booktitlemidlet.java

java web services how to program

// Fig. 14.8: BookTitleMIDlet.java.
// BookTitleMIDlet invokes the Book Titles Web service from a
// servlet to receive a list of book titles.
package com.deitel.jws1.j2me.client;

// import J2ME packages
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;

// import Deitel packages
import com.deitel.jws1.services.BookTitles;

public class BookTitleMIDlet extends MIDlet {

   private Display display; // display manager
   private List mainScreen; // list of available Web services

   private final static int SERVLET = 0;
   private final static int ENHYDRA = 1;

   public BookTitleMIDlet()
   {
      // create main screen with Web-service list
      mainScreen = new List( "Web services", List.IMPLICIT );
      mainScreen.append( "Get Book Titles", null );

      // create soft button commands
      Command selectCommand = 
         new Command( "Select", Command.OK, 0 );
      mainScreen.addCommand( selectCommand );

      // allow soft button access for mainScreen
      mainScreen.setCommandListener(
         new CommandListener() {

            // invoked when user presses soft button
            public void commandAction( 
               Command command, Displayable displayable )
            {
               display.setCurrent( createServiceAccessForm() );
            }
         }
      );

      // get appropriate Display manager for MIDP device
      display = Display.getDisplay( this );
   }

   // start MIDlet and enable user input
   public void startApp()
   {
      // set display to main Screen
      display.setCurrent( mainScreen );
   }

   // pause MIDlet
   public void pauseApp() {}

   // terminate MIDlet lifecycle
   public void destroyApp( boolean unconditional ) {}

   // create Form for selecting how to access Web service
   private Screen createServiceAccessForm()
   {
      Form accessScreen = new Form( "Invoke Web service via:" );

      // ChoiceGroup that enables user to specify means of access
      final ChoiceGroup choices = new ChoiceGroup( "", 
         ChoiceGroup.EXCLUSIVE );
      choices.append( "Servlet", null );
      choices.append( "Enhydra", null );

      // append ChoiceGroup to Form
      accessScreen.append( choices );

      // create soft button commands
      Command invokeCommand = 
         new Command( "Invoke", Command.OK, 0 );
      accessScreen.addCommand( invokeCommand );

      Command backCommand = 
         new Command( "Back", Command.BACK, 1 );
      accessScreen.addCommand( backCommand );

      // allow soft button access for this Screen
      accessScreen.setCommandListener(
         new CommandListener() {

            // invoked when user presses soft button
            public void commandAction( 
               Command command, Displayable displayable )
            {
               // invoke service if user presses SELECT button
               if ( command.getCommandType() == Command.OK ) {

                  BookTitles service = null;

                  // determine means of Web-service access
                  int selection = choices.getSelectedIndex();
                  if ( selection == SERVLET )
                     service = new BookTitleServiceViaServlets();
                  else if ( selection == ENHYDRA )
                     service = new BookTitleServiceViaEnhydra();

                  String titles[] = null;

                  // invoke Web service through interface
                  if ( service != null )
                     titles = service.getBookTitles();

                  // display book titles in List
                  if ( titles != null ) {
                     List titlesScreen = new List( 
                        "Book Titles", List.IMPLICIT );

                     // store book titles in List
                     for ( int i = 0; i < titles.length; i++ )
                        titlesScreen.append( titles[ i ], null );

                     // display List of book titles
                     display.setCurrent( titlesScreen );
                  }

                  // display error page for 3 seconds if error
                  else {
                     Alert errorPage = new Alert( "Error", 
                        "Cannot invoke Web Service", null, 
                        AlertType.ERROR );
                     errorPage.setTimeout( 3000 );
                     display.setCurrent( errorPage );
                  }
               }

               // display mainScreen if user presses BACK button
               else if ( command.getCommandType() == Command.BACK )
                  display.setCurrent( mainScreen );

            } // end method commandAction

         } // end anonymous inner class
      );

      return accessScreen;

   } // end method createServiceAccessForm

} // end class BookTitleMIDlet