Module javafx.web
Package javafx.scene.web

## Class WebEngine

- java.lang.Object
- - javafx.scene.web.WebEngine

-     public final class WebEngine
      extends Object

  `WebEngine` is a non-visual object capable of managing one Web page at a time. It loads Web pages, creates their document models, applies styles as necessary, and runs JavaScript on pages. It provides access to the document model of the current page, and enables two-way communication between a Java application and JavaScript code of the page.

  Loading Web Pages

  The `WebEngine` class provides two ways to load content into a `WebEngine` object:

  - From an arbitrary URL using the `load(java.lang.String)` method. This method uses the `java.net` package for network access and protocol handling.
  - From an in-memory String using the `loadContent(java.lang.String, java.lang.String)` and `loadContent(java.lang.String)` methods.

  Loading always happens on a background thread. Methods that initiate loading return immediately after scheduling a background job. To track progress and/or cancel a job, use the `Worker` instance available from the `getLoadWorker()` method.

  The following example changes the stage title when loading completes successfully:

          import javafx.concurrent.Worker.State;
          final Stage stage;
          webEngine.getLoadWorker().stateProperty().addListener(
              new ChangeListener<State>() {
                  public void changed(ObservableValue ov, State oldState, State newState) {
                      if (newState == State.SUCCEEDED) {
                          stage.setTitle(webEngine.getLocation());
                      }
                  }
              });
          webEngine.load("http://javafx.com");

  User Interface Callbacks

  A number of user interface callbacks may be registered with a `WebEngine` object. These callbacks are invoked when a script running on the page requests a user interface operation to be performed, for example, opens a popup window or changes status text. A `WebEngine` object cannot handle such requests internally, so it passes the request to the corresponding callbacks. If no callback is defined for a specific operation, the request is silently ignored.

  The table below shows JavaScript user interface methods and properties with their corresponding `WebEngine` callbacks:

  JavaScript Callback Table
  JavaScript method/property | WebEngine callback
  --- | ---
  `window.alert()` | `onAlert`
  `window.confirm()` | `confirmHandler`
  `window.open()` | `createPopupHandler`
  `window.open()` and `window.close()` | `onVisibilityChanged`
  `window.prompt()` | `promptHandler`
  Setting `window.status` | `onStatusChanged`
  Setting any of the following: `window.innerWidth`, `window.innerHeight`, `window.outerWidth`, `window.outerHeight`, `window.screenX`, `window.screenY`, `window.screenLeft`, `window.screenTop` | `onResized`

  The following example shows a callback that resizes a browser window:

          Stage stage;
          webEngine.setOnResized(
              new EventHandler<WebEvent<Rectangle2D>>() {
                  public void handle(WebEvent<Rectangle2D> ev) {
                      Rectangle2D r = ev.getData();
                      stage.setWidth(r.getWidth());
                      stage.setHeight(r.getHeight());
                  }
              });

  Access to Document Model

  The `WebEngine` objects create and manage a Document Object Model (DOM) for their Web pages. The model can be accessed and modified using Java DOM Core classes. The `getDocument()` method provides access to the root of the model. Additionally DOM Event specification is supported to define event handlers in Java code.

  The following example attaches a Java event listener to an element of a Web page. Clicking on the element causes the application to exit:

          EventListener listener = new EventListener() {
              public void handleEvent(Event ev) {
                  Platform.exit();
              }
          };

          Document doc = webEngine.getDocument();
          Element el = doc.getElementById("exit-app");
          ((EventTarget) el).addEventListener("click", listener, false);

  Evaluating JavaScript expressions

  It is possible to execute arbitrary JavaScript code in the context of the current page using the `executeScript(java.lang.String)` method. For example:

          webEngine.executeScript("history.back()");

  The execution result is returned to the caller, as described in the next section.

  Mapping JavaScript values to Java objects

  JavaScript values are represented using the obvious Java classes: null becomes Java null; a boolean becomes a `java.lang.Boolean`; and a string becomes a `java.lang.String`. A number can be `java.lang.Double` or a `java.lang.Integer`, depending. The undefined value maps to a specific unique String object whose value is `"undefined"`.

  If the result is a JavaScript object, it is wrapped as an instance of the `JSObject` class. (As a special case, if the JavaScript object is a `JavaRuntimeObject` as discussed in the next section, then the original Java object is extracted instead.) The `JSObject` class is a proxy that provides access to methods and properties of its underlying JavaScript object. The most commonly used `JSObject` methods are `getMember` (to read a named property), `setMember` (to set or define a property), and `call` (to call a function-valued property).

  A DOM `Node` is mapped to an object that both extends `JSObject` and implements the appropriate DOM interfaces. To get a `JSObject` object for a `Node` just do a cast:

       JSObject jdoc = (JSObject) webEngine.getDocument();

  In some cases the context provides a specific Java type that guides the conversion. For example if setting a Java `String` field from a JavaScript expression, then the JavaScript value is converted to a string.

  Mapping Java objects to JavaScript values

  The arguments of the `JSObject` methods `setMember` and `call` pass Java objects to the JavaScript environment. This is roughly the inverse of the JavaScript-to-Java mapping described above: Java `String`, `Number`, or `Boolean` objects are converted to the obvious JavaScript values. A `JSObject` object is converted to the original wrapped JavaScript object. Otherwise a `JavaRuntimeObject` is created. This is a JavaScript object that acts as a proxy for the Java object, in that accessing properties of the `JavaRuntimeObject` causes the Java field or method with the same name to be accessed.

  Note that the Java objects bound using `JSObject.setMember`, `JSObject.setSlot`, and `JSObject.call` are implemented using weak references. This means that the Java object can be garbage collected, causing subsequent accesses to the JavaScript objects to have no effect.

  Calling back to Java from JavaScript

  The `JSObject.setMember` method is useful to enable upcalls from JavaScript into Java code, as illustrated by the following example. The Java code establishes a new JavaScript object named `app`. This object has one public member, the method `exit`.

      public class JavaApplication {
          public void exit() {
              Platform.exit();
          }
      }
      ...
      JavaApplication javaApp = new JavaApplication();
      JSObject window = (JSObject) webEngine.executeScript("window");
      window.setMember("app", javaApp);

  You can then refer to the object and the method from your HTML page:

          <a href="" onclick="app.exit()">Click here to exit application</a>

  When a user clicks the link the application is closed.

  Note that in the above example, the application holds a reference to the `JavaApplication` instance. This is required for the callback from JavaScript to execute the desired method.

  In the following example, the application does not hold a reference to the Java object:

       JSObject window = (JSObject) webEngine.executeScript("window");
       window.setMember("app", new JavaApplication());

  In this case, since the property value is a local object, `"new JavaApplication()"`, the value may be garbage collected in next GC cycle.

  When a user clicks the link, it does not guarantee to execute the callback method `exit`.

  If there are multiple Java methods with the given name, then the engine selects one matching the number of parameters in the call. (Varargs are not handled.) An unspecified one is chosen if there are multiple ones with the correct number of parameters.

  You can pick a specific overloaded method by listing the parameter types in an "extended method name", which has the form `"method_name(param_type1,...,param_typen)"`. Typically you'd write the JavaScript expression:

       receiver["method_name(param_type1,...,param_typeN)"](arg1,...,argN)

  The Java class and method must both be declared public.

  Deploying an Application as a Module

  If any Java class passed to JavaScript is in a named module, then it must be reflectively accessible to the `javafx.web` module. A class is reflectively accessible if the module `opens` the containing package to at least the `javafx.web` module. Otherwise, the method will not be called, and no error or warning will be produced.

  For example, if `com.foo.MyClass` is in the `foo.app` module, the `module-info.java` might look like this:

      module foo.app {
          opens com.foo to javafx.web;
      }

  Alternatively, a class is reflectively accessible if the module `exports` the containing package unconditionally.

  Threading

  `WebEngine` objects must be created and accessed solely from the JavaFX Application thread. This rule also applies to any DOM and JavaScript objects obtained from the `WebEngine` object.

  Since:
    JavaFX 2.0

- - ### Property Summary

    Properties
    Type | Property | Description
    --- | --- | ---
    `ObjectProperty<Callback<String,​Boolean>>` | `confirmHandler` | JavaScript `confirm` handler property.
    `ObjectProperty<Callback<PopupFeatures,​WebEngine>>` | `createPopupHandler` | JavaScript popup handler property.
    `ReadOnlyObjectProperty<Document>` | `document` | Document object for the current Web page.
    `BooleanProperty` | `javaScriptEnabled` | Specifies whether JavaScript execution is enabled.
    `ReadOnlyStringProperty` | `location` | URL of the current Web page.
    `ObjectProperty<EventHandler<WebEvent<String>>>` | `onAlert` | JavaScript `alert` handler property.
    `ObjectProperty<EventHandler<WebErrorEvent>>` | `onError` | The event handler called when an error occurs.
    `ObjectProperty<EventHandler<WebEvent<Rectangle2D>>>` | `onResized` | JavaScript window resize handler property.
    `ObjectProperty<EventHandler<WebEvent<String>>>` | `onStatusChanged` | JavaScript status handler property.
    `ObjectProperty<EventHandler<WebEvent<Boolean>>>` | `onVisibilityChanged` | JavaScript window visibility handler property.
    `ObjectProperty<Callback<PromptData,​String>>` | `promptHandler` | JavaScript `prompt` handler property.
    `ReadOnlyStringProperty` | `title` | Title of the current Web page.
    `StringProperty` | `userAgent` | Specifies user agent ID string.
    `ObjectProperty<File>` | `userDataDirectory` | Specifies the directory to be used by this `WebEngine` to store local user data.
    `StringProperty` | `userStyleSheetLocation` | Location of the user stylesheet as a string URL.

  - ### Constructor Summary

    Constructors
    Constructor | Description
    --- | ---
    `WebEngine()` | Creates a new engine.
    `WebEngine​(String url)` | Creates a new engine and loads a Web page into it.

  - ### Method Summary

    Modifier and Type | Method | Description
    --- | --- | ---
    `ObjectProperty<Callback<String,​Boolean>>` | `confirmHandlerProperty()` | JavaScript `confirm` handler property.
    `ObjectProperty<Callback<PopupFeatures,​WebEngine>>` | `createPopupHandlerProperty()` | JavaScript popup handler property.
    `ReadOnlyObjectProperty<Document>` | `documentProperty()` | Document object for the current Web page.
    `Object` | `executeScript​(String script)` | Executes a script in the context of the current page.
    `Callback<String,​Boolean>` | `getConfirmHandler()` | Gets the value of the property confirmHandler.
    `Callback<PopupFeatures,​WebEngine>` | `getCreatePopupHandler()` | Gets the value of the property createPopupHandler.
    `Document` | `getDocument()` | Gets the value of the property document.
    `WebHistory` | `getHistory()` | Returns the session history object.
    `Worker<Void>` | `getLoadWorker()` | Returns a `Worker` object that can be used to track loading progress.
    `String` | `getLocation()` | Gets the value of the property location.
    `EventHandler<WebEvent<String>>` | `getOnAlert()` | Gets the value of the property onAlert.
    `EventHandler<WebErrorEvent>` | `getOnError()` | Gets the value of the property onError.
    `EventHandler<WebEvent<Rectangle2D>>` | `getOnResized()` | Gets the value of the property onResized.
    `EventHandler<WebEvent<String>>` | `getOnStatusChanged()` | Gets the value of the property onStatusChanged.
    `EventHandler<WebEvent<Boolean>>` | `getOnVisibilityChanged()` | Gets the value of the property onVisibilityChanged.
    `Callback<PromptData,​String>` | `getPromptHandler()` | Gets the value of the property promptHandler.
    `String` | `getTitle()` | Gets the value of the property title.
    `String` | `getUserAgent()` | Gets the value of the property userAgent.
    `File` | `getUserDataDirectory()` | Gets the value of the property userDataDirectory.
    `String` | `getUserStyleSheetLocation()` | Gets the value of the property userStyleSheetLocation.
    `boolean` | `isJavaScriptEnabled()` | Gets the value of the property javaScriptEnabled.
    `BooleanProperty` | `javaScriptEnabledProperty()` | Specifies whether JavaScript execution is enabled.
    `void` | `load​(String url)` | Loads a Web page into this engine.
    `void` | `loadContent​(String content)` | Loads the given HTML content directly.
    `void` | `loadContent​(String content, String contentType)` | Loads the given content directly.
    `ReadOnlyStringProperty` | `locationProperty()` | URL of the current Web page.
    `ObjectProperty<EventHandler<WebEvent<String>>>` | `onAlertProperty()` | JavaScript `alert` handler property.
    `ObjectProperty<EventHandler<WebErrorEvent>>` | `onErrorProperty()` | The event handler called when an error occurs.
    `ObjectProperty<EventHandler<WebEvent<Rectangle2D>>>` | `onResizedProperty()` | JavaScript window resize handler property.
    `ObjectProperty<EventHandler<WebEvent<String>>>` | `onStatusChangedProperty()` | JavaScript status handler property.
    `ObjectProperty<EventHandler<WebEvent<Boolean>>>` | `onVisibilityChangedProperty()` | JavaScript window visibility handler property.
    `void` | `print​(PrinterJob job)` | Prints the current Web page using the given printer job.
    `ObjectProperty<Callback<PromptData,​String>>` | `promptHandlerProperty()` | JavaScript `prompt` handler property.
    `void` | `reload()` | Reloads the current page, whether loaded from URL or directly from a String in one of the `loadContent` methods.
    `void` | `setConfirmHandler​(Callback<String,​Boolean> handler)` | Sets the value of the property confirmHandler.
    `void` | `setCreatePopupHandler​(Callback<PopupFeatures,​WebEngine> handler)` | Sets the value of the property createPopupHandler.
    `void` | `setJavaScriptEnabled​(boolean value)` | Sets the value of the property javaScriptEnabled.
    `void` | `setOnAlert​(EventHandler<WebEvent<String>> handler)` | Sets the value of the property onAlert.
    `void` | `setOnError​(EventHandler<WebErrorEvent> handler)` | Sets the value of the property onError.
    `void` | `setOnResized​(EventHandler<WebEvent<Rectangle2D>> handler)` | Sets the value of the property onResized.
    `void` | `setOnStatusChanged​(EventHandler<WebEvent<String>> handler)` | Sets the value of the property onStatusChanged.
    `void` | `setOnVisibilityChanged​(EventHandler<WebEvent<Boolean>> handler)` | Sets the value of the property onVisibilityChanged.
    `void` | `setPromptHandler​(Callback<PromptData,​String> handler)` | Sets the value of the property promptHandler.
    `void` | `setUserAgent​(String value)` | Sets the value of the property userAgent.
    `void` | `setUserDataDirectory​(File value)` | Sets the value of the property userDataDirectory.
    `void` | `setUserStyleSheetLocation​(String value)` | Sets the value of the property userStyleSheetLocation.
    `ReadOnlyStringProperty` | `titleProperty()` | Title of the current Web page.
    `StringProperty` | `userAgentProperty()` | Specifies user agent ID string.
    `ObjectProperty<File>` | `userDataDirectoryProperty()` | Specifies the directory to be used by this `WebEngine` to store local user data.
    `StringProperty` | `userStyleSheetLocationProperty()` | Location of the user stylesheet as a string URL.

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Property Detail

    - #### document

          public final ReadOnlyObjectProperty<Document> documentProperty

      Document object for the current Web page. The value is `null` if the Web page failed to load.
      See Also:
        `getDocument()`

    - #### location

          public final ReadOnlyStringProperty locationProperty

      URL of the current Web page. If the current page has no URL, the value is an empty String.
      See Also:
        `getLocation()`

    - #### title

          public final ReadOnlyStringProperty titleProperty

      Title of the current Web page. If the current page has no title, the value is `null`.
      See Also:
        `getTitle()`

    - #### javaScriptEnabled

          public final BooleanProperty javaScriptEnabledProperty

      Specifies whether JavaScript execution is enabled.
      Default value:
        true
      Since:
        JavaFX 2.2
      See Also:
        `isJavaScriptEnabled()`, `setJavaScriptEnabled(boolean)`

    - #### userStyleSheetLocation

          public final StringProperty userStyleSheetLocationProperty

      Location of the user stylesheet as a string URL.

      This should be a local URL, i.e. either `'data:'`, `'file:'`, or `'jar:'`. Remote URLs are not allowed for security reasons.

      Default value:
        null
      Since:
        JavaFX 2.2
      See Also:
        `getUserStyleSheetLocation()`, `setUserStyleSheetLocation(String)`

    - #### userDataDirectory

          public final ObjectProperty<File> userDataDirectoryProperty

      Specifies the directory to be used by this `WebEngine` to store local user data.

      If the value of this property is not `null`, the `WebEngine` will attempt to store local user data in the respective directory. If the value of this property is `null`, the `WebEngine` will attempt to store local user data in an automatically selected system-dependent user- and application-specific directory.

      When a `WebEngine` is about to start loading a web page or executing a script for the first time, it checks whether it can actually use the directory specified by this property. If the check fails for some reason, the `WebEngine` invokes the `WebEngine.onError` event handler, if any, with a `WebErrorEvent` describing the reason. If the invoked event handler modifies the `userDataDirectory` property, the `WebEngine` retries with the new value as soon as the handler returns. If the handler does not modify the `userDataDirectory` property (which is the default), the `WebEngine` continues without local user data.

      Once the `WebEngine` has started loading a web page or executing a script, changes made to this property have no effect on where the `WebEngine` stores or will store local user data.

      Currently, the directory specified by this property is used only to store the data that backs the `window.localStorage` objects. In the future, more types of data can be added.

      Default value:
        `null`
      Since:
        JavaFX 8.0
      See Also:
        `getUserDataDirectory()`, `setUserDataDirectory(File)`

    - #### userAgent

          public final StringProperty userAgentProperty

      Specifies user agent ID string. This string is the value of the `User-Agent` HTTP header.
      Default value:
        system dependent
      Since:
        JavaFX 8.0
      See Also:
        `getUserAgent()`, `setUserAgent(String)`

    - #### onAlert

          public final ObjectProperty<EventHandler<WebEvent<String>>> onAlertProperty

      JavaScript `alert` handler property. This handler is invoked when a script running on the Web page calls the `alert` function.
      See Also:
        `getOnAlert()`, `setOnAlert(EventHandler)`

    - #### onStatusChanged

          public final ObjectProperty<EventHandler<WebEvent<String>>> onStatusChangedProperty

      JavaScript status handler property. This handler is invoked when a script running on the Web page sets `window.status` property.
      See Also:
        `getOnStatusChanged()`, `setOnStatusChanged(EventHandler)`

    - #### onResized

          public final ObjectProperty<EventHandler<WebEvent<Rectangle2D>>> onResizedProperty

      JavaScript window resize handler property. This handler is invoked when a script running on the Web page moves or resizes the `window` object.
      See Also:
        `getOnResized()`, `setOnResized(EventHandler)`

    - #### onVisibilityChanged

          public final ObjectProperty<EventHandler<WebEvent<Boolean>>> onVisibilityChangedProperty

      JavaScript window visibility handler property. This handler is invoked when a script running on the Web page changes visibility of the `window` object.
      See Also:
        `getOnVisibilityChanged()`, `setOnVisibilityChanged(EventHandler)`

    - #### createPopupHandler

          public final ObjectProperty<Callback<PopupFeatures,​WebEngine>> createPopupHandlerProperty

      JavaScript popup handler property. This handler is invoked when a script running on the Web page requests a popup to be created.

      To satisfy this request a handler may create a new `WebEngine`, attach a visibility handler and optionally a resize handler, and return the newly created engine. To block the popup, a handler should return `null`.

      By default, a popup handler is installed that opens popups in this `WebEngine`.

      See Also:
        `getCreatePopupHandler()`, `setCreatePopupHandler(Callback)`

    - #### confirmHandler

          public final ObjectProperty<Callback<String,​Boolean>> confirmHandlerProperty

      JavaScript `confirm` handler property. This handler is invoked when a script running on the Web page calls the `confirm` function.

      An implementation may display a dialog box with Yes and No options, and return the user's choice.

      See Also:
        `getConfirmHandler()`, `setConfirmHandler(Callback)`

    - #### promptHandler

          public final ObjectProperty<Callback<PromptData,​String>> promptHandlerProperty

      JavaScript `prompt` handler property. This handler is invoked when a script running on the Web page calls the `prompt` function.

      An implementation may display a dialog box with an text field, and return the user's input.

      See Also:
        `getPromptHandler()`, `setPromptHandler(Callback)`

    - #### onError

          public final ObjectProperty<EventHandler<WebErrorEvent>> onErrorProperty

      The event handler called when an error occurs.
      Default value:
        `null`
      Since:
        JavaFX 8.0
      See Also:
        `getOnError()`, `setOnError(EventHandler)`

  - ### Constructor Detail

    - #### WebEngine

          public WebEngine()

      Creates a new engine.

    - #### WebEngine

          public WebEngine​(String url)

      Creates a new engine and loads a Web page into it.
      Parameters:
        `url` - the URL of the web page to load

  - ### Method Detail

    - #### getLoadWorker

          public final Worker<Void> getLoadWorker()

      Returns a `Worker` object that can be used to track loading progress.
      Returns:
        the `Worker` object

    - #### getDocument

          public final Document getDocument()

      Gets the value of the property document.
      Property description:
        Document object for the current Web page. The value is `null` if the Web page failed to load.

    - #### documentProperty

          public final ReadOnlyObjectProperty<Document> documentProperty()

      Document object for the current Web page. The value is `null` if the Web page failed to load.
      See Also:
        `getDocument()`

    - #### getLocation

          public final String getLocation()

      Gets the value of the property location.
      Property description:
        URL of the current Web page. If the current page has no URL, the value is an empty String.

    - #### locationProperty

          public final ReadOnlyStringProperty locationProperty()

      URL of the current Web page. If the current page has no URL, the value is an empty String.
      See Also:
        `getLocation()`

    - #### getTitle

          public final String getTitle()

      Gets the value of the property title.
      Property description:
        Title of the current Web page. If the current page has no title, the value is `null`.

    - #### titleProperty

          public final ReadOnlyStringProperty titleProperty()

      Title of the current Web page. If the current page has no title, the value is `null`.
      See Also:
        `getTitle()`

    - #### setJavaScriptEnabled

          public final void setJavaScriptEnabled​(boolean value)

      Sets the value of the property javaScriptEnabled.
      Property description:
        Specifies whether JavaScript execution is enabled.
      Default value:
        true
      Since:
        JavaFX 2.2

    - #### isJavaScriptEnabled

          public final boolean isJavaScriptEnabled()

      Gets the value of the property javaScriptEnabled.
      Property description:
        Specifies whether JavaScript execution is enabled.
      Default value:
        true
      Since:
        JavaFX 2.2

    - #### javaScriptEnabledProperty

          public final BooleanProperty javaScriptEnabledProperty()

      Specifies whether JavaScript execution is enabled.
      Default value:
        true
      Since:
        JavaFX 2.2
      See Also:
        `isJavaScriptEnabled()`, `setJavaScriptEnabled(boolean)`

    - #### setUserStyleSheetLocation

          public final void setUserStyleSheetLocation​(String value)

      Sets the value of the property userStyleSheetLocation.
      Property description:
        Location of the user stylesheet as a string URL.

        This should be a local URL, i.e. either `'data:'`, `'file:'`, or `'jar:'`. Remote URLs are not allowed for security reasons.

      Default value:
        null
      Since:
        JavaFX 2.2

    - #### getUserStyleSheetLocation

          public final String getUserStyleSheetLocation()

      Gets the value of the property userStyleSheetLocation.
      Property description:
        Location of the user stylesheet as a string URL.

        This should be a local URL, i.e. either `'data:'`, `'file:'`, or `'jar:'`. Remote URLs are not allowed for security reasons.

      Default value:
        null
      Since:
        JavaFX 2.2

    - #### userStyleSheetLocationProperty

          public final StringProperty userStyleSheetLocationProperty()

      Location of the user stylesheet as a string URL.

      This should be a local URL, i.e. either `'data:'`, `'file:'`, or `'jar:'`. Remote URLs are not allowed for security reasons.

      Default value:
        null
      Since:
        JavaFX 2.2
      See Also:
        `getUserStyleSheetLocation()`, `setUserStyleSheetLocation(String)`

    - #### getUserDataDirectory

          public final File getUserDataDirectory()

      Gets the value of the property userDataDirectory.
      Property description:
        Specifies the directory to be used by this `WebEngine` to store local user data.

        If the value of this property is not `null`, the `WebEngine` will attempt to store local user data in the respective directory. If the value of this property is `null`, the `WebEngine` will attempt to store local user data in an automatically selected system-dependent user- and application-specific directory.

        When a `WebEngine` is about to start loading a web page or executing a script for the first time, it checks whether it can actually use the directory specified by this property. If the check fails for some reason, the `WebEngine` invokes the `WebEngine.onError` event handler, if any, with a `WebErrorEvent` describing the reason. If the invoked event handler modifies the `userDataDirectory` property, the `WebEngine` retries with the new value as soon as the handler returns. If the handler does not modify the `userDataDirectory` property (which is the default), the `WebEngine` continues without local user data.

        Once the `WebEngine` has started loading a web page or executing a script, changes made to this property have no effect on where the `WebEngine` stores or will store local user data.

        Currently, the directory specified by this property is used only to store the data that backs the `window.localStorage` objects. In the future, more types of data can be added.

      Default value:
        `null`
      Since:
        JavaFX 8.0

    - #### setUserDataDirectory

          public final void setUserDataDirectory​(File value)

      Sets the value of the property userDataDirectory.
      Property description:
        Specifies the directory to be used by this `WebEngine` to store local user data.

        If the value of this property is not `null`, the `WebEngine` will attempt to store local user data in the respective directory. If the value of this property is `null`, the `WebEngine` will attempt to store local user data in an automatically selected system-dependent user- and application-specific directory.

        When a `WebEngine` is about to start loading a web page or executing a script for the first time, it checks whether it can actually use the directory specified by this property. If the check fails for some reason, the `WebEngine` invokes the `WebEngine.onError` event handler, if any, with a `WebErrorEvent` describing the reason. If the invoked event handler modifies the `userDataDirectory` property, the `WebEngine` retries with the new value as soon as the handler returns. If the handler does not modify the `userDataDirectory` property (which is the default), the `WebEngine` continues without local user data.

        Once the `WebEngine` has started loading a web page or executing a script, changes made to this property have no effect on where the `WebEngine` stores or will store local user data.

        Currently, the directory specified by this property is used only to store the data that backs the `window.localStorage` objects. In the future, more types of data can be added.

      Default value:
        `null`
      Since:
        JavaFX 8.0

    - #### userDataDirectoryProperty

          public final ObjectProperty<File> userDataDirectoryProperty()

      Specifies the directory to be used by this `WebEngine` to store local user data.

      If the value of this property is not `null`, the `WebEngine` will attempt to store local user data in the respective directory. If the value of this property is `null`, the `WebEngine` will attempt to store local user data in an automatically selected system-dependent user- and application-specific directory.

      When a `WebEngine` is about to start loading a web page or executing a script for the first time, it checks whether it can actually use the directory specified by this property. If the check fails for some reason, the `WebEngine` invokes the `WebEngine.onError` event handler, if any, with a `WebErrorEvent` describing the reason. If the invoked event handler modifies the `userDataDirectory` property, the `WebEngine` retries with the new value as soon as the handler returns. If the handler does not modify the `userDataDirectory` property (which is the default), the `WebEngine` continues without local user data.

      Once the `WebEngine` has started loading a web page or executing a script, changes made to this property have no effect on where the `WebEngine` stores or will store local user data.

      Currently, the directory specified by this property is used only to store the data that backs the `window.localStorage` objects. In the future, more types of data can be added.

      Default value:
        `null`
      Since:
        JavaFX 8.0
      See Also:
        `getUserDataDirectory()`, `setUserDataDirectory(File)`

    - #### setUserAgent

          public final void setUserAgent​(String value)

      Sets the value of the property userAgent.
      Property description:
        Specifies user agent ID string. This string is the value of the `User-Agent` HTTP header.
      Default value:
        system dependent
      Since:
        JavaFX 8.0

    - #### getUserAgent

          public final String getUserAgent()

      Gets the value of the property userAgent.
      Property description:
        Specifies user agent ID string. This string is the value of the `User-Agent` HTTP header.
      Default value:
        system dependent
      Since:
        JavaFX 8.0

    - #### userAgentProperty

          public final StringProperty userAgentProperty()

      Specifies user agent ID string. This string is the value of the `User-Agent` HTTP header.
      Default value:
        system dependent
      Since:
        JavaFX 8.0
      See Also:
        `getUserAgent()`, `setUserAgent(String)`

    - #### getOnAlert

          public final EventHandler<WebEvent<String>> getOnAlert()

      Gets the value of the property onAlert.
      Property description:
        JavaScript `alert` handler property. This handler is invoked when a script running on the Web page calls the `alert` function.

    - #### setOnAlert

          public final void setOnAlert​(EventHandler<WebEvent<String>> handler)

      Sets the value of the property onAlert.
      Property description:
        JavaScript `alert` handler property. This handler is invoked when a script running on the Web page calls the `alert` function.

    - #### onAlertProperty

          public final ObjectProperty<EventHandler<WebEvent<String>>> onAlertProperty()

      JavaScript `alert` handler property. This handler is invoked when a script running on the Web page calls the `alert` function.
      See Also:
        `getOnAlert()`, `setOnAlert(EventHandler)`

    - #### getOnStatusChanged

          public final EventHandler<WebEvent<String>> getOnStatusChanged()

      Gets the value of the property onStatusChanged.
      Property description:
        JavaScript status handler property. This handler is invoked when a script running on the Web page sets `window.status` property.

    - #### setOnStatusChanged

          public final void setOnStatusChanged​(EventHandler<WebEvent<String>> handler)

      Sets the value of the property onStatusChanged.
      Property description:
        JavaScript status handler property. This handler is invoked when a script running on the Web page sets `window.status` property.

    - #### onStatusChangedProperty

          public final ObjectProperty<EventHandler<WebEvent<String>>> onStatusChangedProperty()

      JavaScript status handler property. This handler is invoked when a script running on the Web page sets `window.status` property.
      See Also:
        `getOnStatusChanged()`, `setOnStatusChanged(EventHandler)`

    - #### getOnResized

          public final EventHandler<WebEvent<Rectangle2D>> getOnResized()

      Gets the value of the property onResized.
      Property description:
        JavaScript window resize handler property. This handler is invoked when a script running on the Web page moves or resizes the `window` object.

    - #### setOnResized

          public final void setOnResized​(EventHandler<WebEvent<Rectangle2D>> handler)

      Sets the value of the property onResized.
      Property description:
        JavaScript window resize handler property. This handler is invoked when a script running on the Web page moves or resizes the `window` object.

    - #### onResizedProperty

          public final ObjectProperty<EventHandler<WebEvent<Rectangle2D>>> onResizedProperty()

      JavaScript window resize handler property. This handler is invoked when a script running on the Web page moves or resizes the `window` object.
      See Also:
        `getOnResized()`, `setOnResized(EventHandler)`

    - #### getOnVisibilityChanged

          public final EventHandler<WebEvent<Boolean>> getOnVisibilityChanged()

      Gets the value of the property onVisibilityChanged.
      Property description:
        JavaScript window visibility handler property. This handler is invoked when a script running on the Web page changes visibility of the `window` object.

    - #### setOnVisibilityChanged

          public final void setOnVisibilityChanged​(EventHandler<WebEvent<Boolean>> handler)

      Sets the value of the property onVisibilityChanged.
      Property description:
        JavaScript window visibility handler property. This handler is invoked when a script running on the Web page changes visibility of the `window` object.

    - #### onVisibilityChangedProperty

          public final ObjectProperty<EventHandler<WebEvent<Boolean>>> onVisibilityChangedProperty()

      JavaScript window visibility handler property. This handler is invoked when a script running on the Web page changes visibility of the `window` object.
      See Also:
        `getOnVisibilityChanged()`, `setOnVisibilityChanged(EventHandler)`

    - #### getCreatePopupHandler

          public final Callback<PopupFeatures,​WebEngine> getCreatePopupHandler()

      Gets the value of the property createPopupHandler.
      Property description:
        JavaScript popup handler property. This handler is invoked when a script running on the Web page requests a popup to be created.

        To satisfy this request a handler may create a new `WebEngine`, attach a visibility handler and optionally a resize handler, and return the newly created engine. To block the popup, a handler should return `null`.

        By default, a popup handler is installed that opens popups in this `WebEngine`.

    - #### setCreatePopupHandler

          public final void setCreatePopupHandler​(Callback<PopupFeatures,​WebEngine> handler)

      Sets the value of the property createPopupHandler.
      Property description:
        JavaScript popup handler property. This handler is invoked when a script running on the Web page requests a popup to be created.

        To satisfy this request a handler may create a new `WebEngine`, attach a visibility handler and optionally a resize handler, and return the newly created engine. To block the popup, a handler should return `null`.

        By default, a popup handler is installed that opens popups in this `WebEngine`.

    - #### createPopupHandlerProperty

          public final ObjectProperty<Callback<PopupFeatures,​WebEngine>> createPopupHandlerProperty()

      JavaScript popup handler property. This handler is invoked when a script running on the Web page requests a popup to be created.

      To satisfy this request a handler may create a new `WebEngine`, attach a visibility handler and optionally a resize handler, and return the newly created engine. To block the popup, a handler should return `null`.

      By default, a popup handler is installed that opens popups in this `WebEngine`.

      See Also:
        `getCreatePopupHandler()`, `setCreatePopupHandler(Callback)`

    - #### getConfirmHandler

          public final Callback<String,​Boolean> getConfirmHandler()

      Gets the value of the property confirmHandler.
      Property description:
        JavaScript `confirm` handler property. This handler is invoked when a script running on the Web page calls the `confirm` function.

        An implementation may display a dialog box with Yes and No options, and return the user's choice.

    - #### setConfirmHandler

          public final void setConfirmHandler​(Callback<String,​Boolean> handler)

      Sets the value of the property confirmHandler.
      Property description:
        JavaScript `confirm` handler property. This handler is invoked when a script running on the Web page calls the `confirm` function.

        An implementation may display a dialog box with Yes and No options, and return the user's choice.

    - #### confirmHandlerProperty

          public final ObjectProperty<Callback<String,​Boolean>> confirmHandlerProperty()

      JavaScript `confirm` handler property. This handler is invoked when a script running on the Web page calls the `confirm` function.

      An implementation may display a dialog box with Yes and No options, and return the user's choice.

      See Also:
        `getConfirmHandler()`, `setConfirmHandler(Callback)`

    - #### getPromptHandler

          public final Callback<PromptData,​String> getPromptHandler()

      Gets the value of the property promptHandler.
      Property description:
        JavaScript `prompt` handler property. This handler is invoked when a script running on the Web page calls the `prompt` function.

        An implementation may display a dialog box with an text field, and return the user's input.

    - #### setPromptHandler

          public final void setPromptHandler​(Callback<PromptData,​String> handler)

      Sets the value of the property promptHandler.
      Property description:
        JavaScript `prompt` handler property. This handler is invoked when a script running on the Web page calls the `prompt` function.

        An implementation may display a dialog box with an text field, and return the user's input.

    - #### promptHandlerProperty

          public final ObjectProperty<Callback<PromptData,​String>> promptHandlerProperty()

      JavaScript `prompt` handler property. This handler is invoked when a script running on the Web page calls the `prompt` function.

      An implementation may display a dialog box with an text field, and return the user's input.

      See Also:
        `getPromptHandler()`, `setPromptHandler(Callback)`

    - #### getOnError

          public final EventHandler<WebErrorEvent> getOnError()

      Gets the value of the property onError.
      Property description:
        The event handler called when an error occurs.
      Default value:
        `null`
      Since:
        JavaFX 8.0

    - #### setOnError

          public final void setOnError​(EventHandler<WebErrorEvent> handler)

      Sets the value of the property onError.
      Property description:
        The event handler called when an error occurs.
      Default value:
        `null`
      Since:
        JavaFX 8.0

    - #### onErrorProperty

          public final ObjectProperty<EventHandler<WebErrorEvent>> onErrorProperty()

      The event handler called when an error occurs.
      Default value:
        `null`
      Since:
        JavaFX 8.0
      See Also:
        `getOnError()`, `setOnError(EventHandler)`

    - #### load

          public void load​(String url)

      Loads a Web page into this engine. This method starts asynchronous loading and returns immediately.
      Parameters:
        `url` - URL of the web page to load

    - #### loadContent

          public void loadContent​(String content)

      Loads the given HTML content directly. This method is useful when you have an HTML String composed in memory, or loaded from some system which cannot be reached via a URL (for example, the HTML text may have come from a database). As with `load(String)`, this method is asynchronous.
      Parameters:
        `content` - the HTML content to load

    - #### loadContent

          public void loadContent​(String content,
                                  String contentType)

      Loads the given content directly. This method is useful when you have content composed in memory, or loaded from some system which cannot be reached via a URL (for example, the SVG text may have come from a database). As with `load(String)`, this method is asynchronous. This method also allows you to specify the content type of the string being loaded, and so may optionally support other types besides just HTML.
      Parameters:
        `content` - the HTML content to load
        `contentType` - the type of content to load

    - #### reload

          public void reload()

      Reloads the current page, whether loaded from URL or directly from a String in one of the `loadContent` methods.

    - #### getHistory

          public WebHistory getHistory()

      Returns the session history object.
      Returns:
        history object
      Since:
        JavaFX 2.2

    - #### executeScript

          public Object executeScript​(String script)

      Executes a script in the context of the current page.
      Parameters:
        `script` - the script
      Returns:
        execution result, converted to a Java object using the following rules:
        - JavaScript Int32 is converted to `java.lang.Integer`
        - Other JavaScript numbers to `java.lang.Double`
        - JavaScript string to `java.lang.String`
        - JavaScript boolean to `java.lang.Boolean`
        - JavaScript `null` to `null`
        - Most JavaScript objects get wrapped as `netscape.javascript.JSObject`
        - JavaScript JSNode objects get mapped to instances of `netscape.javascript.JSObject`, that also implement `org.w3c.dom.Node`
        - A special case is the JavaScript class `JavaRuntimeObject` which is used to wrap a Java object as a JavaScript value - in this case we just extract the original Java value.

    - #### print

          public void print​(PrinterJob job)

      Prints the current Web page using the given printer job.

      This method does not modify the state of the job, nor does it call `PrinterJob.endJob()`, so the job may be safely reused afterwards.

      Parameters:
        `job` - printer job used for printing
      Since:
        JavaFX 8.0