Class SurveyServlet

java.lang.Object
  |
  +--javax.servlet.GenericServlet
        |
        +--javax.servlet.http.HttpServlet
              |
              +--SurveyServlet

public class SurveyServlet

extends javax.servlet.http.HttpServlet

implements javax.servlet.SingleThreadModel

A sample single-threaded servlet that takes input from a form and writes it out to a file. It is single threaded to serialize access to the file. After the results are written to the file, the servlet returns a "thank you" to the user.

You can run the servlet as provided, and only one thread will run a service method at a time. There are no thread synchronization issues with this type of servlet, even though the service method writes to a file. (Writing to a file within a service method requires synchronization in a typical servlet.)

You can also run the servlet without using the single thread model by removing the implements statement. Because the service method does not synchronize access to the file, multiple threads can write to it at the same time. When multiple threads try to write to the file concurrently, the data from one survey does not follow the data from another survey in an orderly fashion.

To see interaction (or lack of interaction) between threads, use at least two browser windows and have them access the servlet as close to simultaneously as possible. Expect correct results (that is, expect no interference between threads) only when the servlet implements the SingleThreadedModel interface.

See Also:

Serialized Form

Constructor Summary

SurveyServlet()

Method Summary

void	doPost(javax.servlet.http.HttpServletRequest req, javax.servlet.http.HttpServletResponse res) Write survey results to output file in response to the POSTed form.
void	init(javax.servlet.ServletConfig config)

Methods inherited from class javax.servlet.http.HttpServlet

doDelete, doGet, doOptions, doPut, doTrace, getLastModified, service, service

Methods inherited from class javax.servlet.GenericServlet

destroy, getInitParameter, getInitParameterNames, getServletConfig, getServletContext, getServletInfo, init, log, log

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

SurveyServlet

public SurveyServlet()

Method Detail

init

public void init(javax.servlet.ServletConfig config)
          throws javax.servlet.ServletException

Overrides:

init in class javax.servlet.GenericServlet

doPost

public void doPost(javax.servlet.http.HttpServletRequest req,
                   javax.servlet.http.HttpServletResponse res)
            throws javax.servlet.ServletException,
                   java.io.IOException

Write survey results to output file in response to the POSTed form. Write a "thank you" to the client.

Overrides:

doPost in class javax.servlet.http.HttpServlet