Class WApplication


public class WApplication extends WObject
Represents an application instance for a single session.

Each user session of your application has a corresponding WApplication instance. You need to create a new instance and return it as the result of WtServlet.createApplication(WEnvironment). The instance is the main entry point to session information, and holds a reference to the getRoot() of the widget tree.

The recipe for a JWt web application, which allocates new WApplication instances for every user visiting the application is thus:

 public class HelloServlet extends WtServlet {
 public HelloServlet() {

 public WApplication createApplication(WEnvironment env) {
 // In practice, you will specialize WApplication and simply
 // return a new instance.
 WApplication app = new WApplication(env);
 app.getRoot().addWidget(new WText("Hello world."));
 return app;


Throughout the session, the instance is available through the static method getInstance(), which uses thread-specific storage to keep track of the current session. The application may be exited either using the method quit(), or because of a timeout after the user has closed the window, but not because the user does not interact: keep-alive messages in the background will keep the session around as long as the user has the page opened.

The WApplication object provides access to session-wide settings, including:

  • Constructor Details

    • WApplication

      public WApplication(WEnvironment env)
      Creates a new application instance.

      The environment provides information on the initial request, user agent, and deployment-related information.

  • Method Details

    • getInstance

      public static WApplication getInstance()
      Returns the current application instance.

      This method uses thread-specific storage to fetch the current session.

    • getEnvironment

      public WEnvironment getEnvironment()
      Returns the environment information.

      This method returns the environment object that was used when constructing the application. The environment provides information on the initial request, user agent, and deployment-related information.

      See Also:
    • getRoot

      public WContainerWidget getRoot()
      Returns the root container.

      This is the top-level widget container of the application, and corresponds to entire browser window. The user interface of your application is represented by the content of this container.

      The getRoot() widget is only defined when the application manages the entire window. When deployed as a EntryPointType.WidgetSet application, there is no root() container, and null is returned. Instead, use bindWidget() to bind one or more root widgets to existing HTML <div> (or other) elements on the page.

    • findWidget

      public WWidget findWidget(String name)
      Finds a widget by name.

      This finds a widget in the application's widget hierarchy. It does not only consider widgets in the getRoot(), but also widgets that are placed outside this root, such as in dialogs, or other "roots" such as all the bound widgets in a widgetset application.

      See Also:
    • getStyleSheet

      public WCssStyleSheet getStyleSheet()
      Returns a reference to the inline style sheet.

      Widgets may allow configuration of their look and feel through style classes. These may be defined in this inline stylesheet, or in external style sheets.

      It is usually preferable to use external stylesheets (and consider more accessible). Still, the internal stylesheet has as benefit that style rules may be dynamically updated, and it is easier to manage logistically.

      See Also:
    • useStyleSheet

      public void useStyleSheet(WLink link, String media)
      Adds an external style sheet.

      The link is a link to a stylesheet.

      The media indicates the CSS media to which this stylesheet applies. This may be a comma separated list of media. The default value is "all" indicating all media.

      This is an overloaded method for convenience, equivalent to:

       useStyleSheet(Wt::WCssStyleSheet(link, media))
    • useStyleSheet

      public final void useStyleSheet(WLink link)
      Adds an external style sheet.

      Calls useStyleSheet(link, "all")

    • useStyleSheet

      public void useStyleSheet(WLink link, String condition, String media)
      Conditionally adds an external style sheet.

      This is an overloaded method for convenience, equivalent to:

       useStyleSheet(Wt::WLinkedCssStyleSheet(link, media), condition)
    • useStyleSheet

      public void useStyleSheet(WLinkedCssStyleSheet styleSheet, String condition)
      Adds an external stylesheet.

      Widgets may allow configuration of their look and feel through style classes. These may be defined in an inline stylesheet, or in external style sheets.

      External stylesheets are inserted after the internal style sheet, and can therefore override default styles set by widgets in the internal style sheet. External stylesheets must have valid link.

      If not empty, condition is a string that is used to apply the stylesheet to specific versions of IE. Only a limited subset of the IE conditional comments syntax is supported (since these are in fact interpreted server-side instead of client-side). Examples are:

      • "IE gte 6": only for IE version 6 or later.
      • "!IE gte 6": only for IE versions prior to IE6.
      • "IE lte 7": only for IE versions prior to IE7.

      See Also:
    • useStyleSheet

      public final void useStyleSheet(WLinkedCssStyleSheet styleSheet)
      Adds an external stylesheet.

      Calls useStyleSheet(styleSheet, "")

    • removeStyleSheet

      public void removeStyleSheet(WLink link)
      Removes an external stylesheet.

      See Also:
    • setTheme

      public void setTheme(WTheme theme)
      Sets the theme.

      The theme provides the look and feel of several built-in widgets, using CSS style rules. Rules for each theme are defined in the resources/themes/theme/ folder.

      The default theme is "default" CSS theme.

    • getTheme

      public WTheme getTheme()
      Returns the theme.
    • setCssTheme

      public void setCssTheme(String theme)
      Sets a CSS theme.

      This sets a WCssTheme as theme.

      The theme provides the look and feel of several built-in widgets, using CSS style rules. Rules for each CSS theme are defined in the resources/themes/name/ folder.

      The default theme is "default". Setting an empty theme "" will result in a stub CSS theme that does not load any stylesheets.

    • setLayoutDirection

      public void setLayoutDirection(LayoutDirection direction)
      Sets the layout direction.

      The default direction is LayoutDirection.LeftToRight.

      This sets the language text direction, which by itself sets the default text alignment and reverse the column orders of <table> elements.

      In addition, JWt will take this setting into account in WTextEdit, WTableView and WTreeView (so that columns are reverted), and swap the behaviour of WWidget#setFloatSide() and WWidget#setOffsets() for LayoutDirection.RightToLeft languages. Note that CSS settings themselves are not affected by this setting, and thus for example "float: right" will move a box to the right, irrespective of the layout direction.

      The library sets "Wt-ltr" or "Wt-rtl" as style classes for the document body. You may use this if to override certain style rules for a Right-to-Left document.

      The only valid values are LayoutDirection.LeftToRight or LayoutDirection.RightToLeft.

      For example:

       body        .sidebar { float: right; }
       body.Wt-rtl .sidebar { float: left; }

      Note: The layout direction can be set only at application startup and does not have the effect of rerendering the entire UI.

    • getLayoutDirection

      public LayoutDirection getLayoutDirection()
      Returns the layout direction.

      See Also:
    • setBodyClass

      public void setBodyClass(String styleClass)
      Sets a style class to the entire page <body>.

      See Also:
    • getBodyClass

      public String getBodyClass()
      Returns the style class set for the entire page <body>.

      See Also:
    • setHtmlClass

      public void setHtmlClass(String styleClass)
      Sets a style class to the entire page <html>.

      See Also:
    • getHtmlClass

      public String getHtmlClass()
      Returns the style class set for the entire page <html>.

      See Also:
    • setHtmlAttribute

      public void setHtmlAttribute(String name, String value)
      Sets an attribute for the entire page <html> element.

      This allows you to set any of the global attributes (see: on the <html> tag. As well as any tags specific to that tag (see:

      Note: If the value contains more complex JavaScript, make sure that " and ' are properly escaped. Otherwise you may encounter JavaScript errors.

      Note: This can control the <html>'s class, dir , and lang as well, but this should generally be avoided, since the application manages that separately.

      See Also:
    • getHtmlAttribute

      public WString getHtmlAttribute(String name)
      Returns the current <html> element attribute value of the specified name.

      See Also:
    • setBodyAttribute

      public void setBodyAttribute(String name, String value)
      Sets an attribute for the entire page <body> element.

      This allows you to set any of the global attributes (see: on the <body> tag. As well as any tags specific to that tag (see:

      Note: If the value contains more complex JavaScript, make sure that " and ' are properly escaped. Otherwise you may encounter JavaScript errors.

      See Also:
    • getBodyAttribute

      public WString getBodyAttribute(String name)
      Returns the current <body> element attribute value of the specified name.

      See Also:
    • setTitle

      public void setTitle(CharSequence title)
      Sets the window title.

      Sets the browser window title to title.

      The default title is "".

      See Also:
    • getTitle

      public WString getTitle()
      Returns the window title.

      See Also:
    • getCloseMessage

      public WString getCloseMessage()
      Returns the close message.

      See Also:
    • getLocalizedStrings

      public WLocalizedStrings getLocalizedStrings()
      Returns the resource object that provides localized strings.

      This returns the object previously set using setLocalizedStrings().

      WString#tr() is used to create localized strings, whose localized translation is looked up through this object, using a key.

      See Also:
    • getBuiltinLocalizedStrings

      public WXmlLocalizedStrings getBuiltinLocalizedStrings()
      Accesses the built-in resource bundle.

      This is an internal function and should not be called directly.

      See Also:
    • setLocalizedStrings

      public void setLocalizedStrings(WLocalizedStrings translator)
      Sets the resource object that provides localized strings.

      The translator resolves localized strings within the current application locale.

      See Also:
    • setLocale

      public void setLocale(Locale locale)
      Changes the locale.

      The locale is used by the localized strings resource to resolve localized strings.

      By passing an empty locale, the default locale is chosen.

      When the locale is changed, refresh() is called, which will resolve the strings of the current user-interface in the new locale.

      At construction, the locale is copied from the environment (WEnvironment.getLocale()), and this is the locale that was configured by the user in his browser preferences, and passed using an HTTP request header.

      See Also:
    • getLocale

      public Locale getLocale()
      Returns the current locale.

      See Also:
    • refresh

      public void refresh()
      Refreshes the application.

      This lets the application refresh its data, including strings from message resource bundles. This is done by propagating WWidget.refresh() through the widget hierarchy.

      This method is also called when the user hits the refresh (or reload) button, if this can be caught within the current session.

      The reload button may only be caught when cookies for session tracking are configured in the servlet container.

      See Also:
    • bindWidget

      public void bindWidget(WWidget widget, String domId)
      Binds a top-level widget for a EntryPointType.WidgetSet deployment.

      This method binds a widget to an existing element with DOM id domId on the page. The element type should correspond with the widget type (e.g. it should be a <div> for a WContainerWidget, or a <table> for a WTable).

      See Also:
    • url

      public String url(String internalPath)
      Returns a URL for the current session.

      Returns the (relative) URL for this application session (including the session ID if necessary). The URL includes the full application path, and is expanded by the browser into a full URL.

      For example, for an application deployed at

      this method might return "/stuff/app.wt?wtd=AbCdEf". Additional query parameters can be appended in the form of "&param1=value&param2=value" .

      To obtain a URL that is suitable for bookmarking the current application state, to be used across sessions, use getBookmarkUrl() instead.

      See Also:
    • url

      public final String url()
      Returns a URL for the current session.

      Returns url("")

    • makeAbsoluteUrl

      public String makeAbsoluteUrl(String url)
      Makes an absolute URL.

      Returns an absolute URL for a given (relative url) by including the schema, hostname, and deployment path.

      If url is "", then the absolute base URL is returned. This is the absolute URL at which the application is deployed, up to the last '/'.

      The default implementation is not complete: it does not handle relative URL path segments with '..'. It just handles the cases that are necessary for JWt.

      This is not used in the library, except when a public URL is needed, e.g. for inclusion in an email.

      You may want to reimplement this method when the application is hosted behind a reverse proxy or in general the public URL of the application cannot be guessed correctly by the application.

    • resolveRelativeUrl

      public String resolveRelativeUrl(String url)
      "Resolves" a relative URL taking into account internal paths.

      This resolves the relative URL against the base path of the application, so that it will point to the correct path regardless of the current internal path, e.g. if the application is deployed at and we're at the internal path /two/ , so that the full URL is, the output of the input URL three will point to, and not

      If the given url is the empty string, the result will point to the base path of the application.

      See the table below for more examples.

      When you would want to use resolveRelativeUrl:

      Using HTML5 History API or in a plain HTML session (without ugly internal paths), the internal path is present as a full part of the URL. This has a consequence that relative URLs, if not dealt with, would be resolved against the last 'folder' name of the internal path, rather than against the application deployment path (which is what you probably want).

      When using a widgetset mode deployment, or when configuring a baseURL property in the configuration, this method will make an absolute URL so that the property is fetched from the right server.

      Otherwise, this method will fixup a relative URL so that it resolves correctly against the base path of an application. This does not necessarily mean that the URL is resolved into an absolute URL. In fact, JWt will simply prepend a sequence of "../" path elements to correct for the internal path. When passed an absolute URL (i.e. starting with '/'), the url is returned unchanged.

      For URLs passed to the JWt API (and of which the library knows it represents a URL) this method is called internally by the library. But it may be useful for URLs which are set e.g. inside a WTemplate.


      Note that whether the deployment path and entry point ends with a slash is significant. Below are some examples with the deployment path in red and the internal path in blue.

      Current full path url argument Result points to
      Deployment path: /foo/bar (no slash at the end)
      Internal path: /internal/path
      (empty string)
      Deployment path: /foo/bar/ (with slash at the end)
      Internal path: /internal/path
      Note that the slash between the deployment path and the internal path is shared
      (empty string)
    • getBookmarkUrl

      public String getBookmarkUrl()
      Returns a bookmarkable URL for the current internal path.

      Is equivalent to bookmarkUrl(internalPath()), see getBookmarkUrl().

      To obtain a URL that is refers to the current session of the application, use url() instead.

      See Also:
    • getBookmarkUrl

      public String getBookmarkUrl(String internalPath)
      Returns a bookmarkable URL for a given internal path.

      Returns the (relative) URL for this application that includes the internal path internalPath, usable across sessions.

      The returned URL concatenates the internal path to the application base URL, and when no JavaScript is available and URL rewriting is used for session-tracking, a session Id is appended to reuse an existing session if available.

      You can use getBookmarkUrl() as the destination for a WAnchor, and listen to a click event is attached to a slot that switches to the internal path internalPath (see WAnchor::setRefInternalPath()). In this way, an anchor can be used to switch between internal paths within an application regardless of the situation (browser with or without Ajax support, or a web spider bot), but still generates suitable URLs across sessions, which can be used for bookmarking, opening in a new window/tab, or indexing.

      To obtain a URL that refers to the current session of the application, use url() instead.

      See Also:
    • setInternalPath

      public void setInternalPath(String path, boolean emitChange)
      Changes the internal path.

      A JWt application may manage multiple virtual paths. The virtual path is appended to the application URL. Depending on the situation, the path is directly appended to the application URL or it is appended using a name anchor (#).

      For example, for an application deployed at:

      for which an internalPath "/project/z3cbc/details/" is set, the two forms for the application URL are:
      • in an AJAX session (HTML5):
      • in an AJAX session (HTML4):
      • in a plain HTML session:

      Note, since JWt 3.1.9, the actual form of the URL no longer affects relative URL resolution, since now JWt includes an HTML meta base tag which points to the deployment path, regardless of the current internal path. This does break deployments behind a reverse proxy which changes paths.

      When the internal path is changed, an entry is added to the browser history. When the user navigates back and forward through this history (using the browser back/forward buttons), an internalPathChanged() event is emitted. You should listen to this signal to switch the application to the corresponding state. When emitChange is true, this signal is also emitted by setting the path (but only if the path is actually changed).

      A url that includes the internal path may be obtained using getBookmarkUrl().

      The internalPath must start with a '/'. In this way, you can still use normal anchors in your HTML. Internal path changes initiated in the browser to paths that do not start with a '/' are ignored.

      The emitChange parameter determines whether calling this method causes the internalPathChanged() signal to be emitted.

      See Also:
    • setInternalPath

      public final void setInternalPath(String path)
      Changes the internal path.

      Calls setInternalPath(path, false)

    • setInternalPathDefaultValid

      public void setInternalPathDefaultValid(boolean valid)
      Sets whether an internal path is valid by default.

      This configures how you treat (invalid) internal paths. If an internal path is treated valid by default then you need to call setInternalPath(false) for an invalid path. If on the other hand you treat an internal path as invalid by default, then you need to call setInternalPath(true) for a valid path.

      A user which opens an invalid internal path will receive a HTTP 404-Not Found response code (if sent an HTML response).

      The default value is true.

    • isInternalPathDefaultValid

      public boolean isInternalPathDefaultValid()
      Returns whether an internal path is valid by default.

      See Also:
    • setInternalPathValid

      public void setInternalPathValid(boolean valid)
      Sets whether the current internal path is valid.

      You can use this function in response to an internal path change event (or at application startup) to indicate whether the new (or initial) internal path is valid. This has only an effect on plain HTML sessions, or on the first response in an application deployed with progressive bootstrap settings, as this generates then a 404 Not-Found response.

      See Also:
    • isInternalPathValid

      public boolean isInternalPathValid()
      Returns whether the current internal path is valid.

      See Also:
    • getInternalPath

      public String getInternalPath()
      Returns the current internal path.

      When the application is just created, this is equal to WEnvironment.getInternalPath().

      See Also:
    • getInternalPathNextPart

      public String getInternalPathNextPart(String path)
      Returns a part of the current internal path.

      This is a convenience method which returns the next folder in the internal path, after the given path.

      For example, when the current internal path is "/project/z3cbc/details" , this method returns "details" when called with "/project/z3cbc/" as path argument.

      The path must start with a '/', and internalPathMatches() should evaluate to true for the given path. If not, an empty string is returned and an error message is logged.

      See Also:
    • internalSubPath

      public String internalSubPath(String path)
    • internalPathMatches

      public boolean internalPathMatches(String path)
      Checks if the internal path matches a given path.

      Returns whether the current getInternalPath() starts with path (or is equal to path). You will typically use this method within a slot conneted to the internalPathChanged() signal, to check that an internal path change affects the widget. It may also be useful before changing path using setInternalPath() if you do not intend to remove sub paths when the current internal path already matches path.

      The path must start with a '/'.

      See Also:
    • internalPathChanged

      public Signal1<String> internalPathChanged()
      Signal which indicates that the user changes the internal path.

      This signal indicates a change to the internal path, which is usually triggered by the user using the browser back/forward buttons.

      The argument contains the new internal path.

      See Also:
    • internalPathInvalid

      public Signal1<String> internalPathInvalid()
      Signal which indicates that an invalid internal path is navigated.
    • redirect

      public void redirect(String url)
      Redirects the application to another location.

      The client will be redirected to a new location identified by url. Use this in conjunction with quit() if you want the application to be terminated as well.

      Calling redirect() does not imply quit() since it may be useful to switch between a non-secure and secure (SSL) transport connection.

    • getResourcesUrl

      public static String getResourcesUrl()
      Returns the URL at which the resources are deployed.

      Returns resolveRelativeUrl(relativeResourcesUrl())

    • getRelativeResourcesUrl

      public static String getRelativeResourcesUrl()
      Returns the URL at which the resources are deployed.

      See Also:
    • getSessionId

      public String getSessionId()
      Returns the unique identifier for the current session.

      The session id is a string that uniquely identifies the current session. Note that the actual contents has no particular meaning and client applications should in no way try to interpret its value.

    • enableUpdates

      public void enableUpdates(boolean enabled)
      Enables server-initiated updates.

      By default, updates to the user interface are possible only at startup, during any event (in a slot), or at regular time points using WTimer. This is the normal JWt event loop.

      In some cases, one may want to modify the user interface from a second thread, outside the event loop. While this may be worked around by the WTimer, in some cases, there are bandwidth and processing overheads associated which may be unnecessary, and which create a trade-off with time resolution of the updates.

      When enabled is true, this enables "server push" (what is called 'comet' in AJAX terminology). Widgets may then be modified, created or deleted outside of the event loop (e.g. in response to execution of another thread), and these changes are propagated by calling triggerUpdate().

      Note that you need to grab the application's update lock to avoid concurrency problems, whenever you modify the application's state from another thread.

      An example of how to modify the widget tree outside the event loop and propagate changes is:

       // You need to have a reference to the application whose state
       // you are about to manipulate.
       WApplication app = ...;
       // Grab the application lock
       WApplication.UpdateLock lock = app.getUpdateLock();
       try {
       // We now have exclusive access to the application:
       // we can safely modify the widget tree for example.
       app.getRoot().addWidget(new WText("Something happened!"));
       // Push the changes to the browser
       } finally {

      This works only if your servlet container supports the Servlet 3.0 API. If you try to invoke this function on a servlet container with no such support, an exception will be thrown.

      Note: This works only if JavaScript is available on the client.

      See Also:
    • enableUpdates

      public final void enableUpdates()
      Enables server-initiated updates.

      Calls enableUpdates(true)

    • isUpdatesEnabled

      public boolean isUpdatesEnabled()
      Returns whether server-initiated updates are enabled.

      See Also:
    • triggerUpdate

      public void triggerUpdate()
      Propagates server-initiated updates.

      When the lock to the application is released, changes will propagate to the user interface. This call only has an effect after updates have been enabled from within the normal event loop using enableUpdates().

      This is typically used only outside of the main event loop, e.g. from another thread or from within a method posted to an application using WServer::post(), since changes always propagate within the event loop at the end of the event.

      The update is not immediate, and thus changes that happen after this call will equally be pushed to the client.

      See Also:
    • getUpdateLock

      public WApplication.UpdateLock getUpdateLock()
      Grabs and returns the lock for manipulating widgets outside the event loop.

      You need to keep this lock in scope while manipulating widgets outside of the event loop. In normal cases, inside the JWt event loop, you do not need to care about it.

      See Also:
    • attachThread

      public void attachThread(boolean attach)
      Attach an auxiliary thread to this application.

      In a multi-threaded environment, getInstance() uses thread-local data to retrieve the application object that corresponds to the session currently being handled by the thread. This is set automatically by the library whenever an event is delivered to the application, or when you use the WApplication.UpdateLock to modify the application from an auxiliary thread outside the normal event loop.

      When you want to manipulate the widget tree inside the main event loop, but from within an auxiliary thread, then you cannot use the WApplication.UpdateLock since this will create an immediate dead lock. Instead, you may attach the auxiliary thread to the application, by calling this method from the auxiliary thread, and in this way you can modify the application from within that thread without needing the update lock.

      Calling attachThread() with attach = false, detaches the current thread.

    • attachThread

      public final void attachThread()
      Attach an auxiliary thread to this application.

      Calls attachThread(true)

    • doJavaScript

      public void doJavaScript(String javascript, boolean afterLoaded)
      Executes some JavaScript code.

      This method may be used to call some custom javaScript code as part of an event response.

      This function does not wait until the JavaScript is run, but returns immediately. The JavaScript will be run after the normal event handling, unless afterLoaded is set to false.

      In most situations, it's more robust to use WWidget#doJavaScript() however.

      See Also:
    • doJavaScript

      public final void doJavaScript(String javascript)
      Executes some JavaScript code.

      Calls doJavaScript(javascript, true)

    • addAutoJavaScript

      public void addAutoJavaScript(String javascript)
      Adds JavaScript statements that should be run continuously.

      This is an internal method.

      It is used by for example layout managers to adjust the layout whenever the DOM tree is manipulated.

      See Also:
    • declareJavaScriptFunction

      public void declareJavaScriptFunction(String name, String function)
      Declares an application-wide JavaScript function.

      The function is stored in getJavaScriptClass().

      The next code snippet declares and invokes function foo:

    • require

      public boolean require(String uri, String symbol)
      Loads a JavaScript library.

      Loads a JavaScript library located at the URL url. JWt keeps track of libraries (with the same URL) that already have been loaded, and will load a library only once. In addition, you may provide a symbol which if already defined will also indicate that the library was already loaded (possibly outside of JWt when in EntryPointType.WidgetSet mode).

      This method returns true only when the library is loaded for the first time.

      JavaScript libraries may be loaded at any point in time. Any JavaScript code is deferred until the library is loaded, except for JavaScript that was defined to load before, passing false as second parameter to doJavaScript().

    • require

      public final boolean require(String uri)
      Loads a JavaScript library.

      Returns require(uri, "")

    • requireJQuery

      public boolean requireJQuery(String uri)
    • isCustomJQuery

      public boolean isCustomJQuery()
    • setJavaScriptClass

      public void setJavaScriptClass(String javaScriptClass)
      Sets the name of the application JavaScript class.

      This should be called right after construction of the application, and changing the JavaScript class is only supported for EntryPointType.WidgetSet mode applications. The className should be a valid JavaScript identifier, and should also be unique in a single page.

    • getJavaScriptClass

      public String getJavaScriptClass()
      Returns the name of the application JavaScript class.

      This JavaScript class encapsulates all JavaScript methods specific to this application instance. The method is foreseen to allow multiple applications to run simultaneously on the same page in Wt::WidgtSet mode, without interfering.

    • processEvents

      public void processEvents()
      Processes UI events.

      You may call this method during a long operation to:

      • propagate widget changes to the client.
      • process UI events.

      This method starts a recursive event loop, blocking the current thread, and resumes when all pending user interface events have been processed.

      Because a thread is blocked, this may affect your application scalability.

    • waitForEvent

      public void waitForEvent()
      Blocks the thread, waiting for an UI event.

      This function is used by functions like WDialog#exec() or WPopupMenu::exec(), to block the current thread waiting for a new event.

      This requires that at least one additional thread is available to process incoming requests, and is not scalable when working with a fixed size thread pools.

    • readConfigurationProperty

      public static String readConfigurationProperty(String name, String value)
      Reads a configuration property.

      Tries to read a configured value for the property name. If no value was configured, the default value is returned.

    • getDomRoot

      public WWebWidget getDomRoot()
    • destroy

      public void destroy()
      Destroys the application session.

      The application is destroyed when the session is invalidated. You should put here any logic which is needed to cleanup the application session.

      The default implementation does nothing.

    • setTwoPhaseRenderingThreshold

      public void setTwoPhaseRenderingThreshold(int bytes)
      Changes the threshold for two-phase rendering.

      This changes the threshold for the size of a JavaScript response (in bytes) to render invisible changes in one go. If the bandwidth for rendering the invisible changes exceed the threshold, they will be fetched in a second communication, after the visible changes have been rendered.

      The value is a trade-off: setting it smaller will always use two-phase rendering, increasing the total render time but reducing the latency for the visible changes. Setting it too large will increase the latency to render the visible changes, since first also all invisible changes need to be computed and received in the browser.

    • setCookie

      public void setCookie(javax.servlet.http.Cookie cookie)
      Sets a new cookie.

      Use cookies to transfer information across different sessions (e.g. a user name). In a subsequent session you will be able to read this cookie using WEnvironment#getCookie(). You cannot use a cookie to store information in the current session.

      For more information on how to configure cookies, see the Http::Cookie class.

      See Also:
    • setCookie

      public void setCookie(String name, String value, int maxAge, String domain, String path, boolean secure)
      Use setCookie() instead.
      Sets a new cookie.

      Use cookies to transfer information across different sessions (e.g. a user name). In a subsequent session you will be able to read this cookie using WEnvironment#getCookie(). You cannot use a cookie to store information in the current session.

      The name must be a valid cookie name (of type 'token': no special characters or separators, see RFC2616 page 16). The value may be anything. Specify the maximum age (in seconds) after which the client must discard the cookie. To delete a cookie, use a value of '0'.

      By default the cookie only applies to the application deployment path (WEnvironment.getDeploymentPath()) in the current domain. To set a proper value for domain, see also RFC2109.

      See Also:
    • setCookie

      public final void setCookie(String name, String value, int maxAge)
    • setCookie

      public final void setCookie(String name, String value, int maxAge, String domain)
    • setCookie

      public final void setCookie(String name, String value, int maxAge, String domain, String path)
    • removeCookie

      public void removeCookie(javax.servlet.http.Cookie cookie)
      Removes a cookie.

      The cookie will be removed if it has the same name, domain and path as the original cookie (RFC-6265, section 5.3.11).

      See Also:
    • removeCookie

      public void removeCookie(String name, String domain, String path)
      Use removeCookie() instead.
      Removes a cookie.

      See Also:
    • removeCookie

      public final void removeCookie(String name)
      Removes a cookie.

      Calls removeCookie(name, "", "")

    • removeCookie

      public final void removeCookie(String name, String domain)
      Removes a cookie.

      Calls removeCookie(name, domain, "")

    • addMetaLink

      public void addMetaLink(String href, String rel, String media, String hreflang, String type, String sizes, boolean disabled)
      Adds an HTML meta link.

      When a link was previously set for the same href, its contents are replaced. When an empty string is used for the arguments media, hreflang, type or sizes, they will be ignored.

      See Also:
    • removeMetaLink

      public void removeMetaLink(String href)
      Removes the HTML meta link.

      See Also:
    • addMetaHeader

      public void addMetaHeader(String name, CharSequence content, String lang)
      Adds a "name" HTML meta header.

      See Also:
    • addMetaHeader

      public final void addMetaHeader(String name, CharSequence content)
      Adds a "name" HTML meta header.

      Calls addMetaHeader(name, content, "")

    • addMetaHeader

      public void addMetaHeader(MetaHeaderType type, String name, CharSequence content, String lang)
      Adds an HTML meta header.

      This method sets either a "name" meta headers, which configures a document property, or a "http-equiv" meta headers, which defines a HTTP headers (but these latter headers are being deprecated).

      A meta header can however only be added in the following situations:

      • when a plain HTML session is used (including when the user agent is a bot), you can add meta headers at any time.
      • or, when progressive bootstrap is used, you can set meta headers for any type of session, from within the application constructor (which corresponds to the initial request).
      • but never for a EntryPointType.WidgetSet mode application since then the application is hosted within a foreign HTML page.

      These situations coincide with WEnvironment.hasAjax() returning false (see getEnvironment()). The reason that it other cases the HTML page has already been rendered, and will not be rerendered since all updates are done dynamically.

      As an alternative, you can use the <meta-headers> configuration property in the configuration file, which will be applied in all circumstances.

      See Also:
    • addMetaHeader

      public final void addMetaHeader(MetaHeaderType type, String name, CharSequence content)
      Adds an HTML meta header.

      Calls addMetaHeader(type, name, content, "")

    • metaHeader

      public WString metaHeader(MetaHeaderType type, String name)
      Returns a meta header value.

      See Also:
    • removeMetaHeader

      public void removeMetaHeader(MetaHeaderType type, String name)
      Removes one or all meta headers.

      Removes the meta header with given type and name (if it is present). If name is empty, all meta headers of the given type are removed.

      See Also:
    • removeMetaHeader

      public final void removeMetaHeader(MetaHeaderType type)
      Removes one or all meta headers.

      Calls removeMetaHeader(type, "")

    • setLoadingIndicator

      public void setLoadingIndicator(WLoadingIndicator indicator)
      Sets the loading indicator.

      The loading indicator is shown to indicate that a response from the server is pending or JavaScript is being evaluated.

      The default loading indicator is a WDefaultLoadingIndicator.

    • getLoadingIndicator

      public WLoadingIndicator getLoadingIndicator()
      Returns the loading indicator.

      See Also:
    • quit

      public void quit()
      Quits the application.

      This quits the application with a default restart message resolved as WString#tr()("Wt.QuittedMessage").

      See Also:
    • quit

      public void quit(CharSequence restartMessage)
      Quits the application.

      The method returns immediately, but has as effect that the application will be terminated after the current event is completed.

      The current widget tree (including any modifications still pending and applied during the current event handling) will still be rendered, after which the application is terminated.

      If the restart message is not empty, then the user will be offered to restart the application (using the provided message) when further interacting with the application.

      See Also:
    • hasQuit

      public boolean hasQuit()
      Returns whether the application has quit.

      See Also:
    • getMaximumRequestSize

      public long getMaximumRequestSize()
      Returns the current maximum size of a request to the application.

      The returned value is the maximum request size in bytes.

      See Also:
    • requestTooLarge

      public Signal1<Long> requestTooLarge()
      Signal which indicates that too a large request was received.

      The integer parameter is the request size that was received in bytes.

    • globalKeyWentDown

      public EventSignal1<WKeyEvent> globalKeyWentDown()
      Event signal emitted when a keyboard key is pushed down.

      The application receives key events when no widget currently has focus. Otherwise, key events are handled by the widget in focus, and its ancestors.

      See Also:
    • globalKeyPressed

      public EventSignal1<WKeyEvent> globalKeyPressed()
      Event signal emitted when a "character" was entered.

      The application receives key events when no widget currently has focus. Otherwise, key events are handled by the widget in focus, and its ancestors.

      See Also:
    • globalKeyWentUp

      public EventSignal1<WKeyEvent> globalKeyWentUp()
      Event signal emitted when a keyboard key is released.

      The application receives key events when no widget currently has focus. Otherwise, key events are handled by the widget in focus, and its ancestors.

      See Also:
    • globalEnterPressed

      public EventSignal globalEnterPressed()
      Event signal emitted when enter was pressed.

      The application receives key events when no widget currently has focus. Otherwise, key events are handled by the widget in focus, and its ancestors.

      See Also:
    • globalEscapePressed

      public EventSignal globalEscapePressed()
      Event signal emitted when escape was pressed.

      The application receives key events when no widget currently has focus. Otherwise, key events are handled by the widget in focus, and its ancestors.

      See Also:
    • setFocus

      public void setFocus(String id, int selectionStart, int selectionEnd)
    • loadJavaScript

      public void loadJavaScript(String jsFile, WJavaScriptPreamble preamble)
      Loads an internal JavaScript file.

      This is an internal function and should not be called directly.

      See Also:
    • setConfirmCloseMessage

      public void setConfirmCloseMessage(CharSequence message)
      Sets the message for the user to confirm closing of the application window/tab.

      If the message is empty, then the user may navigate away from the page without confirmation.

      Otherwise the user will be prompted with a browser-specific dialog asking him to confirm leaving the page. This message is added to the page.

      See Also:
    • pathMatches

      public static boolean pathMatches(String path, String query)
      Utility function to check if one path falls under another path.

      This returns whether the query path matches the given path, meaning that it is equal to that path or it specifies a more specific sub path of that path.

    • encodeUntrustedUrl

      public String encodeUntrustedUrl(String url)
      Encodes an untrusted URL to prevent referer leaks.

      This encodes an URL so that in case the session ID is present in the current URL, this session ID does not leak to the refenced URL.

      Wt will safely handle URLs in the API (in WImage and WAnchor) but you may want to use this function to encode URLs which you use in WTemplate texts.

    • addGlobalWidget

      public void addGlobalWidget(WWidget w)
    • removeGlobalWidget

      public void removeGlobalWidget(WWidget w)
    • suspend

      public void suspend(Duration duration)
      Suspend the application.

      Keep this application alive for a certain amount of time, while allowing the user to navigate away from the page. This can be useful when using 3rd party login or payment providers. You can later return to the application with a url that includes the session ID as query parameter (see url()).

    • unsuspended

      public Signal unsuspended()
      Signal that is emitted when the application is no longer suspended.

      This can be used to apply changes which were difficult to do as a result of the application not being rendered. Eg. JWt uses this to trigger a login as a result of single sign-on.

    • notify

      protected void notify(WEvent e) throws IOException
      Notifies an event to the application.

      This method is called by the event loop for propagating an event to the application. It provides a single point of entry for events to the application, besides the application constructor.

      You may want to reimplement this method for two reasons:

      • for having a single point for exception handling: while you may want to catch recoverable exceptions in a more appropriate place, general (usually fatal) exceptions may be caught here. You will probably want to catch the same exceptions in the application constructor in the same way.
      • you want to manage resource usage during requests. For example, at the end of request handling, you want to return a database session back to the pool. Since notify() is also used for rendering right after the application is created, this will also clean up resources after application construction.

      In either case, you will need to call the base class implementation of notify(), as otherwise no events will be delivered to your application.

      The following shows a generic template for reimplementhing this method for both managing request resources and generic exception handling.

       void notify(WEvent event) {
       // Grab resources for during request handling
       try {
       }  catch (MyException exception) {
       // handle this exception in a central place
       // Free resources used during request handling

      Note that any uncaught exception throw during event handling terminates the session.

    • isExposed

      protected boolean isExposed(WWidget w)
      Returns whether a widget is exposed in the interface.

      The default implementation simply returns true, unless a modal dialog is active, in which case it returns true only for widgets that are inside the dialog.

      You may want to reimplement this method if you wish to disallow events from certain widgets even when they are inserted in the widget hierachy.

    • enableAjax

      protected void enableAjax()
      Progresses to an Ajax-enabled user interface.

      This method is called when the progressive bootstrap method is used, and support for AJAX has been detected. The default behavior will propagate the WWidget.enableAjax() method through the widget hierarchy.

      You may want to reimplement this method if you want to make changes to the user-interface when AJAX is enabled. You should always call the base implementation.

      See Also:
    • unload

      protected void unload()
      Handles a browser unload event.

      The browser unloads the application when the user navigates away or when he closes the window or tab.

      When reload-is-new-session is set to true, then the default implementation of this method terminates this session by calling quit(), otherwise the session is scheduled to expire within seconds (since it may be a refresh).

      You may want to reimplement this if you want to keep the application running until it times out.

      Note: There is no guarantee that closing the browser tab sends the unload event. This is because it is at the web browser's discretion whether it still sends requests for a closed tab. It's also possible that there was no connection upon closing the tab. Sessions that don't receive the unload event will eventually time out according to the session-timeout set in wt_config.xml (this defaults to 10 minutes).

    • idleTimeout

      protected void idleTimeout()
      Idle timeout handler.

      If idle timeout is set in the configuration (Configuration#setIdleTimeout(int)), this method is called when the user seems idle for the number of seconds set as the idle timeout.

      This feature can be useful in security sensitive applications to prevent unauthorized users from taking over the session of a user that has moved away from or left behind the device from which they are accessing the JWt application.

      The default implementation logs that a timeout has occurred, and calls quit().

      This method can be overridden to specify different timeout behaviour, e.g. to show a dialog that a user's session has expired, or that the session is about to expire.

      Note: The events currently counted as user activity are:

      • mousedown
      • mouseup
      • wheel
      • keydown
      • keyup
      • touchstart
      • touchend
      • pointerdown
      • pointerup
    • handleJavaScriptError

      protected void handleJavaScriptError(String errorText)
      handleJavaScriptError print javaScript errors to log file. You may want to overwrite it to render error page for example.

      errorText - the error will usually be in json format.