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Java™ Platform Standard Ed. 6 |
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java.lang.Object javax.activation.DataHandler
public class DataHandler
The DataHandler class provides a consistent interface to data available in many different sources and formats. It manages simple stream to string conversions and related operations using DataContentHandlers. It provides access to commands that can operate on the data. The commands are found using a CommandMap.
DataHandler and the Transferable Interface
DataHandler implements the Transferable interface so that data can be used in AWT data transfer operations, such as cut and paste and drag and drop. The implementation of the Transferable interface relies on the availability of an installed DataContentHandler object corresponding to the MIME type of the data represented in the specific instance of the DataHandler.
DataHandler and CommandMaps
The DataHandler keeps track of the current CommandMap that it uses to
service requests for commands (getCommand
,
getAllCommands
, getPreferredCommands
).
Each instance of a DataHandler may have a CommandMap associated with
it using the setCommandMap
method. If a CommandMap was
not set, DataHandler calls the getDefaultCommandMap
method in CommandMap and uses the value it returns. See
CommandMap for more information.
DataHandler and URLs
The current DataHandler implementation creates a private instance of URLDataSource when it is constructed with a URL.
CommandMap
,
DataContentHandler
,
DataSource
,
URLDataSource
Constructor Summary | |
---|---|
DataHandler(DataSource ds)
Create a DataHandler instance referencing the
specified DataSource. |
|
DataHandler(Object obj,
String mimeType)
Create a DataHandler instance representing an object
of this MIME type. |
|
DataHandler(URL url)
Create a DataHandler instance referencing a URL. |
Method Summary | |
---|---|
CommandInfo[] |
getAllCommands()
Return all the commands for this type of data. |
Object |
getBean(CommandInfo cmdinfo)
A convenience method that takes a CommandInfo object and instantiates the corresponding command, usually a JavaBean component. |
CommandInfo |
getCommand(String cmdName)
Get the command cmdName. |
Object |
getContent()
Return the data in its preferred Object form. |
String |
getContentType()
Return the MIME type of this object as retrieved from the source object. |
DataSource |
getDataSource()
Return the DataSource associated with this instance of DataHandler. |
InputStream |
getInputStream()
Get the InputStream for this object. |
String |
getName()
Return the name of the data object. |
OutputStream |
getOutputStream()
Get an OutputStream for this DataHandler to allow overwriting the underlying data. |
CommandInfo[] |
getPreferredCommands()
Return the preferred commands for this type of data. |
Object |
getTransferData(DataFlavor flavor)
Returns an object that represents the data to be transferred. |
DataFlavor[] |
getTransferDataFlavors()
Return the DataFlavors in which this data is available. |
boolean |
isDataFlavorSupported(DataFlavor flavor)
Returns whether the specified data flavor is supported for this object. |
void |
setCommandMap(CommandMap commandMap)
Set the CommandMap for use by this DataHandler. |
static void |
setDataContentHandlerFactory(DataContentHandlerFactory newFactory)
Sets the DataContentHandlerFactory. |
void |
writeTo(OutputStream os)
Write the data to an OutputStream . |
Methods inherited from class java.lang.Object |
---|
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
---|
public DataHandler(DataSource ds)
DataHandler
instance referencing the
specified DataSource. The data exists in a byte stream form.
The DataSource will provide an InputStream to access the data.
ds
- the DataSourcepublic DataHandler(Object obj, String mimeType)
DataHandler
instance representing an object
of this MIME type. This constructor is
used when the application already has an in-memory representation
of the data in the form of a Java Object.
obj
- the Java ObjectmimeType
- the MIME type of the objectpublic DataHandler(URL url)
DataHandler
instance referencing a URL.
The DataHandler internally creates a URLDataSource
instance to represent the URL.
url
- a URL objectMethod Detail |
---|
public DataSource getDataSource()
For DataHandlers that have been instantiated with a DataSource, this method returns the DataSource that was used to create the DataHandler object. In other cases the DataHandler constructs a DataSource from the data used to construct the DataHandler. DataSources created for DataHandlers not instantiated with a DataSource are cached for performance reasons.
public String getName()
DataSource.getName
method, otherwise it
returns null.
public String getContentType()
public InputStream getInputStream() throws IOException
For DataHandlers instantiated with a DataSource, the DataHandler
calls the DataSource.getInputStream
method and
returns the result to the caller.
For DataHandlers instantiated with an Object, the DataHandler
first attempts to find a DataContentHandler for the Object. If
the DataHandler can not find a DataContentHandler for this MIME
type, it throws an UnsupportedDataTypeException. If it is
successful, it creates a pipe and a thread. The thread uses the
DataContentHandler's writeTo
method to write the
stream data into one end of the pipe. The other end of the pipe
is returned to the caller. Because a thread is created to copy
the data, IOExceptions that may occur during the copy can not be
propagated back to the caller. The result is an empty stream.
IOException
- if an I/O error occursDataContentHandler.writeTo(java.lang.Object, java.lang.String, java.io.OutputStream)
,
UnsupportedDataTypeException
public void writeTo(OutputStream os) throws IOException
OutputStream
.If the DataHandler was created with a DataSource, writeTo retrieves the InputStream and copies the bytes from the InputStream to the OutputStream passed in.
If the DataHandler was created with an object, writeTo
retrieves the DataContentHandler for the object's type.
If the DataContentHandler was found, it calls the
writeTo
method on the DataContentHandler
.
os
- the OutputStream to write to
IOException
- if an I/O error occurspublic OutputStream getOutputStream() throws IOException
getOutputStream
method is called.
Otherwise, null
is returned.
IOException
DataSource.getOutputStream()
,
URLDataSource
public DataFlavor[] getTransferDataFlavors()
Returns an array of DataFlavor objects indicating the flavors the data can be provided in. The array is usually ordered according to preference for providing the data, from most richly descriptive to least richly descriptive.
The DataHandler attempts to find a DataContentHandler that
corresponds to the MIME type of the data. If one is located,
the DataHandler calls the DataContentHandler's
getTransferDataFlavors
method.
If a DataContentHandler can not be located, and if the
DataHandler was created with a DataSource (or URL), one
DataFlavor is returned that represents this object's MIME type
and the java.io.InputStream
class. If the
DataHandler was created with an object and a MIME type,
getTransferDataFlavors returns one DataFlavor that represents
this object's MIME type and the object's class.
getTransferDataFlavors
in interface Transferable
DataContentHandler.getTransferDataFlavors()
public boolean isDataFlavorSupported(DataFlavor flavor)
This method iterates through the DataFlavors returned from
getTransferDataFlavors
, comparing each with
the specified flavor.
isDataFlavorSupported
in interface Transferable
flavor
- the requested flavor for the data
getTransferDataFlavors()
public Object getTransferData(DataFlavor flavor) throws UnsupportedFlavorException, IOException
For DataHandler's created with DataSources or URLs:
The DataHandler attempts to locate a DataContentHandler
for this MIME type. If one is found, the passed in DataFlavor
and the type of the data are passed to its getTransferData
method. If the DataHandler fails to locate a DataContentHandler
and the flavor specifies this object's MIME type and the
java.io.InputStream
class, this object's InputStream
is returned.
Otherwise it throws an UnsupportedFlavorException.
For DataHandler's created with Objects:
The DataHandler attempts to locate a DataContentHandler for this MIME type. If one is found, the passed in DataFlavor and the type of the data are passed to its getTransferData method. If the DataHandler fails to locate a DataContentHandler and the flavor specifies this object's MIME type and its class, this DataHandler's referenced object is returned. Otherwise it throws an UnsupportedFlavorException.
getTransferData
in interface Transferable
flavor
- the requested flavor for the data
UnsupportedFlavorException
- if the data could not be
converted to the requested flavor
IOException
- if an I/O error occursActivationDataFlavor
public void setCommandMap(CommandMap commandMap)
null
causes the CommandMap to revert
to the CommandMap returned by the
CommandMap.getDefaultCommandMap
method.
Changing the CommandMap, or setting it to null
,
clears out any data cached from the previous CommandMap.
commandMap
- the CommandMap to use in this DataHandlerCommandMap.setDefaultCommandMap(javax.activation.CommandMap)
public CommandInfo[] getPreferredCommands()
getPreferredCommands
method
in the CommandMap associated with this instance of DataHandler.
This method returns an array that represents a subset of
available commands. In cases where multiple commands for the
MIME type represented by this DataHandler are present, the
installed CommandMap chooses the appropriate commands.
CommandMap.getPreferredCommands(java.lang.String)
public CommandInfo[] getAllCommands()
getAllCommands
method
of the CommandMap associated with this DataHandler.
CommandMap.getAllCommands(java.lang.String)
public CommandInfo getCommand(String cmdName)
getCommand
method
of the CommandMap associated with this DataHandler.
cmdName
- the command name
CommandMap.getCommand(java.lang.String, java.lang.String)
public Object getContent() throws IOException
If the DataHandler was instantiated with an object, return the object.
If the DataHandler was instantiated with a DataSource,
this method uses a DataContentHandler to return the content
object for the data represented by this DataHandler. If no
DataContentHandler
can be found for the
the type of this data, the DataHandler returns an
InputStream for the data.
IOException
- if an IOException occurs during
this operation.public Object getBean(CommandInfo cmdinfo)
This method calls the CommandInfo's getCommandObject
method with the ClassLoader
used to load
the javax.activation.DataHandler
class itself.
cmdinfo
- the CommandInfo corresponding to a command
public static void setDataContentHandlerFactory(DataContentHandlerFactory newFactory)
If the DataContentHandlerFactory has already been set, this method throws an Error.
newFactory
- the DataContentHandlerFactory
Error
- if the factory has already been defined.DataContentHandlerFactory
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Java™ Platform Standard Ed. 6 |
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