// From "Big Java" (1st edition) by Cay Horstmann, Wiley & Sons // Chapter 25 import java.io.PrintWriter; import java.io.IOException; import java.text.DateFormat; import java.util.Date; import java.util.TimeZone; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** This servlet prints out the current local time. The city name must be posted as value of the "city" parameter. */ public class TimeZoneServlet extends HttpServlet { public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // Get information String cityName = request.getParameter("city"); TimeZone zone = getTimeZone(cityName); // Set content type to HTML response.setContentType("text/html"); // Print formatted information PrintWriter out = response.getWriter(); String title = "Time Zone Servlet"; out.println(""); out.println(title); out.println("

"); out.print(title); out.println("

"); if (zone == null) out.println("Sorry--unknown city"); else { out.print("The current time in "); out.print(cityName); out.print(" is: "); DateFormat formatter = DateFormat.getTimeInstance(); formatter.setTimeZone(zone); Date now = new Date(); out.print(formatter.format(now)); } out.println("

"); out.close(); } /** Looks up the time zone for a city @param aCity the city for which to find the time zone @return the time zone or null if no match is found */ private static TimeZone getTimeZone(String city) { String[] ids = TimeZone.getAvailableIDs(); for (int i = 0; i < ids.length; i++) if (timeZoneIDmatch(ids[i], city)) return TimeZone.getTimeZone(ids[i]); return null; } /** Checks whether a time zone ID matches a city @param id the time zone ID (e.g. "America/Los_Angeles") @param aCity the city to match (e.g. "Los Angeles") @return true if the ID and city match */ private static boolean timeZoneIDmatch(String id, String city) { String idCity = id.substring(id.indexOf('/') + 1); return idCity.replace('_', ' ').equals(city); } }