Class WResource
- Direct Known Subclasses:
OAuthTokenEndpoint
,OidcUserInfoEndpoint
,WFileResource
,WMemoryResource
,WPdfImage
,WRasterPaintDevice
,WSvgImage
Usage
Besides the main page, other objects may be rendered as additional resources, for example documents or images. Classes such asWAnchor
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.-
Nested Class Summary
Nested ClassesModifier and TypeClassDescriptionstatic enum
Values for the disposition type in the Content-Disposition headerNested classes/interfaces inherited from class eu.webtoolkit.jwt.WObject
WObject.FormData
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Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionSignal triggered when the data presented in this resource has changed.Signal emitted when data has been received for this resource.Generates a URL for this resource.Returns the currently configured content dispositionReturns the internal path.Returns the suggested file name.getUrl()
Returns the current URL for this resource.int
protected abstract void
handleRequest
(WebRequest request, WebResponse response) Handles a request.void
boolean
Should "page not found" be returned for outdated resource URLsvoid
Generates a new URL for this resource and emits the changed signalvoid
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
(String internalPath) Sets an internal path for this resource.void
setInvalidAfterChanged
(boolean enabled) Return "page not found" for prior resource URLs after change This option invalidates earlier versions of the resource url prior to the last call of setChanged() or generateUrl().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
(String name) Suggests a filename to the user for the data streamed by this resource.void
suggestFileName
(String name, WResource.DispositionType dispositionType) Suggests a filename to the user for the data streamed by this resource.boolean
Get whether this resource takes the WApplication's update lockvoid
write
(OutputStream out) Writes the resource to an output stream.void
write
(OutputStream out, Map<String, String[]> parameterMap, Map<String, List<UploadedFile>> uploadedFiles) Writes the resource to an output stream.Methods inherited from class eu.webtoolkit.jwt.WObject
getId, getObjectName, remove, setFormData, setObjectName, tr
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Constructor Details
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WResource
public WResource()Constructor.
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Method Details
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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, unless you enable setInvalidAfterChanged().- Returns:
- the url.
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handleRequest
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 informationresponse
- The response object- Throws:
IOException
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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(OutputStream out, Map<String, String[]> parameterMap, Map<String, throws IOExceptionList<UploadedFile>> uploadedFiles) 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 theWebRequest
.uploadedFiles
- A list of uploaded files that are made available in theWebRequest
.- Throws:
IOException
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write
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:
IOException
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suggestFileName
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.
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suggestFileName
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.
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getSuggestedFileName
Returns the suggested file name.- See Also:
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setChanged
public void setChanged()Generates a new URL for this resource and emits the changed signal- See Also:
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setInvalidAfterChanged
public void setInvalidAfterChanged(boolean enabled) Return "page not found" for prior resource URLs after change This option invalidates earlier versions of the resource url prior to the last call of setChanged() or generateUrl(). The default value is false. This does not work when the resource is deployed at an internal path using setInternalPath().- See Also:
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isInvalidAfterChanged
public boolean isInvalidAfterChanged()Should "page not found" be returned for outdated resource URLs- See Also:
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#setInvalidAfterChanged()
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setDispositionType
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 withsuggestFileName(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:
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getDispositionType
Returns the currently configured content disposition- See Also:
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getUrl
Returns the current URL for this resource. Returns the url that refers to this resource. -
getInternalPath
Returns the internal path.- See Also:
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setInternalPath
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 beforehandleRequest(WebRequest request, WebResponse response)
is called, progress information is indicated usingdataReceived()
. 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.
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takesUpdateLock
public boolean takesUpdateLock()Get whether this resource takes the WApplication's update lock- See Also:
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getVersion
public int getVersion() -
incrementVersion
public void incrementVersion() -
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 aWTimer
.- See Also:
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dataExceeded
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