Java tutorial
package com.connoisseur.menuapp.client; import com.google.gwt.event.dom.client.ClickEvent; import com.google.gwt.event.dom.client.ClickHandler; import com.google.gwt.event.dom.client.KeyCodes; import com.google.gwt.event.dom.client.KeyUpEvent; import com.google.gwt.event.dom.client.KeyUpHandler; import com.google.gwt.storage.client.Storage; import com.google.gwt.user.client.ui.Button; import com.google.gwt.user.client.ui.DialogBox; import com.google.gwt.user.client.ui.HTML; import com.google.gwt.user.client.ui.HorizontalPanel; import com.google.gwt.user.client.ui.Label; import com.google.gwt.user.client.ui.TextBox; import com.google.gwt.user.client.ui.VerticalPanel; /** The Authenticate Class ** * * This authenticator provides the ability to interact with the menu app upon * successful authentication. The Viewer is mounted after authenticating. * */ public class Authenticate { /** Local storage for saving strings, which persist when the app is shut down. */ private static final Storage storage = StorageContainer.getStorage(); /** This is essentially the main method for the menu app. */ public static void go() { storage.clear(); // uncomment to completely reset app final DialogBox startupBox = new DialogBox(); // movable box that contains widgets startupBox.setAnimationEnabled(true); final VerticalPanel startupPanel = new VerticalPanel(); // can contain other widgets startupPanel.addStyleName("marginPanel"); // interacts with Menuapp.css startupPanel.setHorizontalAlignment(VerticalPanel.ALIGN_CENTER); // check to see if storage is supported if (storage != null) { // load viewer if license key and restID have been submitted before if (storage.getLength() > 0) { Viewer.loadViewer(); } // otherwise load authentication UI in order to receive input else { final Button submitButton = new Button("Submit"); // "Submit" appears on button submitButton.addStyleName("myButton"); // interacts with Menuapp.css final HorizontalPanel buttonPanel = new HorizontalPanel(); // used to center button buttonPanel.addStyleName("marginlessPanel"); // license widgets final Label licenseErrorLabel = new Label(); // dynamic text licenseErrorLabel.addStyleName("errorLabel"); // interacts with Menuapp.css final TextBox submitLicense = new TextBox(); // user can input text using this submitLicense.setText("license key..."); // default text to be seen on load // restaurant ID widgets final Label restErrorLabel = new Label(); restErrorLabel.addStyleName("errorLabel"); final TextBox submitRestID = new TextBox(); submitRestID.setText("restaurant ID..."); // organize UI startupPanel.add(new HTML("Please enter your license key:")); startupPanel.add(submitLicense); startupPanel.add(licenseErrorLabel); startupPanel.add(new HTML("<br>Please enter your restaurant ID:")); startupPanel.add(submitRestID); startupPanel.add(restErrorLabel); startupPanel.add(new HTML("<br>")); buttonPanel.add(submitButton); startupPanel.add(buttonPanel); // setup startupBox, which is what will be seen by the user startupBox.setWidget(startupPanel); // connects the two widgets startupBox.center(); // also shows the box // focus the cursor on submitLicense when startupBox appears submitLicense.setFocus(true); submitLicense.selectAll(); // create a handler for submitButton, submitLicense and submitRestID class MyHandler implements ClickHandler, KeyUpHandler { /** Fired when the user clicks submit. */ public void onClick(ClickEvent event) { submit(); } /** Fired when the user presses Enter in a submit field. */ public void onKeyUp(KeyUpEvent event) { if (event.getNativeKeyCode() == KeyCodes.KEY_ENTER) submit(); } /** Checks the submitted license key and restaurant ID for validity. Loads Viewer if valid. */ private void submit() { String license = submitLicense.getText(); // unused for now String restID = submitRestID.getText(); // not sure how to validate yet int returnFlag = 0; // so that both tests can be done licenseErrorLabel.setText(""); restErrorLabel.setText(""); // validate license String result = FieldVerifier.isValidLicenseKey(license); // from FieldVerifier.java if (!result.equals("")) { // error licenseErrorLabel.setText("You submitted an invalid license key."); submitLicense.selectAll(); returnFlag = 1; } // validate restID result = FieldVerifier.isValidRestaurantID(restID); if (!result.equals("")) { // error restErrorLabel.setText("You submitted an invalid restaurant ID."); submitRestID.selectAll(); returnFlag = 1; } // don't do anything until the errors are resolved if (returnFlag == 1) return; // clean up submitButton.setEnabled(false); submitLicense.setEnabled(false); submitRestID.setEnabled(false); startupBox.hide(); // set up storage storage.setItem("license", license); // secret key for security storage.setItem("restID", restID); // used for almost every call to the backend // show menu Viewer.loadViewer(); } } // MyHandler // attach the handler final MyHandler handler = new MyHandler(); submitButton.addClickHandler(handler); submitLicense.addKeyUpHandler(handler); submitRestID.addKeyUpHandler(handler); } // else load authentication UI } // if storage supported // storage is not supported, so report error else { startupPanel.add(new HTML("<font color=red>The app will not function because local<br>" + "storage is not supported on this platform.</font>")); startupBox.setWidget(startupPanel); startupBox.center(); } } // end go } // Authenticate