This document discusses servlets in Java. It defines servlets as Java classes that extend capabilities of servers by responding to requests. Servlets can process or store submitted data, provide dynamic content like database results, and manage state information in HTTP. The document outlines the servlet lifecycle and different servlet classes like GenericServlet and HttpServlet. It also describes servlet request and response objects and common methods used to access client information and send responses.

2. Disclaimer: This presentation is prepared by trainees of
baabtra as a part of mentoring program. This is not official
document of baabtra –Mentoring Partner
Baabtra-Mentoring Partner is the mentoring division of baabte System Technologies Pvt .
Ltd

3. Servlet
Abhishek H Menon
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4. Servlet
• Is a java programming language class that
used to extend the capabilities of a server.
• Can respond to any type of requests, but they
are commonly used to extend the applications
hosted by web servers.

5. Why Servlet is used?
• Process or store data that was submitted from
an html form
• Provide dynamic content such as the results of
a database query
• Manage state information that does not exist
in the stateless HTTP protocol, such as filling
the articles into the shopping cart of the
appropriate customer.

6. Diagram

7. Servlet
• In the terms of Java, Servlet is a class in J2EE
which provides all the functionalities of a
server.
• Thus a developer can use Servlet inorder to
add the dynamic content to a web server
using Java platform.
• Servlet is used as a shorthand of HTTP Servlet

8. Servlet
• Can be generated automatically from java
server pages (JSP) by the JavaServer Pages
Compiler.
• Difference between servlet and JSP is that is
that servlets typically embed HTML inside Java
code, while JSPs embed Java code in HTML.

9. How Servlet works?
Receive
request
Send
response
Is
servlet
loaded
?
Is
servlet
current
?
Process request
Load Servlet
NO
YES
NO
YES

10. Servlet APIs
• Every servlet must implement
javax.servlet.Servlet interface
• Most servlets implement the interface by
extending one of these classes
–javax.servlet.GenericServlet
–javax.servlet.http.HttpServlet

11. Generic and HTTP Servlet
browser
browser
server
HTTP
server
request
request
response
response
HTTP Servlet
Generic Servlet
service()
doGet()
doPost()
service()

12. Generic servlet methods
• void init(ServletConfig config)
– Initializes the servlet.
• void service(ServletRequest req, ServletResponse res)
– Carries out a single request from the client.
• void destroy()
– Cleans up whatever resources are being held (e.g., memory, file
handles, threads) and makes sure that any persistent state is
synchronized with the servlet's current in-memory state.
• ServletConfig getServletConfig()
– Returns a servlet config object, which contains any initialization
parameters and startup configuration for this servlet.
• String getServletInfo()
– Returns a string containing information about the servlet, such as its
author, version, and copyright.
Life cycle
methods
of Servlet

13. Servlet Lifecycle
Initialization
init()
Service
service()
doGet()
doPost()
doDelete()
doHead()
doTrace()
doOptions()
Destruction
destroy()
Concurrent
Threads
of Execution

14. HttpServlet - Methods
• void doGet (HttpServletRequest request,
• HttpServletResponse response)
– handles GET requests
• void doPost (HttpServletRequest request,
• HttpServletResponse response)
– handles POST requests
• void doPut (HttpServletRequest request,
• HttpServletResponse response)
– handles PUT requests
• void doDelete (HttpServletRequest request,
• HttpServletResponse response)
– handles DELETE requests

15. Servlet Request Objects
• provides client request information to a servlet.
• the servlet container creates a servlet request object and
passes it as an argument to the servlet's service method.
• the ServletRequest interface define methods to retrieve data
sent as client request:
– parameter name and values
– attributes
– input stream
• HTTPServletRequest extends the ServletRequest interface to
provide request information for HTTP servlets

16. HttpServletRequest - Methods
Enumeration getParameterNames()
an Enumeration of String objects, each
String containing the name of a request
parameter; or an empty Enumeration if
the request has no parameters
java.lang.String[] getParameterValues (java.lang.String
name)
Returns an array of String objects
containing all of the values the given
request parameter has, or null if the
parameter does not exist
java.lang.String getParameter (java.lang.String name)
Returns the value of a request
parameter as a String, or null if the
parameter does not exist.

17. HttpServletRequest - Methods
Cookie[] getCookies()
Returns an array containing all of the Cookie
objects the client sent with this request.
java.lang.String getMethod()
Returns the name of the HTTP method with
whichthi request was made, for example,
GET, POST, or PUT.
java.lang.String getQueryString()
Returns the query string that is contained in
the request URL after the path.
HttpSession getSession()
Returns the current session associated with
this request, or if the request does not have a
session, creates one.

18. Servlet Response Objects
• Defines an object to assist a servlet in sending
a response to the client.
• The servlet container creates a
ServletResponse object and passes it as an
argument to the servlet's service method.

19. HttpServletResponse - Methods
java.io.PrintWriter getWriter()
Returns a PrintWriter object that
can send
character text to the client
void setContentType
(java.lang.String type)
Sets the content type of the
response being sent to the
client. The content type may
include the type of character
encoding used, for example,
text/html; charset=ISO-8859-4
int getBufferSize()
Returns the actual buffer size
used for the response

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