import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class InitDestroyCounter extends HttpServlet {
int count;
public void init() throws ServletException {
// Try to load the initial count from our saved persistent state
FileReader fileReader = null;
BufferedReader bufferedReader = null;
try {
fileReader = new FileReader("InitDestroyCounter.initial");
bufferedReader = new BufferedReader(fileReader);
String initial = bufferedReader.readLine();
count = Integer.parseInt(initial);
return;
}
catch (FileNotFoundException ignored) { } // no saved state
catch (IOException ignored) { } // problem during read
catch (NumberFormatException ignored) { } // corrupt saved state
finally {
// Make sure to close the file
try {
if (bufferedReader != null) {
bufferedReader.close();
}
}
catch (IOException ignored) { }
}
// No luck with the saved state, check for an init parameter
String initial = getInitParameter("initial");
try {
count = Integer.parseInt(initial);
return;
}
catch (NumberFormatException ignored) { } // null or non-integer value
// Default to an initial count of "0"
count = 0;
}
public void doGet(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException {
res.setContentType("text/plain");
PrintWriter out = res.getWriter();
count++;
out.println("Since the beginning, this servlet has been accessed " +
count + " times.");
}
public void destroy() {
super.destroy(); // entirely optional
saveState();
}
public void saveState() {
// Try to save the accumulated count
FileWriter fileWriter = null;
PrintWriter printWriter = null;
try {
fileWriter = new FileWriter("InitDestroyCounter.initial");
printWriter = new PrintWriter(fileWriter);
printWriter.println(count);
return;
}
catch (IOException e) { // problem during write
// Log the exception. See Chapter 5.
}
finally {
// Make sure to close the file
if (printWriter != null) {
printWriter.close();
}
}
}
}
|