about servlets api overview

1. SERVLETS API OVERVIEW
PRESENTED BY
M.RAMYA
M.sc (CS & IT)
NADAR SARASWATHI COLLEGE OF ARTS &
SCIENCE,
THENI.

2. SERVLETS
• Servlets used to create web application
• Servlets are middle layer of between a request from browser or
HTTP client and database application.
• Servlets are robust and scalable
• Servlets are platform independent
• Servlets resides at server side and generates dynamic web page

3. • Servlets are used to collect input through the web forms or to
show records from database via web reports.
• Servlets performance is significantly better than CGI.
• Servlets execute within the address space of a Web server. So
it is not necessary to create a separate process to handle each
client request.
• Servlets are secure.

4. SERVLETS – DIAGRAMMATIC REPRESENTATION
Web browser HTTP Server
Servlet Program
Database

5. SERVLETS EXECUTION STEPS :
• Browser or any HTTP client sent data to the HTTP Server in the form of Web Page.
• The request sent by the Browser or client is read by Servlets. Request or data sent
includes
• Servlet then processes the data and generate the results.
• Servlet then Sends data to the clients (browsers) in verity of formats which
includes web page, Images, pdf or excel
No. Request Sent by Browser includes
1 HTML Form
2 cookies
3 media types
4 compression schemes etc

6. DIFFERENT TERMS USED IN SERVLET
TECHNOLOGY :
Term Description
HTTP Protocol
allows web servers and browsers to
exchange data over the web
Get and Post method
Methods for a request-response data
between a client and server
Container
Run time environment for Java EE
applications
Application Server
A server that exposes business logic to
client applications through various
protocols including HTTP.
Web Server A server that handles HTTP protocol.
Content Type
HTTP header which provides the
description about what are you sending to
the browser.
Deployment
Activity by which make a web application
available for use

7. SERVLET API
• Before creating the first servlets, you need to understand the
Servlet API and Tomcat Servlet container. The Servlet API
provides interfaces and classes that are required to built
servlets. These interfaces and classes are group into the
following two packages :
• javax.servlet
• javax.servlet. Http

8. JAVAX.SERVLET PACKAGE
• The javax.Servlet package contains a number of interfaces and
classes that establish the framework in which servlets operate.
The classes and interface in this package are protocol
independent. The Fig. shows classes and interfaces in this
package.

10. The javax.servlet package contains many interfaces and
classes. Some of the interfaces and classes are listed in table.
Interfaces Description
Servlet Declares life cycle methods that all
servlets must implement.
ServletConfig Allows servlets to get initialization
parameters
ServletContext Allows servlets to communicate
with its servlet container.
ServletRequest Provides client request information
to a servlet.
ServletResponse Assist a servlet in sending a
response to the client.

11. Classes Description
GenericServlet Provides a basic implementation of the
Servlet interface for protocol
independent servlets
ServletlnputStream Provides an input stream for reading
binary data from a client request.
ServletOutputStream Provides an output stream for sending
binary data to the client.
ServletException Defines a general exception, a servlet
can throw when it encounters
difficulty.
UnavailableException Indicates that a servlet is not available
to service client request.

12. WRITING SERVLETS
• Servlet is an extension to a server that enhances the server's
functionality. The most common use for a servlet is to extend a
web server by providing dynamic web content
• . Web servers display documents written in HyperText Markup
Language (HTML) and respond to user requests using the
HyperText Transfer Protocol (HTTP).
• HTTP is the protocol for moving hypertext files across the
internet. HTML documents contain text that has been marked
up for interpretation by an HTML browser such as Netscape.

13. SIMPLE SERVLETS HANDLING HTML
• Handling form data represented in HTML page is a very
common task in web development. A typical scenario is the
user fills in fields of a form and submits it.
• The server will process the request based on the submitted
data, and send response back to the client.

14. • To create a form in HTML we need to use the following tags:
– <form>: to create a form to add fields in its body.
– <input>, <select>, <text area>…: to create form fields like
text boxes, dropdown list, text area, check boxes, radio
buttons,… and submit button.