Class WResource

java.lang.Object
eu.webtoolkit.jwt.WObject
eu.webtoolkit.jwt.WResource
Direct Known Subclasses:
OAuthTokenEndpoint, OidcUserInfoEndpoint, WFileResource, WMemoryResource, WPdfImage, WRasterPaintDevice, WSvgImage

public abstract class WResource
extends WObject
An object which can be rendered in the HTTP protocol.

Usage

Besides the main page, other objects may be rendered as additional resources, for example documents or images. Classes such as WAnchor or WImage can use a resource instead of a URL to provide their contents. Whenever the resource has changed, you should call the setChanged() method. setChanged() will make sure that the browser will use a new version of the resource by generating a new URL, and emits the dataChanged() signal to make those that refer to the resource aware that they should update their references to the new URL.

You can help the browser to start a suitable helper application to handle the resource, or suggest to the user a suitable filename for saving the resource, by setting an appropriate file name using suggestFileName(String).

To serve resources that you create on the fly, you need to specialize this class and reimplement handleRequest(WebRequest, WebResponse).

Concurrency issues

Because of the nature of the web, a resource may be requested one time or multiple times at the discretion of the browser, and therefore your resource should in general not have any side-effects except for what is needed to render its own contents. Unlike event notifications to a JWt application, resource requests are not serialized, but are handled concurrently. Therefore you are not allowed to access or modify widget state from within the resource, unless you provide your own locking mechanism for it.
See Also:
WAnchor, WImage
  • Nested Class Summary

    Nested Classes 
    Modifier and Type Class Description
    static class  WResource.DispositionType
    Values for the disposition type in the Content-Disposition header

    Nested classes/interfaces inherited from class eu.webtoolkit.jwt.WObject

    WObject.FormData
  • Constructor Summary

    Constructors 
    Modifier Constructor Description
      WResource()
    Constructor.
    protected WResource​(WObject parent)  
  • Method Summary

    Modifier and Type Method Description
    Signal dataChanged()
    Signal triggered when the data presented in this resource has changed.
    Signal1<java.lang.Long> dataExceeded()  
    Signal2<java.lang.Long,​java.lang.Long> dataReceived()
    Signal emitted when data has been received for this resource.
    java.lang.String generateUrl()
    Generates a URL for this resource.
    WResource.DispositionType getDispositionType()
    Returns the currently configured content disposition
    java.lang.String getInternalPath()
    Returns the internal path.
    java.lang.String getSuggestedFileName()
    Returns the suggested file name.
    java.lang.String getUrl()
    Returns the current URL for this resource.
    protected abstract void handleRequest​(WebRequest request, WebResponse response)
    Handles a request.
    void setChanged()
    Generates a new URL for this resource and emits the changed signal
    void setDispositionType​(WResource.DispositionType dispositionType)
    Configures the Content-Disposition header The Content-Disposition header allows to instruct the browser that a resource should be shown inline or as attachment.
    void setInternalPath​(java.lang.String internalPath)
    Sets an internal path for this resource.
    void setTakesUpdateLock​(boolean enabled)
    Set whether this resource takes the WApplication's update lock.
    void setUploadProgress​(boolean enabled)
    Indicate interest in upload progress.
    void suggestFileName​(java.lang.String name)
    Suggests a filename to the user for the data streamed by this resource.
    void suggestFileName​(java.lang.String name, WResource.DispositionType dispositionType)
    Suggests a filename to the user for the data streamed by this resource.
    boolean takesUpdateLock()
    Get whether this resource takes the WApplication's update lock
    void write​(java.io.OutputStream out)
    Writes the resource to an output stream.
    void write​(java.io.OutputStream out, java.util.Map<java.lang.String,​java.lang.String[]> parameterMap, java.util.Map<java.lang.String,​java.util.List<UploadedFile>> uploadedFiles)
    Writes the resource to an output stream.

    Methods inherited from class eu.webtoolkit.jwt.WObject

    addChild, getId, getObjectName, remove, setFormData, setObjectName, tr

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
  • Constructor Details

  • Method Details

    • generateUrl

      public java.lang.String generateUrl()
      Generates a URL for this resource.

      The url is unique to assure that it is not cached by the web browser, and can thus be used to refer to a new "version" of the resource, which can be indicated by triggering the dataChanged() signal. The old urls are not invalidated by calling this method.

      Returns:
      the url.
    • handleRequest

      protected abstract void handleRequest​(WebRequest request, WebResponse response) throws java.io.IOException
      Handles a request.

      Reimplement this method so that a proper response is generated for the given request. From the request object you can access request parameters and whether the request is a continuation request. In the response object, you should set the mime type and stream the output data.

      Parameters:
      request - The request information
      response - The response object
      Throws:
      java.io.IOException
    • dataChanged

      public Signal dataChanged()
      Signal triggered when the data presented in this resource has changed.

      Widgets that reference the resource (such as anchors and images) will make sure the new data is rendered. It is better to call setChanged() than to trigger this signal since that method generates a new URL for this resource to avoid caching problems before emitting the signal.

    • write

      public void write​(java.io.OutputStream out, java.util.Map<java.lang.String,​java.lang.String[]> parameterMap, java.util.Map<java.lang.String,​java.util.List<UploadedFile>> uploadedFiles) throws java.io.IOException
      Writes the resource to an output stream.

      This is a utility method that allows you to write the resource to an output stream, by using handleRequest(WebRequest, WebResponse).

      Parameters:
      out - The output stream.
      parameterMap - A map with parameters that are made available in the WebRequest.
      uploadedFiles - A list of uploaded files that are made available in the WebRequest.
      Throws:
      java.io.IOException
    • write

      public void write​(java.io.OutputStream out) throws java.io.IOException
      Writes the resource to an output stream.

      This is a utility method that allows you to write the resource to an output stream, by using handleRequest(WebRequest, WebResponse).

      Parameters:
      out - The output stream.
      Throws:
      java.io.IOException
    • suggestFileName

      public void suggestFileName​(java.lang.String name, WResource.DispositionType dispositionType)
      Suggests a filename to the user for the data streamed by this resource.

      For resources, intended to be downloaded by the user, suggest a name used for saving. The filename extension may also help the browser to identify the correct program for opening the resource. The disposition type determines if the resource is intended to be opened by a plugin in the browser (DispositionType#Inline), or to be saved to disk (DispositionType#Attachment). DispositionType#NoDisposition is not a valid Content-Disposition when a filename is suggested; this will be rendered as DispositionType#Attachment.

      See Also:
      setDispositionType(DispositionType dispositionType)
    • suggestFileName

      public void suggestFileName​(java.lang.String name)
      Suggests a filename to the user for the data streamed by this resource.

      For resources, intended to be downloaded by the user, suggest a name used for saving. The filename extension may also help the browser to identify the correct program for opening the resource. The disposition type determines if the resource is intended to be opened by a plugin in the browser (DispositionType#Inline), or to be saved to disk (DispositionType#Attachment). DispositionType#NoDisposition is not a valid Content-Disposition when a filename is suggested; this will be rendered as DispositionType#Attachment.

      See Also:
      Calls
    • getSuggestedFileName

      public java.lang.String getSuggestedFileName()
      Returns the suggested file name.
      See Also:
      suggestFileName(String)
    • setChanged

      public void setChanged()
      Generates a new URL for this resource and emits the changed signal
    • setDispositionType

      public void setDispositionType​(WResource.DispositionType dispositionType)
      Configures the Content-Disposition header The Content-Disposition header allows to instruct the browser that a resource should be shown inline or as attachment. This function enables you to set this property. This is often used in combination with suggestFileName(String, DispositionType). The Content-Disposition must not be DispositionType#NoDisposition when a filename is given; if this case is encountered, None will be rendered as DispositionType#Attachment.
      See Also:
      suggestFileName(String, DispositionType)
    • getDispositionType

      public WResource.DispositionType getDispositionType()
      Returns the currently configured content disposition
      See Also:
      setDispositionType(DispositionType cd)
    • getUrl

      public java.lang.String getUrl()
      Returns the current URL for this resource. Returns the url that refers to this resource.
    • getInternalPath

      public java.lang.String getInternalPath()
      Returns the internal path.
      See Also:
      setInternalPath(String)
    • setInternalPath

      public void setInternalPath​(java.lang.String internalPath)
      Sets an internal path for this resource. Using this method you can deploy the resource at a fixed path. Unless you deploy using cookies for session tracking (not recommended), a session identifier will be appended to the path. You should use internal paths that are different from internal paths handled by your application (WApplication.setInternalPath(String)), if you do not want a conflict between these two when the browser does not use AJAX (and thus url fragments for its internal paths). The default value is empty. By default the URL for a resource is unspecified and a URL will be generated by the library.
    • setUploadProgress

      public void setUploadProgress​(boolean enabled)
      Indicate interest in upload progress. When supported, you can track upload progress using this signal. While data is being received, and before handleRequest(WebRequest request, WebResponse response) is called, progress information is indicated using dataReceived(). The default value is false.
    • setTakesUpdateLock

      public void setTakesUpdateLock​(boolean enabled)
      Set whether this resource takes the WApplication's update lock.

      By default, WResource takes the WApplication's update lock, so handleRequest() is performed in the WApplication's event loop.

      If necessary this can be disabled by setting this option to false. This will make it so that handleRequest() does not block the WApplication, and multiple handleRequest() calls can be performed concurrently.

      This option has no effect on static resources, since there is no WApplication in that case.

    • takesUpdateLock

      public boolean takesUpdateLock()
      Get whether this resource takes the WApplication's update lock
      See Also:
      setTakesUpdateLock(boolean)
    • dataReceived

      public Signal2<java.lang.Long,​java.lang.Long> dataReceived()
      Signal emitted when data has been received for this resource. When this signal is emitted, you have the update lock to modify the application. Because there is however no corresponding request from the browser, any update to the user interface is not immediately reflected in the client. To update the client interface, you need to use a WTimer.
      See Also:
      setUploadProgress(boolean enabled)
    • dataExceeded

      public Signal1<java.lang.Long> dataExceeded()