Java ppt

Defination:
 servlet is a java class that extends the
functionality of web server.
Eg:
 mail server
servlet is a class that performs virus scan to attached files

Benefits
 only one copy of servlet is loaded into jvm.
 each request begins a new thread to servlet process.
◙ save time
◙ response time increases
◙ it is scalable

Servlet implementation:
 servlet use class and interface from 2 package
◘ javax.servlet
 It contains classes to support generic protocol
◘ javax.servlet.http
 It extends classes in servlet package to add HTTP sapecific
functionality.

Servlet API :
o Servlet interface
o Genericservlet class
o HTTPservletrequest interface
o HTTPservletrequest interface
o Cookie class
o HTTPsession interrface
o single threadmodel interface
o servletexception class
o unavailableexception class
o servlettcontext interfave
o serrvletconfig interrface

Servlet interface:
 Every servlet must implements the javax.servlet interface
 It can implement in 2 ways:
◙ Directly implementing interface
◙ Extending any of 2 classes:
◙ javax.serrvlet.genricservlet
◙ javax.servlet.http.HTTPservlet

Methods:
◘ Init()
◘ Service()
◘ Destroy()
◘ Getservletinfo()
◘ Getservletconfig()

Service()
syntax:
 public abstract voidservice(servletrequest req,
servletresponse res)throws
servletException,IOException
◙ it is called whenever the request is made
◙it must be overridden in servlet
◙ it receives request via servletrequest and sends
response via servlet response

HTTP servlet
 It is an abstract class that is used for developing
HTTpservlets.
 It dose not override the service() method.
 It override doget() to handle GET requests and dopost()to
handle POST requests

Methods:
o serrvice()
o doget()
o dopost()
o dodelete()
o dooption()
o do put()
o do trace()

do get() or do post()
o protected void doget(HTTPServletRequest req
HTTPServletResponse res)throws servletException,IOException
o protected void dopost(HTTP ServletRequest
req,HTTPservletresponse res) throws
servletException,IOException

public class SessionServlet extends HttpServlet {
public void doGet(HttpServletRequest req, HttpServletResponse res) throws IOException
{
res.setContentType("text/html");
OutputStream out = res.getOutputStream();
PrintWriter pw = new PrintWriter(new OutputStreamWriter(out));
HttpSession session = req.getSession(false);
if (session == null) {
session=req.getSession(true);
session.putValue ("VisitCount", "1");
}
pw.println("<html><body><pre>");
pw.println("session.isNew()="+session.isNew());
pw.println("session.getCreationTime()="+ new java.util.Date(
session.getCreationTime()));
pw.println("session.getID()="+session.getId());
pw.println("session.getLastAccessedTime()=" + new
java.util.Date(session.getLastAccessedTime()));
String strCount = (String) session.getValue("VisitCount");
pw.println("No. of times visited = " + strCount);
int count = Integer.parseInt(strCount); count++;
session.putValue("VisitCount", Integer.toString(count));
pw.println ("</pre></body></html>");
pw.flush();
}
}

Java ppt

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Java ppt