java.awt.datatransfer
class DataFlavor

java.lang.Object java.awt.datatransfer.DataFlavor

All Implemented Interfaces:

Externalizable, Cloneable

public class DataFlavor
extends Object
implements Externalizable, Cloneable

A {@code DataFlavor} provides meta information about data. {@code DataFlavor} is typically used to access data on the clipboard, or during a drag and drop operation.

An instance of {@code DataFlavor} encapsulates a content type as defined in RFC 2045 and RFC 2046. A content type is typically referred to as a MIME type.

A content type consists of a media type (referred to as the primary type), a subtype, and optional parameters. See RFC 2045 for details on the syntax of a MIME type.

The JRE data transfer implementation interprets the parameter "class" of a MIME type as a representation class. The representation class reflects the class of the object being transferred. In other words, the representation class is the type of object returned by {@link Transferable#getTransferData}. For example, the MIME type of {@link #imageFlavor} is {@code "image/x-java-image;class=java.awt.Image"}, the primary type is {@code image}, the subtype is {@code x-java-image}, and the representation class is {@code java.awt.Image}. When {@code getTransferData} is invoked with a {@code DataFlavor} of {@code imageFlavor}, an instance of {@code java.awt.Image} is returned. It's important to note that {@code DataFlavor} does no error checking against the representation class. It is up to consumers of {@code DataFlavor}, such as {@code Transferable}, to honor the representation class.
Note, if you do not specify a representation class when creating a {@code DataFlavor}, the default representation class is used. See appropriate documentation for {@code DataFlavor}'s constructors.

Also, {@code DataFlavor} instances with the "text" primary MIME type may have a "charset" parameter. Refer to RFC 2046 and {@link #selectBestTextFlavor} for details on "text" MIME types and the "charset" parameter.

Equality of {@code DataFlavors} is determined by the primary type, subtype, and representation class. Refer to {@link #equals(DataFlavor)} for details. When determining equality, any optional parameters are ignored. For example, the following produces two {@code DataFlavors} that are considered identical:

   DataFlavor flavor1 = new DataFlavor(Object.class, "X-test/test; class=<java.lang.Object>; foo=bar");
   DataFlavor flavor2 = new DataFlavor(Object.class, "X-test/test; class=<java.lang.Object>; x=y");
   // The following returns true.
   flavor1.equals(flavor2);
 

For more information on the using data transfer with Swing see the How to Use Drag and Drop and Data Transfer, section in Java Tutorial.

imageFlavor

public static final DataFlavor imageFlavor

The DataFlavor representing a Java Image class, where:

     representationClass = java.awt.Image
     mimeType            = "image/x-java-image"
 

javaFileListFlavor

public static final DataFlavor javaFileListFlavor

To transfer a list of files to/from Java (and the underlying platform) a DataFlavor of this type/subtype and representation class of java.util.List is used. Each element of the list is required/guaranteed to be of type java.io.File.

javaJVMLocalObjectMimeType

public static final String javaJVMLocalObjectMimeType

To transfer a reference to an arbitrary Java object reference that has no associated MIME Content-type, across a Transferable interface WITHIN THE SAME JVM, a DataFlavor with this type/subtype is used, with a representationClass equal to the type of the class/interface being passed across the Transferable.

The object reference returned from Transferable.getTransferData for a DataFlavor with this MIME Content-Type is required to be an instance of the representation Class of the DataFlavor.

javaRemoteObjectMimeType

public static final String javaRemoteObjectMimeType

In order to pass a live link to a Remote object via a Drag and Drop ACTION_LINK operation a Mime Content Type of application/x-java-remote-object should be used, where the representation class of the DataFlavor represents the type of the Remote interface to be transferred.

javaSerializedObjectMimeType

public static final String javaSerializedObjectMimeType

A MIME Content-Type of application/x-java-serialized-object represents a graph of Java object(s) that have been made persistent. The representation class associated with this DataFlavor identifies the Java type of an object returned as a reference from an invocation java.awt.datatransfer.getTransferData.

plainTextFlavor

public static final DataFlavor plainTextFlavor

The DataFlavor representing plain text with Unicode encoding, where:

     representationClass = InputStream
     mimeType            = "text/plain; charset=unicode"
 

This DataFlavor has been deprecated because (1) Its representation is an InputStream, an 8-bit based representation, while Unicode is a 16-bit character set; and (2) The charset "unicode" is not well-defined. "unicode" implies a particular platform's implementation of Unicode, not a cross-platform implementation.

stringFlavor

public static final DataFlavor stringFlavor

The DataFlavor representing a Java Unicode String class, where:

     representationClass = java.lang.String
     mimeType           = "application/x-java-serialized-object"        
 

DataFlavor

public DataFlavor()

Constructs a new DataFlavor. This constructor is provided only for the purpose of supporting the Externalizable interface. It is not intended for public (client) use.

DataFlavor

public DataFlavor(Class representationClass,
                  String humanPresentableName)

Constructs a DataFlavor that represents a Java class.

The returned DataFlavor will have the following characteristics:

    representationClass = representationClass
    mimeType            = application/x-java-serialized-object        
 

Parameters:

representationClass - the class used to transfer data in this flavor

humanPresentableName - the human-readable string used to identify this flavor; if this parameter is null then the value of the the MIME Content Type is used

DataFlavor

public DataFlavor(String mimeType)
           throws ClassNotFoundException

Constructs a DataFlavor from a mimeType string. The string can specify a "class=" parameter to create a DataFlavor with the desired representation class. If the string does not contain "class=" parameter, java.io.InputStream is used as default.

Parameters:

mimeType - the string used to identify the MIME type for this flavor; if the class specified by "class=" parameter is not successfully loaded, then an ClassNotFoundException is thrown

Throws:

ClassNotFoundException - if the class is not loaded

DataFlavor

public DataFlavor(String mimeType,
                  String humanPresentableName)

Constructs a DataFlavor that represents a MimeType.

The returned DataFlavor will have the following characteristics:

If the mimeType is "application/x-java-serialized-object; class=<representation class>", the result is the same as calling new DataFlavor(Class:forName(<representation class>).

Otherwise:

     representationClass = InputStream
     mimeType            = mimeType         
 

Parameters:

mimeType - the string used to identify the MIME type for this flavor; if the the mimeType does not specify a "class=" parameter, or if the class is not successfully loaded, then an IllegalArgumentException is thrown

humanPresentableName - the human-readable string used to identify this flavor; if this parameter is null then the value of the the MIME Content Type is used

DataFlavor

public DataFlavor(String mimeType,
                  String humanPresentableName,
                  ClassLoader classLoader)
           throws ClassNotFoundException

Constructs a DataFlavor that represents a MimeType.

The returned DataFlavor will have the following characteristics:

If the mimeType is "application/x-java-serialized-object; class=<representation class>", the result is the same as calling new DataFlavor(Class:forName(<representation class>).

Otherwise:

     representationClass = InputStream
     mimeType            = mimeType         
 

Parameters:

mimeType - the string used to identify the MIME type for this flavor

humanPresentableName - the human-readable string used to identify this flavor

classLoader - the class loader to use

Throws:

ClassNotFoundException - if the class is not loaded

clone

public Object clone()
             throws CloneNotSupportedException

Returns a clone of this DataFlavor.

Overrides:

clone in class Object

Returns:

a clone of this DataFlavor

Throws:

CloneNotSupportedException

equals

public boolean equals(DataFlavor that)

Tests a DataFlavor to this DataFlavor for equality. Two DataFlavors are considered equal if and only if their MIME primary type and subtype and representation class are equal. Additionally, if the primary type is "text", the subtype denotes a text flavor which supports the charset parameter, and the representation class is not java.io.Reader, java.lang.String, java.nio.CharBuffer, or [C, the charset parameter must also be equal. If a charset is not explicitly specified for one or both DataFlavors, the platform default encoding is assumed. See selectBestTextFlavor for a list of text flavors which support the charset parameter.

Parameters:

that - the DataFlavor to compare with this

Returns:

true if that is equivalent to this DataFlavor; false otherwise

equals

public boolean equals(Object o)

Tests an arbitrary Object to this DataFlavor for equality. Two DataFlavors are considered equal if and only if their MIME primary type and subtype and representation class are equal. Additionally, if the primary type is "text", the subtype denotes a text flavor which supports the charset parameter, and the representation class is not java.io.Reader, java.lang.String, java.nio.CharBuffer, or [C, the charset parameter must also be equal. If a charset is not explicitly specified for one or both DataFlavors, the platform default encoding is assumed. See selectBestTextFlavor for a list of text flavors which support the charset parameter.

Overrides:

equals in class Object

Parameters:

o - the Object to compare with this

Returns:

true if that is equivalent to this DataFlavor; false otherwise

equals

public boolean equals(String s)

Compares only the mimeType against the passed in String and representationClass is not considered in the comparison. If representationClass needs to be compared, then equals(new DataFlavor(s)) may be used.

Parameters:

s

Returns:

true if the String (MimeType) is equal

getDefaultRepresentationClass

public final Class getDefaultRepresentationClass()

getDefaultRepresentationClassAsString

public final String getDefaultRepresentationClassAsString()

getHumanPresentableName

public String getHumanPresentableName()

Returns the human presentable name for the data format that this DataFlavor represents. This name would be localized for different countries.

Returns:

the human presentable name for the data format that this DataFlavor represents

getMimeType

public String getMimeType()

Returns the MIME type string for this DataFlavor.

Returns:

the MIME type string for this flavor

getParameter

public String getParameter(String paramName)

Returns the human presentable name for this DataFlavor if paramName equals "humanPresentableName". Otherwise returns the MIME type value associated with paramName.

Parameters:

paramName - the parameter name requested

Returns:

the value of the name parameter, or null if there is no associated value

getPrimaryType

public String getPrimaryType()

Returns the primary MIME type for this DataFlavor.

Returns:

the primary MIME type of this DataFlavor

getReaderForText

public Reader getReaderForText(Transferable transferable)
                        throws UnsupportedFlavorException,
                               IOException

Gets a Reader for a text flavor, decoded, if necessary, for the expected charset (encoding). The supported representation classes are java.io.Reader, java.lang.String, java.nio.CharBuffer, [C, java.io.InputStream, java.nio.ByteBuffer, and [B.

Because text flavors which do not support the charset parameter are encoded in a non-standard format, this method should not be called for such flavors. However, in order to maintain backward-compatibility, if this method is called for such a flavor, this method will treat the flavor as though it supports the charset parameter and attempt to decode it accordingly. See selectBestTextFlavor for a list of text flavors which do not support the charset parameter.

Parameters:

transferable - the Transferable whose data will be requested in this flavor

Returns:

a Reader to read the Transferable's data

Throws:

UnsupportedFlavorException - if the Transferable does not support this flavor

IOException - if the data cannot be read because of an I/O error

getRepresentationClass

public Class getRepresentationClass()

Returns the Class which objects supporting this DataFlavor will return when this DataFlavor is requested.

Returns:

the Class which objects supporting this DataFlavor will return when this DataFlavor is requested

getSubType

public String getSubType()

Returns the sub MIME type of this DataFlavor.

Returns:

the Sub MIME type of this DataFlavor

getTextPlainUnicodeFlavor

public static final DataFlavor getTextPlainUnicodeFlavor()

Returns a DataFlavor representing plain text with Unicode encoding, where:

     representationClass = java.io.InputStream
     mimeType            = "text/plain;
                            charset=<platform default Unicode encoding>"
 

Sun's implementation for Microsoft Windows uses the encoding utf-16le. Sun's implementation for Solaris and Linux uses the encoding iso-10646-ucs-2.

Returns:

a DataFlavor representing plain text with Unicode encoding

hashCode

public int hashCode()

Returns hash code for this DataFlavor. For two equal DataFlavors, hash codes are equal. For the String that matches DataFlavor.equals(String), it is not guaranteed that DataFlavor's hash code is equal to the hash code of the String.

Overrides:

hashCode in class Object

Returns:

a hash code for this DataFlavor

isFlavorJavaFileListType

public boolean isFlavorJavaFileListType()

Returns true if the DataFlavor specified represents a list of file objects.

Returns:

true if the DataFlavor specified represents a List of File objects

isFlavorRemoteObjectType

public boolean isFlavorRemoteObjectType()

Returns true if the DataFlavor specified represents a remote object.

Returns:

true if the DataFlavor specified represents a Remote Object

isFlavorSerializedObjectType

public boolean isFlavorSerializedObjectType()

Returns true if the DataFlavor specified represents a serialized object.

Returns:

true if the DataFlavor specified represents a Serialized Object

isFlavorTextType

public boolean isFlavorTextType()

Returns whether this DataFlavor is a valid text flavor for this implementation of the Java platform. Only flavors equivalent to DataFlavor.stringFlavor and DataFlavors with a primary MIME type of "text" can be valid text flavors.

If this flavor supports the charset parameter, it must be equivalent to DataFlavor.stringFlavor, or its representation must be java.io.Reader, java.lang.String, java.nio.CharBuffer, [C, java.io.InputStream, java.nio.ByteBuffer, or [B. If the representation is java.io.InputStream, java.nio.ByteBuffer, or [B, then this flavor's charset parameter must be supported by this implementation of the Java platform. If a charset is not specified, then the platform default charset, which is always supported, is assumed.

If this flavor does not support the charset parameter, its representation must be java.io.InputStream, java.nio.ByteBuffer, or [B.

See selectBestTextFlavor for a list of text flavors which support the charset parameter.

Returns:

true if this DataFlavor is a valid text flavor as described above; false otherwise

isMimeTypeEqual

public final boolean isMimeTypeEqual(DataFlavor dataFlavor)

Compares the mimeType of two DataFlavor objects. No parameters are considered.

Parameters:

dataFlavor - the DataFlavor to be compared

Returns:

true if the MimeTypes are equal, otherwise false

isMimeTypeEqual

public boolean isMimeTypeEqual(String mimeType)

Returns whether the string representation of the MIME type passed in is equivalent to the MIME type of this DataFlavor. Parameters are not included in the comparison.

Parameters:

mimeType - the string representation of the MIME type

Returns:

true if the string representation of the MIME type passed in is equivalent to the MIME type of this DataFlavor; false otherwise

isMimeTypeSerializedObject

public boolean isMimeTypeSerializedObject()

Does the DataFlavor represent a serialized object?

isRepresentationClassByteBuffer

public boolean isRepresentationClassByteBuffer()

Returns whether the representation class for this DataFlavor is java.nio.ByteBuffer or a subclass thereof.

isRepresentationClassCharBuffer

public boolean isRepresentationClassCharBuffer()

Returns whether the representation class for this DataFlavor is java.nio.CharBuffer or a subclass thereof.

isRepresentationClassInputStream

public boolean isRepresentationClassInputStream()

Does the DataFlavor represent a java.io.InputStream?

isRepresentationClassReader

public boolean isRepresentationClassReader()

Returns whether the representation class for this DataFlavor is java.io.Reader or a subclass thereof.

isRepresentationClassRemote

public boolean isRepresentationClassRemote()

Returns true if the representation class is Remote.

Returns:

true if the representation class is Remote

isRepresentationClassSerializable

public boolean isRepresentationClassSerializable()

Returns true if the representation class can be serialized.

Returns:

true if the representation class can be serialized

match

public boolean match(DataFlavor that)

Tests a DataFlavor to this DataFlavor for equality. Two DataFlavors are considered equal if and only if their MIME primary type and subtype and representation class are equal. Additionally, if the primary type is "text", the subtype denotes a text flavor which supports the charset parameter, and the representation class is not java.io.Reader, java.lang.String, java.nio.CharBuffer, or [C, the charset parameter must also be equal. If a charset is not explicitly specified for one or both DataFlavors, the platform default encoding is assumed. See selectBestTextFlavor for a list of text flavors which support the charset parameter.

Parameters:

that - the DataFlavor to compare with this

Returns:

true if that is equivalent to this DataFlavor; false otherwise

normalizeMimeType

protected String normalizeMimeType(String mimeType)

Called for each MIME type string to give DataFlavor subtypes the opportunity to change how the normalization of MIME types is accomplished. One possible use would be to add default parameter/value pairs in cases where none are present in the MIME type string passed in. This method is never invoked by this implementation from 1.1 onwards.

Parameters:

mimeType

normalizeMimeTypeParameter

protected String normalizeMimeTypeParameter(String parameterName,
                                            String parameterValue)

Called on DataFlavor for every MIME Type parameter to allow DataFlavor subclasses to handle special parameters like the text/plain charset parameters, whose values are case insensitive. (MIME type parameter values are supposed to be case sensitive.

This method is called for each parameter name/value pair and should return the normalized representation of the parameterValue. This method is never invoked by this implementation from 1.1 onwards.

Parameters:

parameterName

parameterValue

readExternal

public synchronized void readExternal(ObjectInput is)
                               throws IOException,
                                      ClassNotFoundException

Restores this DataFlavor from a Serialized state.

Parameters:

is

Throws:

IOException

ClassNotFoundException

selectBestTextFlavor

public static final DataFlavor selectBestTextFlavor(DataFlavor[] availableFlavors)

Selects the best text DataFlavor from an array of DataFlavors. Only DataFlavor.stringFlavor, and equivalent flavors, and flavors that have a primary MIME type of "text", are considered for selection.

Flavors are first sorted by their MIME types in the following order:

• "text/sgml"
• "text/xml"
• "text/html"
• "text/rtf"
• "text/enriched"
• "text/richtext"
• "text/uri-list"
• "text/tab-separated-values"
• "text/t140"
• "text/rfc822-headers"
• "text/parityfec"
• "text/directory"
• "text/css"
• "text/calendar"
• "application/x-java-serialized-object"
• "text/plain"
• "text/<other>"

For example, "text/sgml" will be selected over "text/html", and DataFlavor.stringFlavor will be chosen over DataFlavor.plainTextFlavor.

If two or more flavors share the best MIME type in the array, then that MIME type will be checked to see if it supports the charset parameter.

The following MIME types support, or are treated as though they support, the charset parameter:

• "text/sgml"
• "text/xml"
• "text/html"
• "text/enriched"
• "text/richtext"
• "text/uri-list"
• "text/directory"
• "text/css"
• "text/calendar"
• "application/x-java-serialized-object"
• "text/plain"

The following MIME types do not support, or are treated as though they do not support, the charset parameter:

• "text/rtf"
• "text/tab-separated-values"
• "text/t140"
• "text/rfc822-headers"
• "text/parityfec"

For "text/<other>" MIME types, the first time the JRE needs to determine whether the MIME type supports the charset parameter, it will check whether the parameter is explicitly listed in an arbitrarily chosen DataFlavor which uses that MIME type. If so, the JRE will assume from that point on that the MIME type supports the charset parameter and will not check again. If the parameter is not explicitly listed, the JRE will assume from that point on that the MIME type does not support the charset parameter and will not check again. Because this check is performed on an arbitrarily chosen DataFlavor, developers must ensure that all DataFlavors with a "text/<other>" MIME type specify the charset parameter if it is supported by that MIME type. Developers should never rely on the JRE to substitute the platform's default charset for a "text/<other>" DataFlavor. Failure to adhere to this restriction will lead to undefined behavior.

If the best MIME type in the array does not support the charset parameter, the flavors which share that MIME type will then be sorted by their representation classes in the following order: java.io.InputStream, java.nio.ByteBuffer, [B, <all others>.

If two or more flavors share the best representation class, or if no flavor has one of the three specified representations, then one of those flavors will be chosen non-deterministically.

If the best MIME type in the array does support the charset parameter, the flavors which share that MIME type will then be sorted by their representation classes in the following order: java.io.Reader, java.lang.String, java.nio.CharBuffer, [C, <all others>.

If two or more flavors share the best representation class, and that representation is one of the four explicitly listed, then one of those flavors will be chosen non-deterministically. If, however, no flavor has one of the four specified representations, the flavors will then be sorted by their charsets. Unicode charsets, such as "UTF-16", "UTF-8", "UTF-16BE", "UTF-16LE", and their aliases, are considered best. After them, the platform default charset and its aliases are selected. "US-ASCII" and its aliases are worst. All other charsets are chosen in alphabetical order, but only charsets supported by this implementation of the Java platform will be considered.

If two or more flavors share the best charset, the flavors will then again be sorted by their representation classes in the following order: java.io.InputStream, java.nio.ByteBuffer, [B, <all others>.

If two or more flavors share the best representation class, or if no flavor has one of the three specified representations, then one of those flavors will be chosen non-deterministically.

Parameters:

availableFlavors - an array of available DataFlavors

Returns:

the best (highest fidelity) flavor according to the rules specified above, or null, if availableFlavors is null, has zero length, or contains no text flavors

setHumanPresentableName

public void setHumanPresentableName(String humanPresentableName)

Sets the human presentable name for the data format that this DataFlavor represents. This name would be localized for different countries.

Parameters:

humanPresentableName - the new human presentable name

toString

public String toString()

String representation of this DataFlavor and its parameters. The resulting String contains the name of the DataFlavor class, this flavor's MIME type, and its representation class. If this flavor has a primary MIME type of "text", supports the charset parameter, and has an encoded representation, the flavor's charset is also included. See selectBestTextFlavor for a list of text flavors which support the charset parameter.

Overrides:

toString in class Object

Returns:

string representation of this DataFlavor

tryToLoadClass

protected static final Class tryToLoadClass(String className,
                                            ClassLoader fallback)
                                     throws ClassNotFoundException

Tries to load a class from: the bootstrap loader, the system loader, the context loader (if one is present) and finally the loader specified.

Parameters:

className - the name of the class to be loaded

fallback - the fallback loader

Returns:

the class loaded

Throws:

ClassNotFoundException - if class is not found

writeExternal

public synchronized void writeExternal(ObjectOutput os)
                                throws IOException

Serializes this DataFlavor.

Parameters:

os

Throws:

IOException