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(The same is true if you put this address into a simple hyperlink when creating a web page.)

If you want to manually enter an address into the address field and cause the doPost method to be called, you must find some other way to do it.

Arguments

Each of the methods requires two arguments. The first, a reference to an HttpServletRequest object, encapsulates the data from the client. The second, a reference to an HttpServletResponse object encapsulates the response to the client.

The HttpServletRequest object provides a large number of methods that the servlet can use to obtain information about the request.

Similarly, the HttpServletResponse object provides a large number of methods that the servlet can use to return data to the client.

The init and destroy methods

You may also find that you need to override the init and destroy methods in your servlet. Recall that each of these methods is called only once. The init method is called when the server loads the servlet class. The destroy method is called when the server removes the servlet class.

Overriding the init method

The servlet should use the init method to prepare the resources it manages and to make the servlet ready to handle client requests. It can do this without regard for multi-threading issues because it is guaranteed that there is only a single thread running during initialization. If the init method is unable to run to a successful completion, it should throw an UnavailableException object.

The init method receives a ServletConfig object as a parameter. For reasons that I won't bother to discuss here, the overridden init method should call super.init and pass this configuration object as a parameter. If you are curious as to the reasons, you can look it up in the documentation.

Overriding the destroy method

Overriding the destroy method is more problematic, particularly if it is necessary to deal with resources that may be shared by service threads that are still running when the server decides to remove the servlet and call its destroy method. I'm going to punt on this one, and suggest that if you find yourself in this situation, you should find a good bookwith an example similar to your situation and use that example for guidance.

The getServletInfo method

Some applications may want to display information about a servlet, such as a short description of the purpose of the servlet, its author, and perhaps its version number. The Servlet API provides a method named getServletInfo to return this kind of information about the servlet. By default, this method returns null. You can override this method to return a String containing information about your servlet.

What's next?

The next module in the series will take on forms and databases.

Miscellaneous

This section contains a variety of miscellaneous information.

Housekeeping material
  • Module name: Java4535: Introduction to Servlet Code
  • File: Java4535.htm
  • Published: 12/20/13
  • Revised: 01/31/16
Disclaimers:

Financial : Although the Connexions site makes it possible for you to download a PDF file for thismodule at no charge, and also makes it possible for you to purchase a pre-printed version of the PDF file, you should beaware that some of the HTML elements in this module may not translate well into PDF.

I also want you to know that, I receive no financial compensation from the Connexions website even if you purchase the PDF version of the module.

In the past, unknown individuals have copied my modules from cnx.org, converted them to Kindle books, and placed them for sale on Amazon.com showing me as the author. Ineither receive compensation for those sales nor do I know who does receive compensation. If you purchase such a book, please beaware that it is a copy of a module that is freely available on cnx.org and that it was made and published withoutmy prior knowledge.

Affiliation : I am a professor of Computer Information Technology at Austin Community College in Austin, TX.

Complete program listing

Listing 6 - Servlet01.java.
/*File Servlet01.java, Copyright 1999, R.G.Baldwin The purpose of this program is to illustrate a verysimple servlet. The servlet produces the following text in the browserwindow in large red letters. Hello Big Red World**********************************************************/ import java.io.*;import javax.servlet.*; import javax.servlet.http.*;public class Servlet01 extends HttpServlet{ public void doGet(HttpServletRequest req, HttpServletResponse res)throws ServletException, IOException{ //Establish the type of outputres.setContentType("text/html");//Get an output stream PrintWriter out = res.getWriter();//Construct an html page to return to the clientout.println("<html>"); out.println("<head><title>Servlet01</title></head>"); out.println("<body>");out.println("<h1 align=\"center\">" +"<font color=\"#FF0000\">"); out.println("Hello Big Red World");out.println("</font></h1>"); out.println("</body></html>"); }//end doGet()}//end class Servlet01

-end-

Questions & Answers

what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
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