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I will explain the program code in fragments. The first fragment in Listing 1 shows the import directives necessary to support servlet programming.

Listing 1 - Import directives.
import java.io.*; import javax.servlet.*;import javax.servlet.http.*;

The Servlet interface

All servlets must implement the Servlet interface. You can implement it directly. However, it is more common to implement it indirectly by extending a class that implements the interface (such as HttpServlet ).

The Servlet interface declares methods for managing the servlet and its communications with clients. You will need to override some or all of those methods when you write your servlet.

Listing 2 shows the beginning of the controlling class for the servlet. Note that the servlet class extends HttpServlet . By extending the HttpServlet class, the servlet implements the Servlet interface indirectly.

Listing 2 - Beginning of the class definition.
public class Servlet01 extends HttpServlet{

Request and response objects

Two object references are passed to a servlet when it called by a client:

  • ServletRequest - encapsulates the communication from the client to the server.
  • ServletResponse - encapsulates the communication from the servlet back to the client

Access to these objects can be accomplished in more than one way. This servlet overrides the doGet method, which receives references to the two objects as incoming parameters.

The overridden doGet method

The beginning of the overridden doGet method is shown in Listing 3 .

Listing 3 - Beginning of the overridden doGet method.
public void doGet(HttpServletRequest req, HttpServletResponse res)throws ServletException, IOException{

Note that the doGet method throws an exception of type ServletException . In this servlet, some of the code inside the doGet method also throws an IOException , which is not handled inside the method. Thus, it is declared in the method signature.

Browser commands and servlet methods

A Java-enabled server provide a method corresponding to each of the commands that an HTTP client can send to its server. When the server receives a command from the client, the corresponding method is called on the servlet.

As the servlet programmer, you override some or all of those methods to provide the desired behavior.

The doGet method and the HTTP GET command

The doGet method corresponds to the HTTP GET command. If you don't override the method, the default implementation reports an HTTP BAD_REQUEST error when the browser sends a GET command.

Overriding the doGet method to support the GET command also automatically supports the HTTP HEAD command.

(The HEAD command is a GET command that returns no body in the response. It just returns the requested header fields.)

The fundamental purpose of the GET command makes it possible for the client to get something from the server. When you override the doGet method, you should

  • Read data from the request
  • Construct the proper headers in the response
  • Gain access to either the writer or the output stream (depending on whether the material to be returned is text or binary data)
  • Write the response data

Questions & Answers

find the 15th term of the geometric sequince whose first is 18 and last term of 387
Jerwin Reply
The given of f(x=x-2. then what is the value of this f(3) 5f(x+1)
virgelyn Reply
hmm well what is the answer
how do they get the third part x = (32)5/4
kinnecy Reply
can someone help me with some logarithmic and exponential equations.
Jeffrey Reply
sure. what is your question?
okay, so you have 6 raised to the power of 2. what is that part of your answer
I don't understand what the A with approx sign and the boxed x mean
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
I'm not sure why it wrote it the other way
I got X =-6
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
oops. ignore that.
so you not have an equal sign anywhere in the original equation?
is it a question of log
Commplementary angles
Idrissa Reply
im all ears I need to learn
right! what he said ⤴⤴⤴
what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
Kevin Reply
a perfect square v²+2v+_
Dearan Reply
kkk nice
Abdirahman Reply
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
Kim Reply
or infinite solutions?
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Embra Reply
if |A| not equal to 0 and order of A is n prove that adj (adj A = |A|
Nancy Reply
rolling four fair dice and getting an even number an all four dice
ramon Reply
Kristine 2*2*2=8
Bridget Reply
Differences Between Laspeyres and Paasche Indices
Emedobi Reply
No. 7x -4y is simplified from 4x + (3y + 3x) -7y
Mary Reply
how do you translate this in Algebraic Expressions
linda Reply
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
Crystal Reply
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
Chris Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
I'm interested in nanotube
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
what is system testing
what is the application of nanotechnology?
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
anybody can imagine what will be happen after 100 years from now in nano tech world
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
silver nanoparticles could handle the job?
not now but maybe in future only AgNP maybe any other nanomaterials
I'm interested in Nanotube
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
Ali Reply
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
bamidele Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Object-oriented programming (oop) with java. OpenStax CNX. Jun 29, 2016 Download for free at https://legacy.cnx.org/content/col11441/1.201
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