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 * Copyright (c) 1997, 2006, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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package javax.activation;

import java.io.InputStream;

import java.io.IOException;

import java.io.OutputStream;

import java.io.PipedInputStream;

import java.io.PipedOutputStream;

import java.io.OutputStreamWriter;

import java.net.URL;

import java.awt.datatransfer.Transferable;

import java.awt.datatransfer.DataFlavor;

import java.awt.datatransfer.UnsupportedFlavorException;

/**

 * 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. <p>

 *

 * <b>DataHandler and the Transferable Interface</b><p>

 * 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.<p>

 *

 * <b>DataHandler and CommandMaps</b><p>

 * The DataHandler keeps track of the current CommandMap that it uses to

 * service requests for commands (<code>getCommand</code>,

 * <code>getAllCommands</code>, <code>getPreferredCommands</code>).

 * Each instance of a DataHandler may have a CommandMap associated with

 * it using the <code>setCommandMap</code> method.  If a CommandMap was

 * not set, DataHandler calls the <code>getDefaultCommandMap</code>

 * method in CommandMap and uses the value it returns. See

 * <i>CommandMap</i> for more information. <p>

 *

 * <b>DataHandler and URLs</b><p>

 * The current DataHandler implementation creates a private

 * instance of URLDataSource when it is constructed with a URL.

 *

 * @see javax.activation.CommandMap

 * @see javax.activation.DataContentHandler

 * @see javax.activation.DataSource

 * @see javax.activation.URLDataSource

 *

 * @since 1.6

 */

public class DataHandler implements Transferable {

    // Use the datasource to indicate whether we were started via the

    // DataSource constructor or the object constructor.

    private DataSource dataSource = null;

    private DataSource objDataSource = null;

    // The Object and mimetype from the constructor (if passed in).

    // object remains null if it was instantiated with a

    // DataSource.

    private Object object = null;

    private String objectMimeType = null;

    // Keep track of the CommandMap

    private CommandMap currentCommandMap = null;

    // our transfer flavors

    private static final DataFlavor emptyFlavors[] = new DataFlavor[0];

    private DataFlavor transferFlavors[] = emptyFlavors;

    // our DataContentHandler

    private DataContentHandler dataContentHandler = null;

    private DataContentHandler factoryDCH = null;

    // our DataContentHandlerFactory

    private static DataContentHandlerFactory factory = null;

    private DataContentHandlerFactory oldFactory = null;

    // the short representation of the ContentType (sans params)

    private String shortType = null;

    /**

     * Create a <code>DataHandler</code> instance referencing the

     * specified DataSource.  The data exists in a byte stream form.

     * The DataSource will provide an InputStream to access the data.

     *

     * @param ds        the DataSource

     */

    public DataHandler(DataSource ds) {

        // save a reference to the incoming DS

        dataSource = ds;

        oldFactory = factory; // keep track of the factory

    }

    /**

     * Create a <code>DataHandler</code> 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.

     *

     * @param obj       the Java Object

     * @param mimeType  the MIME type of the object

     */

    public DataHandler(Object obj, String mimeType) {

        object = obj;

        objectMimeType = mimeType;

        oldFactory = factory; // keep track of the factory

    }

    /**

     * Create a <code>DataHandler</code> instance referencing a URL.

     * The DataHandler internally creates a <code>URLDataSource</code>

     * instance to represent the URL.

     *

     * @param url       a URL object

     */

    public DataHandler(URL url) {

        dataSource = new URLDataSource(url);

        oldFactory = factory; // keep track of the factory

    }

    /**

     * Return the CommandMap for this instance of DataHandler.

     */

    private synchronized CommandMap getCommandMap() {

        if (currentCommandMap != null)

            return currentCommandMap;

        else

            return CommandMap.getDefaultCommandMap();

    }

    /**

     * Return the DataSource associated with this instance

     * of DataHandler.

     * <p>

     * 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 <b>not</b>

     * instantiated with a DataSource are cached for performance

     * reasons.

     *

     * @return  a valid DataSource object for this DataHandler

     */

    public DataSource getDataSource() {

        if (dataSource == null) {

            // create one on the fly

            if (objDataSource == null)

                objDataSource = new DataHandlerDataSource(this);

            return objDataSource;

        }

        return dataSource;

    }

    /**

     * Return the name of the data object. If this DataHandler

     * was created with a DataSource, this method calls through

     * to the <code>DataSource.getName</code> method, otherwise it

     * returns <i>null</i>.

     *

     * @return  the name of the object

     */

    public String getName() {

        if (dataSource != null)

            return dataSource.getName();

        else

            return null;

    }

    /**

     * Return the MIME type of this object as retrieved from

     * the source object. Note that this is the <i>full</i>

     * type with parameters.

     *

     * @return  the MIME type

     */

    public String getContentType() {

        if (dataSource != null) // data source case

            return dataSource.getContentType();

        else

            return objectMimeType; // obj/type case

    }

    /**

     * Get the InputStream for this object. <p>

     *

     * For DataHandlers instantiated with a DataSource, the DataHandler

     * calls the <code>DataSource.getInputStream</code> method and

     * returns the result to the caller.

     * <p>

     * 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 <code>writeTo</code> 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.<p>

     *

     * @return  the InputStream representing this data

     * @exception IOException   if an I/O error occurs

     *

     * @see javax.activation.DataContentHandler#writeTo

     * @see javax.activation.UnsupportedDataTypeException

     */

    public InputStream getInputStream() throws IOException {

        InputStream ins = null;

        if (dataSource != null) {

            ins = dataSource.getInputStream();

        } else {

            DataContentHandler dch = getDataContentHandler();

            // we won't even try if we can't get a dch

            if (dch == null)

                throw new UnsupportedDataTypeException(

                                "no DCH for MIME type " + getBaseType());

            if (dch instanceof ObjectDataContentHandler) {

                if (((ObjectDataContentHandler)dch).getDCH() == null)

                    throw new UnsupportedDataTypeException(

                                "no object DCH for MIME type " + getBaseType());

            }

            // there is none but the default^^^^^^^^^^^^^^^^

            final DataContentHandler fdch = dch;

            // from bill s.

            // ce n'est pas une pipe!

            //

            // NOTE: This block of code needs to throw exceptions, but

            // can't because it is in another thread!!! ARG!

            //

            final PipedOutputStream pos = new PipedOutputStream();

            PipedInputStream pin = new PipedInputStream(pos);

            new Thread(

                       new Runnable() {

                public void run() {

                    try {

                        fdch.writeTo(object, objectMimeType, pos);

                    } catch (IOException e) {

                    } finally {

                        try {

                            pos.close();

                        } catch (IOException ie) { }

                    }

                }

            },

                      "DataHandler.getInputStream").start();

            ins = pin;

        }

        return ins;

    }

    /**

     * Write the data to an <code>OutputStream</code>.<p>

     *

     * If the DataHandler was created with a DataSource, writeTo

     * retrieves the InputStream and copies the bytes from the

     * InputStream to the OutputStream passed in.

     * <p>

     * 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

     * <code>writeTo</code> method on the <code>DataContentHandler</code>.

     *

     * @param os        the OutputStream to write to

     * @exception IOException   if an I/O error occurs

     */

    public void writeTo(OutputStream os) throws IOException {

        // for the DataSource case

        if (dataSource != null) {

            InputStream is = null;

            byte data[] = new byte[8*1024];

            int bytes_read;

            is = dataSource.getInputStream();

            try {

                while ((bytes_read = is.read(data)) > 0) {

                    os.write(data, 0, bytes_read);

                }

            } finally {

                is.close();

                is = null;

            }

        } else { // for the Object case

            DataContentHandler dch = getDataContentHandler();

            dch.writeTo(object, objectMimeType, os);

        }

    }

    /**

     * Get an OutputStream for this DataHandler to allow overwriting

     * the underlying data.

     * If the DataHandler was created with a DataSource, the

     * DataSource's <code>getOutputStream</code> method is called.

     * Otherwise, <code>null</code> is returned.

     *

     * @return the OutputStream

     *

     * @see javax.activation.DataSource#getOutputStream

     * @see javax.activation.URLDataSource

     */

    public OutputStream getOutputStream() throws IOException {

        if (dataSource != null)

            return dataSource.getOutputStream();

        else

            return null;

    }

    /**

     * Return the DataFlavors in which this data is available. <p>

     *

     * 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.<p>

     *

     * 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

     * <code>getTransferDataFlavors</code> method. <p>

     *

     * If a DataContentHandler can <i>not</i> 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 <code>java.io.InputStream</code> 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.

     *

     * @return  an array of data flavors in which this data can be transferred

     * @see javax.activation.DataContentHandler#getTransferDataFlavors

     */

    public synchronized DataFlavor[] getTransferDataFlavors() {

        if (factory != oldFactory) // if the factory has changed, clear cache

            transferFlavors = emptyFlavors;

        // if it's not set, set it...

        if (transferFlavors == emptyFlavors)

            transferFlavors = getDataContentHandler().getTransferDataFlavors();

        return transferFlavors;

    }

    /**

     * Returns whether the specified data flavor is supported

     * for this object.<p>

     *

     * This method iterates through the DataFlavors returned from

     * <code>getTransferDataFlavors</code>, comparing each with

     * the specified flavor.

     *

     * @param flavor    the requested flavor for the data

     * @return          true if the data flavor is supported

     * @see javax.activation.DataHandler#getTransferDataFlavors

     */

    public boolean isDataFlavorSupported(DataFlavor flavor) {

        DataFlavor[] lFlavors = getTransferDataFlavors();

        for (int i = 0; i < lFlavors.length; i++) {

            if (lFlavors[i].equals(flavor))

                return true;

        }

        return false;

    }

    /**

     * Returns an object that represents the data to be

     * transferred. The class of the object returned is defined by the

     * representation class of the data flavor.<p>

     *

     * <b>For DataHandler's created with DataSources or URLs:</b><p>

     *

     * 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 <code>getTransferData</code>

     * method. If the DataHandler fails to locate a DataContentHandler

     * and the flavor specifies this object's MIME type and the

     * <code>java.io.InputStream</code> class, this object's InputStream

     * is returned.

     * Otherwise it throws an UnsupportedFlavorException. <p>

     *

     * <b>For DataHandler's created with Objects:</b><p>

     *

     * 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.

     *

     * @param flavor    the requested flavor for the data

     * @return          the object

     * @exception UnsupportedFlavorException    if the data could not be

     *                  converted to the requested flavor

     * @exception IOException   if an I/O error occurs

     * @see javax.activation.ActivationDataFlavor

     */

    public Object getTransferData(DataFlavor flavor)

                                throws UnsupportedFlavorException, IOException {

        return getDataContentHandler().getTransferData(flavor, dataSource);

    }

    /**

     * Set the CommandMap for use by this DataHandler.

     * Setting it to <code>null</code> causes the CommandMap to revert

     * to the CommandMap returned by the

     * <code>CommandMap.getDefaultCommandMap</code> method.

     * Changing the CommandMap, or setting it to <code>null</code>,

     * clears out any data cached from the previous CommandMap.

     *

     * @param commandMap        the CommandMap to use in this DataHandler

     *

     * @see javax.activation.CommandMap#setDefaultCommandMap

     */

    public synchronized void setCommandMap(CommandMap commandMap) {

        if (commandMap != currentCommandMap || commandMap == null) {

            // clear cached values...

            transferFlavors = emptyFlavors;

            dataContentHandler = null;

            currentCommandMap = commandMap;

        }

    }

    /**

     * Return the <i>preferred</i> commands for this type of data.

     * This method calls the <code>getPreferredCommands</code> 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.

     *

     * @return  the CommandInfo objects representing the preferred commands

     *

     * @see javax.activation.CommandMap#getPreferredCommands

     */

    public CommandInfo[] getPreferredCommands() {

        if (dataSource != null)

            return getCommandMap().getPreferredCommands(getBaseType(),

                                                        dataSource);

        else

            return getCommandMap().getPreferredCommands(getBaseType());

    }

    /**

     * Return all the commands for this type of data.

     * This method returns an array containing all commands

     * for the type of data represented by this DataHandler. The

     * MIME type for the underlying data represented by this DataHandler

     * is used to call through to the <code>getAllCommands</code> method

     * of the CommandMap associated with this DataHandler.

     *

     * @return  the CommandInfo objects representing all the commands

     *

     * @see javax.activation.CommandMap#getAllCommands

     */

    public CommandInfo[] getAllCommands() {

        if (dataSource != null)

            return getCommandMap().getAllCommands(getBaseType(), dataSource);

        else

            return getCommandMap().getAllCommands(getBaseType());

    }

    /**

     * Get the command <i>cmdName</i>. Use the search semantics as

     * defined by the CommandMap installed in this DataHandler. The

     * MIME type for the underlying data represented by this DataHandler

     * is used to call through to the <code>getCommand</code> method

     * of the CommandMap associated with this DataHandler.

     *

     * @param cmdName   the command name

     * @return  the CommandInfo corresponding to the command

     *

     * @see javax.activation.CommandMap#getCommand

     */

    public CommandInfo getCommand(String cmdName) {

        if (dataSource != null)

            return getCommandMap().getCommand(getBaseType(), cmdName,

                                                                dataSource);

        else

            return getCommandMap().getCommand(getBaseType(), cmdName);

    }

    /**

     * Return the data in its preferred Object form. <p>

     *

     * If the DataHandler was instantiated with an object, return

     * the object. <p>

     *

     * 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

     * <code>DataContentHandler</code> can be found for the

     * the type of this data, the DataHandler returns an

     * InputStream for the data.

     *