Can anyone please help me here? Basically I have modified the source
code and understood it but when I update a record in the db using a
JSP, it gives me an error "The flight you selected does exist."
Althought there is not selection going on, instead it is entered, I
need it to match the flight in the db using the flightNo. I want all
the attributes to be changed apart from the flightNo itself as it is
it's associated details I need changing (i.e. flightdate, destination,
arrTime and depTime).
Below are the code snippets but did not include everything as all
details were not neded. Therefore I had put part of it. But
somewhere I am going wrong of "updating" a db record.
public class Flight
{
String flightNo;
Date flightDate;
String destination;
Time arrTime;
Time depTime;
Flight(String flightNo, Date flightDate, String destination, Time
arrTime, Time depTime)
{
this.flightNo = flightNo;
this.flightDate = flightDate;
this.destination = destination;
this.arrTime = arrTime;
this.depTime = depTime;
}
public String getFlight()
{
return flightNo;
}
public Date getFlightDate()
{
return flightDate;
}
public String getDestination()
{
return destination;
}
public Time getArrTime()
{
return arrTime;
}
public Time getDepTime()
{
return depTime;
}
public String toString()
{
return flightNo;
}
}
public class FlightService
{
private FlightDAO flightDataAccess;
public FlightService()
{ flightDataAccess = new FlightDAO(); }
public Flight getFlight(String flightNo)
{
Flight flight = null;
try
{
flight = flightDataAccess.retrieve(flightNo);
}
catch (ObjectNotFoundException onfe) { flight = null; }
return flight;
}
public Flight updateFlight(String flightNo, Date flightDate, String
destination, Time depTime, Time arrTime)
{
Flight flight = new Flight(flightNo, flightDate, destination,
depTime, arrTime);
// Perform the DB transaction
flightDataAccess.update(flight);
return flight;
}
}
class FlightDAO
{
FlightDAO() {}
Flight retrieve(String flightNo)
throws ObjectNotFoundException {
// Assume everything is declared
try
{
// Get a database connection
connection = connectionPool.getConnectionNoWait();
// Create SQL SELECT statement
stmt = connection.prepareStatement(RETRIEVE_STMT);
// Initialize statement and execute the query
stmt.setString(1, flightNo);
results = stmt.executeQuery();
// Iterator over the query results
while ( results.next() )
{
// We expect only one row to be returned
num_of_rows++;
if ( num_of_rows > 1 )
{
throw new SQLException("Too many rows were returned.");
}
// Create and fill-in the Flight object
flight = new Flight(results.getString("FlightNo"),
results.getDate("FlightDate"),
results.getString("Destination"),
results.getTime("ArrivalTime"),
results.getTime("DepartureTime"));
}
if ( flight != null ) { return flight; }
else { throw new ObjectNotFoundException(); }
// Handle any SQL errors
}
catch (SQLException se)
{
throw new RuntimeException("A database error occured. " +
se.getMessage());
//Some more catch statements and finally blocks exist.
}
private static final String RETRIEVE_STMT
= "SELECT FlightNo, FlightDate, Destination, ArrivalTime,
DepartureTime FROM Flight WHERE FlightNo = ?";
void update(Flight flight) {
// Assume all declared
PreparedStatement update_stmt = null;
try {
// Get a database connection
connection = connectionPool.getConnectionNoWait();
// Create SQL INSERT statement
update_stmt = connection.prepareStatement(UPDATE_STMT);
// Add data fields
update_stmt.setDate(1, flight.flightDate);
update_stmt.setString(2, flight.destination);
update_stmt.setTime(3, flight.arrTime);
update_stmt.setTime(4, flight.depTime);
// Execute SQL INSERT statement
update_stmt.executeUpdate();
// Handle any SQL errors
}
catch (SQLException se)
{
throw new RuntimeException("A database error occured. " +
se.getMessage());
//Assume catch and finally block exist
}
}
}
private static final String UPDATE_STMT
= "UPDATE Flight SET FlightDate = ?, Destination = ?, ArrivalTime =
?, DepartureTime = ? WHERE FlightNo = ?";
}
//Assume all imports exist
public final class FlightServlet extends HttpServlet
{
public void doPost(HttpServletRequest request,
HttpServletResponse response)
throws IOException, ServletException {
processRequest(request, response);
}
public void processRequest(HttpServletRequest request,
HttpServletResponse response)
throws IOException, ServletException {
// Declare the dispatcher for the View
RequestDispatcher view = null;
// Declare service and database variables
FlightService flightSvc;
Flight flight = null;
// Create the status object and store i tin the request for use
// by the 'Error Page' View (if necessary)
Status status = new Status();
request.setAttribute("status", status);
// Extract HTML form parameters
String flightNo = request.getParameter("flightNo");
String dateString = request.getParameter("flightDate");
Date flightDate = Date.valueOf(dateString);
String destination = request.getParameter("destination");
String timeString = request.getParameter("depTime");
Time depTime = Time.valueOf(timeString + ":00");
String timeStr = request.getParameter("arrTime");
Time arrTime = Time.valueOf(timeStr + ":00");
// Assume there are if-else statements
// Now delegate the real work to the FlightService object
try
{
// Create the "flight service" object
flightSvc = new FlightService();
// Check if this flight object already exists
flight = flightSvc.getFlight(flightNo);
if ( flight != null )
{
status.addException(
new Exception("The flight you selected already exists;"));
}
// If any of the above verification failed, then return the
// 'Update Flight Form' View and return without proceeding with
the
// rest of the business logic
if ( ! status.isSuccessful() ) {
view = request.getRequestDispatcher("updateform.jsp");
view.forward(request, response);
return;
}
// Add the flight to the data-file
flight = flightSvc.updateFlight(flightNo, flightDate,
destination,
depTime, arrTime);
request.setAttribute("flight", flight);
// The flight update process was successful,
// forward to the 'Flight Updated' View
view = request.getRequestDispatcher("thank_you.jsp");
view.forward(request, response);
// Handle any business logic errors
} catch (Exception e) {
status.addException(e);
view = request.getRequestDispatcher("updateform.jsp");
view.forward(request, response);
}
}
}
Can anyone please suggest where to change and what would be the
correct code fragment? I'd be really appreciated. Thanks for your
contribution.
