95-702 Organizational Communication and Distributed Object Technologies

January 2009

Homework 1             Due: Friday, May 29 11:59:59 PM 
==========             ================================

       In each part, documentation is required. The software that
       you write (HTML files, Java files and so on) must contain
       comments that describe what each significant piece of code 
       is intended to accomplish. Points will be deducted if code
       is not well documented.

       For each of the three exercises below, submit a documented
       servlet an index.jsp page. The 
       documentation will include your name, a description of 
       each piece of code and well-chosen variable names. In
       addition, you must submit screenshots that demonstrate 
       your programs running.  

    1. Write an index.jsp page that requests a user's name and 
       provides a submit button. When the submit button is pressed 
       a servlet is executed. The servlet sends 400 hello messages
       back to the browser. Each hello message appears on its own
       line and contains the user's name. For example, if the user
       enters Richard and hits the submit button, the output will
       look as follows:

                     Hello Richard
                     Hello Richard
                     :
                     :

       Good Documentation 4 Points
       Works Properly    29 Points

    2. A user can trick this servlet so that it behaves in an unintended 
       manner. For example, a user might enter HTML code into the input
       field. If the input field contains the string "<i>Amy</i>" then
       Amy's name will be echoed back to the browser and displayed in
       italics. Write code in the servlet that prevents any use of 
       anlgle brackets in the user input. Note: a complete answer
       for question 2 does not count for question 1. Question 1 must
       be completed separately.

       The way that you will solve this problem is to use the 
       contains method of the String class. If a left or right
       bracket ("<" or ">") appears in the input replace the input
       string with the value "illegal characters in input". Send this
       string back to the browser. 

       For example, if the user enters <i>Richard</i> and hits the submit     
       button, the output will look as follows:

                     Hello illegal characters in input
                     Hello illegal characters in input
                     :
                     :




       Good Documentation 4 Points
       Works Properly    29 Points

   
    3. Write a simple web application that allows a user 
       to perform one of three operations on two, possibly 
       very large, integers. The operations will include 
       addition and multiplication as well as an operation 
       to determine if the two integers are relatively prime. 

       A JSP page will present three input fields to 
       the user. The first two will be used to collect the two 
       integers. The third will be used to collect the operation 
       type. The only operations supported will be "add", "multiply", 
       and "relativelyPrime".  
       
       A submit button will be provided and when it is hit
       a servlet will be visited. The servlet will use the 
       BigInteger class to perform the conversions from strings 
       and the appropriate computation. The servlet will return 
       the result to the browser marked up in HTML. You need
       to validate both integers and the operation. In the case
       of invalid input return an error message to the browser 
       but don't crash the server.

       The BigInteger class has multiply and add methods that
       will be used by the first two operations. For the operation
       that determines if the two integers are relatively 
       prime use the gcd() method of the BigInteger class. If
       the greatest common divisor of the two integers is one
       then the two integers are relatively prime.


       Good Documentation 4 Points
       Works Properly    25 Points
       Screenshots provided 3 Points