ch5 writing a server-side web application

• com.vaadin.ui.UI : a HTML component, may be entire web page, or just part of it.
  • static UI.getCurrent() - thread-local, UI for the currently processed request
  • getPage() - get the page for the UI
• Page : represents the web page and the browser window
  • static Page.getCurrent() - page for the currently processed request, = UI.getCurrent().getPage()
• VaadinSession : user session
  • static VaadinSession.getCurrent() obtains the session
• Components :
  • laid out by layout component
  • user interaction causes events
  • Field components are intended for input and haling of data
  • getUI() : note not available in constructor
  • getPage() : note, not available in constructor
• Event and listeners
  • server push is also possible
• Resources
• Themes
• Data binding
  • property - for a field
  • item - for multiple fields to bind to properties of an item
  • container - a collection of multiple items

Building UI

• layout first : new layout; setSizeFull(); this.setContent(new layout);
• components: layout.addComponent(new component)...

Application Architecture

• 4.2.2 Composite components : extend CustomComponent to create custom component
  • this.setCompositionRoot(a layout, with added components...)
  • setSizeFull();
• 4.2.3 View Navigation : Navigator - a view manager, manage view navigation and URI fragment enabling bookmarking, linking, history going back
• Section 11.2 - embedding UI in web pages

Implementing Event / Listeners

• recommended - implement with anonymous class, without need to distinguish event source (because only be used in one place for one source); the component being listened must be declared "final"

Image, downloadable files and other resources

• Image - component
• Flash - Flash component
• BrowserFrame - embeded browser frame
• Embedded - others embedded resources
• Link - provide downloadable files
• StreamResource - dynamically created resource
• RequestHandler - dynamic resource
• Resource interface and classes
  • ConnectorResource
    • FileResource - file in file system
    • ClassResource - class loader
    • StreamResource - can be used to create dynamic image, report, etc
  • ThemeResource
  • ExternalResource

Error handling

• All component has built-in error indicator
  • automatically turned on when validation fails
  • setComponentError() - explicitly set
• System messages - notification indicating major invalidity (most commonly - session timeout)
  • properties : short caption, message, url to redirect after displaying, enabled / disabled
  • can be customized by setting SystemMessagesProvider in VaadinService
• Uncaught Exceptions
  • DefaultErrorHandler handles uncaught exceptions
    • display as component error
  • Custom error handling
    • Implement custom ErrorHandler, or extend DefaultErrorHandler
    • and enable with setErrorHandler() in any components or in VaadinSession object
• Notifications
  • error or information appear briefly
  • static Notification.show()
  • new Notification("bala bala bala", Notification.TYPE_xxx, true/false HTML content).show(Page.getCurrent());
• Application Lifecycle
  • Deploy, undeploy, redeploy, @PreserveOnRefresh... see doc
  • Customizing Vaadin servlet
    • overriding servletInitialized() method
      • first call super.servletInitialized()
      • VaadinService can be obtained with getService();
• User session
  • getSession() with a UI
  • static VaadinSession.getCurrent();
  • handling user session initialization and destruction: see sample code @4.7.3
• Loading a UI
  • when new UI is created, its init() method is called, request is provided to the method
  • custom UI provider - see doc
  • preserving UI on refresh - see doc
• UI expiration
  • client sends keep-alive to keep UI open
  • by default, (heartbeatInterval in servelet) heartbeats interval = 5min
  • DetachEvent is sent to all DetachListeners to the UI when cleanup happens
  • when detach, detach() is called
• Session Expiration
  • kept open by request and heartbeat
  • can be configured
• Session close
  • VaadinSession.close()
  • typically redirect user to another URL by Page.setLocation()
• Deploying an application
  • operation and content organization, see doc
  • web servlet class and annotation - see doc
  • web.xml - see doc
    • servlet API version
    • widget set
  • servlet mapping, map sub-paths
  • production mode (by default, debug mode) - disable debugging features
  • custom UI provider
  • UI heartbeat
  • session timeout
  • push mode
  • cross-site
  • DeploymentConfiguration = VaadinSession.getConfiguration(), obtain configurations