2. 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
3. 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
4.
5.
6. 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.
7.
8.
9. 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
10. 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
12. 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
13. 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
16. 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
17. 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();
}
}
