ch3.sharedVariable.error
Class Controller

java.lang.Object
  javax.servlet.GenericServlet
      javax.servlet.http.HttpServlet
          ch3.sharedVariable.error.Controller

All Implemented Interfaces:

java.io.Serializable, javax.servlet.Servlet, javax.servlet.ServletConfig

Direct Known Subclasses:

Controller

public class Controller
extends javax.servlet.http.HttpServlet

A controller that increments a member variable. The addition simulates the distinct steps that the CPU would use to add one to a variable.

If the controller is called from two different browsers within three seconds, then both browsers will receive the same value for the incremented variable.

See Also:

Serialized Form

Field Summary

int	accessCount The variable that is being incremented.

Constructor Summary

Controller()

Method Summary

protected void	doGet(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) Handles the HTTP GET method.
void	incrementSharedVariable() Simulate the steps that a CPU performs to increment a variable.

Methods inherited from class javax.servlet.http.HttpServlet

doDelete, doHead, doOptions, doPost, doPut, doTrace, getLastModified, service, service

Methods inherited from class javax.servlet.GenericServlet

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

Methods inherited from class java.lang.Object

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

Field Detail

accessCount

public int accessCount

The variable that is being incremented.

Constructor Detail

Controller

public Controller()

Method Detail

doGet

protected void doGet(javax.servlet.http.HttpServletRequest request,
                     javax.servlet.http.HttpServletResponse response)
              throws javax.servlet.ServletException,
                     java.io.IOException

Handles the HTTP GET method. It always does the same thing: increments a member variable.

Overrides:

doGet in class javax.servlet.http.HttpServlet

Parameters:

request - Request information encapsulated in a Java object

response - Response information encapsulated in a Java object

Throws:

javax.servlet.ServletException

java.io.IOException

incrementSharedVariable

public void incrementSharedVariable()

Simulate the steps that a CPU performs to increment a variable.

1. Copy to a register (temp = accessCount)
2. Increment the register (temp++)
3. Copy back to memory (accessCount = temp)

After the variable is incremented, the thread is put to sleep for three seconds, to simulate that the thread was interrupted by the CPU.