Communication Software Exam 5º Ingeniero de Telecomunicación February 18th Full name: Part I: Theory Exam

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1 Part I: Theory Exam Duration, exam (this year's students): 3 hours () (last year's students): 2 hours 45 minutes Duration, part I: 2 hours, 30 minutes The use of books or notes is not permitted. Reply to each question on a separate sheet of paper. Exercise 1. (1,5 points) Model the following situation in UML. A parachutist jumps out of a plane and is in free fall from that moment. (S)he can then pull the ripcord to open the main parachute. On doing so, two things can happen: either it opens, in which case (s)he shouts "yes!" and starts to fall slowly, or it doesn't open, in which case (s)he remains in free fall. If the main parachute doesn't open, (s)he can try to open the reserve parachute with the same two possible outcomes. If (s)he remains in free fall for longer than max_fall_time (s)he sees her entire life flash by before his/her eyes (this should be modelled using a halucinate() method) and the fall becomes a death fall. In all cases, (s)he eventually reaches the ground. Exercise 2. (1,5 point) Explain the mechanisms by which the Jini system dynamically adapts to new services arriving and old services leaving, without newly-arrived clients or service providers having any prior knowledge of the local Jini federation. Include in your explanation a brief description of the different protocols involved. Exercise 3 (1,5 point) Study the following code (conforming to the EJB 2.0 specification) for a bean class and then answer the questions appearing below it. Note that certain parts of the code have been replaced with XXXX. 1 import javax.ejb.*; 2 import java.rmi.remoteexception; 3 import java.util.*; 4 import asg.services.*; 5 6 public class MusicBean implements XXXXBean { 7 8 CustomerVO customer; 9 ArrayList shoppinglist; // create() methods implementation; initialize state variables public void ejbcreate(string person) throws CreateException { 14 if (person == null person.equals("")) { 15 throw new CreateException("Name null or empty.");

2 16 } 17 else { 18 customer = new CustomerVO(person, "NoPassword", "No "); 19 } 20 shoppinglist = new ArrayList(); 21 } public void ejbcreate(customervo cust) throws CreateException { 24 if (cust.getname() == null) { 25 throw new CreateException("Name cannot be null."); 26 } 27 if (cust.getpasswd()==null cust.getpasswd().equals("")) { 28 throw new CreateException("Password null or empty."); 29 } 30 if (cust.get () == null cust.get ().equals("")) { 31 throw new CreateException(" null or empty."); 32 } 33 customer = cust; 34 shoppinglist = new ArrayList(); 35 } public CustomerVO getcustomer() { 38 return customer; 39 } public void addrecording(recordingvo album) { 42 shoppinglist.add(album); 43 } // ShoppingException is an application exception 46 public void removerecording(recordingvo album) 47 throws ShoppingException 48 { 49 if (shoppinglist.contains(album)) { 50 shoppinglist.remove(shoppinglist.indexof(album)); 51 } 52 else { 53 throw new ShoppingException(album.getTitle() 54 + " not in cart."); 55 } 56 } // clear the shopping list 59 public void clearshoppinglist() { 60 shoppinglist.clear(); 61 } public ArrayList getshoppinglist() { 64 return shoppinglist; 65 } public MusicBean() {} 68 public void ejbremove() {} 69 public void ejbactivate() {} 70 public void ejbpassivate() {} 71 public void setxxxxcontext(xxxxcontext sc) {} } // MusicBean

3 (a) What type of EJB is being coded here? Give as much information as you can and justify your answer. (b) What can you say about the last five methods of this class? (c) Assuming there are no local interfaces, what form will the code for the interfaces of this EJB take? Exercise 4 (2 points) (a) (0,5 points) Describe the correspondence between SQL-DML statements and relational algebra operations. (b) (1,5 point) Suppose that a large family uses a database to manage their childrens' extracurricula activities and that the database contains the following tables: ACTIVITIES Activity_Code Activity_Name Place Day Start_Time Finish_Time Equipment CHILDREN Child_Code Child_Name Age CHILDREN-ACTIVITY Child_Code Activity_Code Start_Date Finish_Date Each activity takes place once a week and always on the same day of the week. The date that a child is to stop doing an activity may be unknown, in which case the Finish_Date field has the value 0. When a child stops doing an activity, the Finish_Date field is updated with the current date. You may suppose that dates can be directly compared and that, in the date format used, May 1 st 2006, for example, is written Now give the SQL sentences that implement the following instructions: (i) (ii) (iii) List the times and places at which a child will need to be collected (after an activity) on Thursday May 5 th 2006 (together with the name of the child). Modify the Finish_Date of all the activities which the youngest child is currently doing by setting it to today's date. You may use the set function MIN(). List the names of the children (without repetition!) that need a towel (equipment) at least once a week between Monday March 6 th 2006 and Friday March 24 th You may suppose that the Equipment field never contains more than one item of equipment. (iv) Delete from the database all those activities that no child is doing since Jan 1 st 2006.

4 Exercise 5. (3,5 points) Suppose we wish to implement an application for buying tickets to different events (music, cinema, sports, etc.) on the Internet using Servlets and JSPs. The system should be designed as a wizard split over three pages, together with a confirmation page: 1. The main page (index.html or index.jsp) shows the general information for the event: topic place time price per person. This information is static. This page has one button Next, to proceed to the next page. 2. The page for introducing the personal data: first and last names (of type String) address (a String of at least 9 characters containing character and after it the. character) the number of accompanying persons (of type int, with values between 0 and 9). This page has two buttons: Back, to go to the previous page, and Next, to proceed to the next page. 3. The Page for introducing the payment data: type of credit card ( Visa or Mastercard ) credit card number (16 digits, of type long) expiry date: year (2 digits, of type int) and month (an int in range 1 to 12). This page should show the total amount due, which depends on the price per person and the number of attendees. It has two buttons: Back, to go to the previous page, and Done, to finish the reservation. 4. A confirmation page containing all the data, to be shown when the reservation is completed. This page has no buttons. It should be taken into account that: When using the Back and Next buttons between pages, the contents of the corresponding forms should be maintained. The input data should be checked. Only when no field is empty and all the data is correct, can the user proceed to the next page. Otherwise, the previous page should be shown, with an explanatory error message. When going back to a previous page from a (partially) filled page, it is not necessary to check the data, but it should be adequately stored. For this simplified example, it is not necessary to save data permanently in a database.

5 The system is to use 3 JavaBeans: 1. The first is a RegistrationBean; in this bean, the user data is saved alter being validated. The properties of this bean are as follows: String firstname; String lastname; String ; int accompanying_persons; String creditcard; long creditcardnumber; int expiryyear; int expirymonth; 2. The second is a RegistrationViewBean, in this bean, unvalidated user data is stored and in which this data is validated. Its properties are the same as those of the previous bean. It also has the methods: Hashtable checkpersonaldataandinitregistrationbean(registrationbean b); Checks if the personal data in RegistrationViewBean are correct. If so, it is stored in the corresponding property of the parameter RegistrationBean. If not, it is stored as an error in the returned hash table. Hashtable checkpaymentdataandinitregistrationbean(registrationbean b); The same for the payment data. Hashtable checkdataandinitregistrationbean(registrationbean b); The same for all the data (calls the 2 previous methods). 3. Finally, the third is a Hashtable, where the errors that have been detected are stored. The most relevant methods of a hash table are the following: void clear(); // clears the table Object put(object key, Object value); //inserts a key/value pair void putall(map t); // inserts contents of another table boolean containskey(object key); // true if key is in table Object get(object key); //returns value corresponding to key boolean isempty(); // true if table is empty (a) (1 Point) The following JSP is that used to introduce the personal data. You are required to: Describe the functionality of this page in detail Indicate the predefined variables used in this code (give only the names). Identify (with the line number) and classify exactly all the JSP labels that you find. You may wish to group them by type. 1 <%@page contenttype="text/html"%> 2 <html> 3 <head><title>jsp Page</title></head> 4 <body> 5 6 <jsp:usebean id="data" scope="session" 7 class="beans.registrationbean" /> 8 <jsp:usebean id="viewdata" scope="session" 9 class="beans.registrationviewbean" /> 10 <jsp:usebean id="errors" scope="session" 11 class="java.util.hashtable" /> 12

6 13 <form action="checkpersdata.jsp" method="post"> 14 <h1>please introduce your personal data</h1> 15 <table> 16 <tr> 17 <td valign=top>first name: </td> 18 <td><input type ="text" name="firstname" size="30" 19 maxlength="50" value="<%= viewdata.getfirstname() %>"> 20 <% if(errors.containskey("firstname")) 21 out.println("<font color=red>" + errors.get("firstname") 22 + "</font>"); %></td> 23 </tr> 24 <tr> 25 <td>last name: </td> 26 <td><input type ="text" name="lastname" size="30" maxlength="50" 27 value="<%= viewdata.getlastname() %>"> 28 <% if(errors.containskey("lastname")) 29 out.println("<font color=red>" + errors.get("lastname") 30 + "</font>"); %></td> 31 </tr> 32 <tr> 33 <td> </td> 34 <td><input type ="text" name=" " size="30" maxlength="50" 35 value="<%= viewdata.get () %>"> 36 <% if(errors.containskey(" ")) 37 out.println("<font color=red>" + errors.get(" ") 38 + "</font>"); %></td> 39 </tr> 40 <tr> 41 <td>additional participants: </td> 42 <td><input type = "text" name="accompanying" size=30 43 maxlength="50" 44 value="<%= viewdata.getaccompanying() %>"> 45 <% if(errors.containskey("accompanying")) 46 out.println("<font color=red>" + errors.get("accompanying") 47 + "</font>"); %></td> 48 </tr> 49 <tr> 50 <th colspan=2> 51 <input type="submit" name="back" value="back"> 52 <input type="submit" name="next" value="next"> 53 </th> 54 </tr> 55 </table> 56 </form> 57 </body> 58 </html>

7 (b) (1,5 Points) The form in the code of the previous part points to the page checkpersdata.jsp, whose code is as follows: 1 <%@page contenttype="text/html"%> 2 <html><head></head> 3 <body> 4 <jsp:usebean id="data" scope="session" 5 class="beans.registrationbean" /> 6 <jsp:usebean id="viewdata" scope="session" 7 class="beans.registrationviewbean" /> 8 <jsp:usebean id="errors" scope="session" 9 class="java.util.hashtable" /> <jsp:setproperty name="viewdata" property="*" /> <% if(request.getparameter("back")!= null) { 14 %><jsp:forward page="index.jsp" /><% 15 } else { //assume "next" 16 errors.clear(); 17 errors.putall( 18 viewdata.checkpersonaldataandinitregistrationbean(data)); 19 if(errors.isempty()) { 20 %><jsp:forward page="paymentdata.jsp" /><% 21 } else { 22 %><jsp:forward page="persdata.jsp" /><% 23 } 24 } 25 %> 26 </body> 27 </html> Now answer the following questions: (i) With respect to the MVC (Model-View-Controller) architecture, to which of the three categories does this component belong? (ii) Re-write this component as a servlet. (c) (1 Point) Sketch a design of this application, showing the JSPs, servlets (if you wish to use them) and the JavaBeans described above. (Correct) use of UML diagrams will be valued. If you wanted to store in a database the results of correct registration for an event, where in the application would you do this?