com.vaadin.server

Class FileDownloader

java.lang.Object

com.vaadin.server.AbstractClientConnector

com.vaadin.server.AbstractExtension

com.vaadin.server.FileDownloader

All Implemented Interfaces:

MethodEventSource, ClientConnector, Extension, Connector, Serializable

public class FileDownloader
extends AbstractExtension

Extension that starts a download when the extended component is clicked. This is used to overcome two challenges:

• Resource should be bound to a component to allow it to be garbage collected when there are no longer any ways of reaching the resource.
• Download should be started directly when the user clicks e.g. a Button without going through a server-side click listener to avoid triggering security warnings in some browsers.

Please note that the download will be started in an iframe, which means that care should be taken to avoid serving content types that might make the browser attempt to show the content using a plugin instead of downloading it. Connector resources (e.g. FileResource and ClassResource) will automatically be served using a Content-Type: application/octet-stream header unless setOverrideContentType(boolean) has been set to false while files served in other ways, (e.g. ExternalResource or ThemeResource) will not automatically get this treatment.

Since:

7.0.0

Author:

Vaadin Ltd

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from interface com.vaadin.server.ClientConnector

ClientConnector.AttachEvent, ClientConnector.AttachListener, ClientConnector.ConnectorErrorEvent, ClientConnector.DetachEvent, ClientConnector.DetachListener

Constructor Summary

Constructors

Constructor and Description
FileDownloader(Resource resource) Creates a new file downloader for the given resource.

Method Summary

Modifier and Type	Method and Description
void	extend(AbstractComponent target) Add this extension to the target component.
void	extend(EventTrigger eventTrigger) Add this extension to the EventTrigger.
Resource	getFileDownloadResource() Gets the resource set for download.
protected FileDownloaderState	getState() Returns the shared state for this connector.
protected FileDownloaderState	getState(boolean markAsDirty) Returns the shared state for this connector.
boolean	handleConnectorRequest(VaadinRequest request, VaadinResponse response, String path) Handle a request directed to this connector.
boolean	isOverrideContentType() Checks whether the content type should be overridden.
void	setFileDownloadResource(Resource resource) Sets the resource that is downloaded when the extended component is clicked.
void	setOverrideContentType(boolean overrideContentType) Sets whether the content type of served resources should be overridden to application/octet-stream to reduce the risk of a browser plugin choosing to display the resource instead of downloading it.

Methods inherited from class com.vaadin.server.AbstractExtension

extend, getParent, getSupportedParentType, remove, setParent

Methods inherited from class com.vaadin.server.AbstractClientConnector

addAttachListener, addDetachListener, addExtension, addListener, addListener, addListener, addMethodInvocationToQueue, attach, beforeClientResponse, createState, detach, encodeState, equals, fireEvent, getAllChildrenIterable, getConnectorId, getErrorHandler, getExtensions, getListeners, getResource, getRpcManager, getRpcProxy, getSession, getStateType, getUI, hashCode, hasListeners, isAttached, isConnectorEnabled, isThis, markAsDirty, markAsDirtyRecursive, registerRpc, registerRpc, removeAttachListener, removeDetachListener, removeExtension, removeListener, removeListener, removeListener, removeListener, requestRepaint, requestRepaintAll, retrievePendingRpcCalls, setErrorHandler, setResource, updateDiffstate

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface com.vaadin.server.ClientConnector

addAttachListener, addDetachListener, attach, beforeClientResponse, detach, encodeState, getErrorHandler, getExtensions, getRpcManager, getStateType, getUI, isAttached, isConnectorEnabled, markAsDirty, markAsDirtyRecursive, removeAttachListener, removeDetachListener, removeExtension, requestRepaint, requestRepaintAll, retrievePendingRpcCalls, setErrorHandler

Methods inherited from interface com.vaadin.shared.Connector

getConnectorId

Constructor Detail

FileDownloader

public FileDownloader(Resource resource)

Creates a new file downloader for the given resource. To use the downloader, you should also AbstractExtension.extend(AbstractClientConnector) the component.

Parameters:

resource - the resource to download when the user clicks the extended component.

Method Detail

extend

public void extend(AbstractComponent target)

Add this extension to the target component.

Parameters:

target - the component to attach this extension to

extend

public void extend(EventTrigger eventTrigger)

Add this extension to the EventTrigger.

Parameters:

eventTrigger - the trigger to attach this extension to

Since:

8.4

getFileDownloadResource

public Resource getFileDownloadResource()

Gets the resource set for download.

Returns:

the resource that will be downloaded if clicking the extended component

setFileDownloadResource

public void setFileDownloadResource(Resource resource)

Sets the resource that is downloaded when the extended component is clicked.

Parameters:

resource - the resource to download

setOverrideContentType

public void setOverrideContentType(boolean overrideContentType)

Sets whether the content type of served resources should be overridden to application/octet-stream to reduce the risk of a browser plugin choosing to display the resource instead of downloading it. This is by default set to true.

Please note that this only affects Connector resources (e.g. FileResource and ClassResource) but not other resource types (e.g. ExternalResource or ThemeResource).

Parameters:

overrideContentType - true to override the content type if possible; false to use the original content type.

isOverrideContentType

public boolean isOverrideContentType()

Checks whether the content type should be overridden.

Returns:

true if the content type will be overridden when possible; false if the original content type will be used.

See Also:

setOverrideContentType(boolean)

handleConnectorRequest

public boolean handleConnectorRequest(VaadinRequest request,
                                      VaadinResponse response,
                                      String path)
                               throws IOException

Handle a request directed to this connector. This can be used by connectors to dynamically generate a response and it is also used internally when serving ConnectorResources.

Requests to /APP/connector/[ui id]/[connector id]/ are routed to this method with the remaining part of the requested path available in the path parameter.

NOTE that the session is not locked when this method is called. It is the responsibility of the connector to ensure that the session is locked while handling state or other session related data. For best performance the session should be unlocked before writing a large response to the client.

Specified by:

handleConnectorRequest in interface ClientConnector

Overrides:

handleConnectorRequest in class AbstractClientConnector

Parameters:

request - the request that should be handled

response - the response object to which the response should be written

path - the requested relative path

Returns:

true if the request has been handled, false if no response has been written.

Throws:

IOException - if something goes wrong with the download or the user cancelled the file download process.

getState

protected FileDownloaderState getState()

Description copied from class: AbstractClientConnector

Returns the shared state for this connector. The shared state object is shared between the server connector and the client connector. Changes are only communicated from the server to the client and not in the other direction.

As a side effect, marks the connector dirty so any changes done to the state will be sent to the client. Use getState(false) to avoid marking the connector as dirty.

Overrides:

getState in class AbstractClientConnector

Returns:

The shared state for this connector. Never null.

getState

protected FileDownloaderState getState(boolean markAsDirty)

Description copied from class: AbstractClientConnector

Returns the shared state for this connector.

Overrides:

getState in class AbstractClientConnector

Parameters:

markAsDirty - true if the connector should automatically be marked dirty, false otherwise

Returns:

The shared state for this connector. Never null.

See Also:

AbstractClientConnector.getState()