I have recently started studying java ee applications. One of our tasks for a college project is to build a flight booking system. To do this I am using a number of servlets and a stateful java bean. At the moment the data I'm using is loaded into arrays, later I'll add a database.
It's my understanding that the information in the stateful bean should remain there for the duration of the session, however, I'm loosing an array of data somewhere along the way. I currently have 3 web servlets:
AirportFinder: this provides the user with start and destination airports from the available options based on their search terms.
FlightConfirmation: this provides a list of airlines that fly that route, along with the prices
I currently only have one bean:
The problem arises when I try to confirm the booking. I have created an ArrayList and instantiated it in the constructor of the bean. When the FlightConfrimation servlet passes information back to the SearchFlights bean I add the results to the ArrayList before passing it back to the FlightConfirmation servlet.
Later, I try to access this ArrayList from another method when the BookingConfirmation servlet needs the data, but I keep getting a null pointer exception. When I test the size of the ArrayList when I initially add the data it's correct. But the next time the ArrayList is queried by the BookingConfirmation servlet it has a size of 0. Is my understanding of how a stateful bean is supposed to work incorrect?
Here is my code for the SearchFlights bean:
public class SearchFlights {
String[][] bookedFlights;
String filePath = "C:\\Users\\some path\\Documents\\NetBeansProjects\\FlightFinder\\database_files\\";
BufferedReader reader;
ArrayList<String[]> airports;
ArrayList<String[]> airlines;
ArrayList<String[]> routes;
ArrayList<String[]> routeResults;
public SearchFlights() {
airports = new ArrayList();
airlines = new ArrayList();
routes = new ArrayList();
routeResults = new ArrayList();
try {
reader = new BufferedReader(new FileReader(filePath + "airports.dat"));
while (reader.ready()) {
String row = reader.readLine();
row = row.replaceAll("\"", "");
airports.add(row.split(","));
}
reader = new BufferedReader(new FileReader(filePath + "airlines.dat"));
while (reader.ready()) {
String row = reader.readLine();
row = row.replaceAll("\"", "");
airlines.add(row.split("\\s*,\\s*"));
}
reader = new BufferedReader(new FileReader(filePath + "routes.dat"));
while (reader.ready()) {
String row = reader.readLine();
row = row.replaceAll("\"", "");
routes.add(row.split("\\s*,\\s*"));
routes.get(routes.size() - 1)[7] = String.valueOf((int) (Math.random() * 500));
}
reader.close();
} catch (Exception ex) {
Logger.getLogger(SearchFlights.class.getName()).log(Level.SEVERE, null, ex);
}
}
public String searchDatabase(String from, String to) {
ArrayList<String[]> fromIATA = new ArrayList();
ArrayList<String[]> toIATA = new ArrayList();
int found = 0;
for (String[] airport : airports) {
if (airport[2].toLowerCase().contains(from.toLowerCase())) {
fromIATA.add(airport);
found++;
} else if (airport[2].toLowerCase().contains(to.toLowerCase())) {
toIATA.add(airport);
found++;
}
StringBuilder form = new StringBuilder();
form.append("<h2>Select From:</h2>");
for (int i = 0; i < fromIATA.size(); i++) {
String[] result = fromIATA.get(i);
form.append("<input type=\"radio\" name=\"from\" value=\"").append(result[0]).append("\">")
.append("<b>").append(result[1]).append("</b>")
.append(", ").append(result[2])
.append(", ").append(result[3])
.append(", ").append(result[4])
.append(", ").append(result[5])
.append(", ").append(result[6])
.append(", ").append(result[7])
.append(", ").append(result[8])
.append(", ").append(result[9])
.append("<br>");
}
form.append("<h2>Select To:</h2>");
for (int i = 0; i < toIATA.size(); i++) {
String[] result = toIATA.get(i);
form.append("<input type=\"radio\" name=\"to\" value=\"").append(result[0]).append("\">")
.append("<b>").append(result[1]).append("</b>")
.append(", ").append(result[2])
.append(", ").append(result[3])
.append(", ").append(result[4])
.append(", ").append(result[5])
.append(", ").append(result[6])
.append(", ").append(result[7])
.append(", ").append(result[8])
.append(", ").append(result[9])
.append("<br>");
}
StringBuilder message = new StringBuilder(
"<!DOCTYPE html>"
+ "<html>"
+ "<head>"
+ "<title>Flight Finder Results</title>"
+ "</head>"
+ "<body>"
+ "<h1>Available Flights </h1>"
+ "<form action=\"FlightConfirmation\" method=\"post\">"
+ form.toString()
+ "<input type=\"submit\" value=\"Select Flight\">"
+ "</form>"
+ "</body>"
+ "</html>");
return message.toString();
}
public ArrayList<String[]> findRoutes(String from, String to) {
ArrayList<String[]> validRoutes = new ArrayList();
for (String[] route : routes) {
if (route[3].toLowerCase().equals(from.toLowerCase()) && route[5].toLowerCase().equals(to.toLowerCase())) {
validRoutes.add(route);
routeResults.add(route);
}
}
System.out.println("Results size = " + routeResults.size());
return validRoutes;
}
public ArrayList<String> getAirlineNames(ArrayList<String[]> airlineRoutes) {
ArrayList<String> names = new ArrayList();
for (String[] airline : airlineRoutes) {
for (int i = 0; i < airlines.size(); i++) {
if (airlines.get(i)[3].equals(airline[0])) {
names.add(airlines.get(i)[1]);
}
}
}
return names;
}
public String[] getAirportNames(String from, String to) {
String[] names = new String[2];
for (String[] airport : airports) {
if (airport[0].equals(from)) {
names[0] = airport[1];
} else if (airport[0].equals(to)) {
names[1] = airport[1];
}
}
return names;
}
public String getResultForConfirmaiton(int i) {
StringBuilder form = new StringBuilder();
System.out.println("routeResults called from BookingConfirmation: " + routeResults.size());
String[] result = routeResults.get(i);
String[] airportNames = getAirportNames(result[2], result[4]);
ArrayList<String> airlineNames = getAirlineNames(routeResults);
form.append("<input type=\"radio\" name=\"selectedflight\" value=\"").append("\">")
.append("<b>").append(airlineNames.get(i)).append("</b>")
.append(": ").append(airportNames[0])
.append(" to ").append(airportNames[1])
.append(". Price: ").append(result[7])
.append(".<br>");
return form.toString();
}
}
My understanding was incorrect, I believe the answer is that stateful beans remain active with data through method calls from a single servlet, not throughout the whole user process, so once that servlet is finished with the stateful bean the data is lost.