10 to the browser
Prevention: locks at doors, window bars, walls round the property
Detection: stolen items are missing, burglar alarms, closed circuit TV
Reaction: call the police, replace stolen items, make an insurance claim …
Prevention: encrypt your orders, rely on the merchant to perform checks on the caller, don’t use the Internet (?) …
Detection: an unauthorized transaction appears on your credit card statement
Reaction: complain, ask for a new card number, etc.

11. Declarations Basics
Declarations are used to define methods & instance variables
Embedded in <%! and %> delimiters
Example:
<%! int data=50; %>
<%= "Value of the variable is:"+data %>
<%!
int cube(int n){
return n*n*n; }
%>
<%= "Cube of 3 is:"+cube(3) %>
Prevention: locks at doors, window bars, walls round the property
Detection: stolen items are missing, burglar alarms, closed circuit TV
Reaction: call the police, replace stolen items, make an insurance claim …
Prevention: encrypt your orders, rely on the merchant to perform checks on the caller, don’t use the Internet (?) …
Detection: an unauthorized transaction appears on your credit card statement
Reaction: complain, ask for a new card number, etc.

12. Scriptlets Used to embed java code in JSP pages.
Code should comply with syntactical and semantic constuct of java
Any code written inside the scriptlet tags go into the _jspService() method.
Embedded in <% and %> delimiters
Example:
<%
int x = 5;
int y = 7;
int z = x + y;
%>
System.out.println( "Evaluating date now" );
java.util.Date date = new java.util.Date();
Hello! The time is now <%= date %>
Prevention: locks at doors, window bars, walls round the property
Detection: stolen items are missing, burglar alarms, closed circuit TV
Reaction: call the police, replace stolen items, make an insurance claim …
Prevention: encrypt your orders, rely on the merchant to perform checks on the caller, don’t use the Internet (?) …
Detection: an unauthorized transaction appears on your credit card statement
Reaction: complain, ask for a new card number, etc.

13. JSP Directives The page directive The include directive
A JSP directive affects the overall structure of the servlet class. It usually has the following form:
directive attribute="value" %>
The page directive 
The include directive

14. JSP Directives Page Directive Example :
Page directive specifies the instructions which applies to the entire source file , to the JSP engine.
Example :
page language="java“ import="java.util.*>
Attributes

15. Attribute
Purpose
buffer
Specifies a buffering model for the output stream.
autoFlush
Controls the behavior of the servlet output buffer.
contentType
Defines the character encoding scheme.
errorPage
Defines the URL of another JSP that reports on Java unchecked runtime exceptions.
isErrorPage
Indicates if this JSP page is a URL specified by another JSP page's errorPage attribute.
extends
Specifies a superclass that the generated servlet must extend
import
Specifies a list of packages or classes for use in the JSP as the Java import statement does for Java classes.
info
Defines a string that can be accessed with the servlet's getServletInfo() method.
isThreadSafe
Defines the threading model for the generated servlet.
language
Defines the programming language used in the JSP page.
session
Specifies whether or not the JSP page participates in HTTP sessions
isELIgnored
Specifies whether or not EL expression within the JSP page will be ignored.
isScriptingEnabled
Determines if scripting elements are allowed for use

16. JSP Directives include Directive:
The include directive is used to includes a file during the translation phase.
This directive tells the container to merge the content of other external files with the current JSP during the translation phase.
Example:
include file="header.jsp" %>
<p>Thanks for visiting my page.</p>
include file="footer.jsp" %>

17. Java Implicit Objects Scope
Implicit objects provide access to server side objects
e.g. request, response, session etc.
There are four scopes of the objects
Page: Objects can only be accessed in the page where they are referenced
Request: Objects can be accessed within all pages that serve the current request.
(Including the pages that are forwarded to and included in the original jsp page)
Session: Objects can be accessed within the JSP pages for which the objects are defined
Application: Objects can be accessed by all JSP pages in a given context
Prevention: locks at doors, window bars, walls round the property
Detection: stolen items are missing, burglar alarms, closed circuit TV
Reaction: call the police, replace stolen items, make an insurance claim …
Prevention: encrypt your orders, rely on the merchant to perform checks on the caller, don’t use the Internet (?) …
Detection: an unauthorized transaction appears on your credit card statement
Reaction: complain, ask for a new card number, etc.

18. Java Implicit Objects request: Reference to the current request
response: Response to the request
session: session associated woth current request
application: Servlet context to which a page belongs
pageContext: Object to access request, response, session and application associated with a page
config: Servlet configuration for the page
out: Object that writes to the response output stream
page: instance of the page implementation class (this)
exception: Available with JSP pages which are error pages
Prevention: locks at doors, window bars, walls round the property
Detection: stolen items are missing, burglar alarms, closed circuit TV
Reaction: call the police, replace stolen items, make an insurance claim …
Prevention: encrypt your orders, rely on the merchant to perform checks on the caller, don’t use the Internet (?) …
Detection: an unauthorized transaction appears on your credit card statement
Reaction: complain, ask for a new card number, etc.

19. The out Object:
Following are the important methods which we would use to write boolean char, int, double, object, String etc.
Method
Description
out.print(dataType dt)
Print a data type value
out.println(dataType dt)
Print a data type value then terminate the line with new line character.
out.flush()
Flush the stream.

20. Methods of Request object
getParameter(): You call request.getParameter() method to get the value of a form parameter.
getParameterValues(): Call this method if the parameter appears more than once and returns multiple values, for example checkbox.
getParameterNames(): Call this method if you want a complete list of all parameters in the current request.
getInputStream(): Call this method to read binary data stream coming from the client.

21. DEMO