dataflavor.java

JAVA基本类源代码,大家可以学习学习!

/*
 * @(#)DataFlavor.java	1.75 04/01/13
 *
 * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package java.awt.datatransfer;

import java.awt.Toolkit;
import java.io.*;
import java.nio.*;
import java.util.*;

import sun.awt.datatransfer.DataTransferer;

/**
 * Each instance represents the opaque concept of a data format as would
 * appear on a clipboard, during drag and drop, or in a file system.
 * <p>
 * <code>DataFlavor</code> objects are constant and never change once
 * instantiated.
 * </p>
 *
 * @version     1.75, 01/13/04
 * @author      Blake Sullivan
 * @author      Laurence P. G. Cable
 * @author      Jeff Dunn
 */
public class DataFlavor implements Externalizable, Cloneable {
    
    private static final long serialVersionUID = 8367026044764648243L;
    private static final Class ioInputStreamClass = java.io.InputStream.class;

    /**
     * Tries to load a class from: the bootstrap loader, the system loader,
     * the context loader (if one is present) and finally the loader specified.
     *
     * @param className the name of the class to be loaded
     * @param fallback the fallback loader
     * @return the class loaded
     * @exception ClassNotFoundException if class is not found
     */
    protected final static Class tryToLoadClass(String className,
						ClassLoader fallback) 
        throws ClassNotFoundException
    {
	ClassLoader systemClassLoader = (ClassLoader)
	    java.security.AccessController.doPrivileged(
                new java.security.PrivilegedAction() {
		    public Object run() {
			ClassLoader cl = Thread.currentThread().
			    getContextClassLoader();
			return (cl != null)
			    ? cl
			    : ClassLoader.getSystemClassLoader();
		    }
		    });
	
	try {
	    return Class.forName(className, true, systemClassLoader);
	} catch (ClassNotFoundException e2) {
	    if (fallback != null) {
		return Class.forName(className, true, fallback);
	    } else {
		throw new ClassNotFoundException(className);
	    }
	}
    }
    
    /*
     * private initializer
     */
    
    static private DataFlavor createConstant(Class rc, String prn) {
        try {
            return new DataFlavor(rc, prn);
        } catch (Exception e) {
            return null;
        }
    }
    
    /*
     * private initializer
     */
    
    static private DataFlavor createConstant(String mt, String prn) {
        try {
            return new DataFlavor(mt, prn);
        } catch (Exception e) {
            return null;
        }
    }
    
    /**
     * The <code>DataFlavor</code> representing a Java Unicode String class,
     * where:
     * <pre>
     *     representationClass = java.lang.String
     *     mimeType           = "application/x-java-serialized-object"        
     * </pre> 
     */
    
    public static final DataFlavor stringFlavor = createConstant(java.lang.String.class, "Unicode String");
    
    /**
     * The <code>DataFlavor</code> representing a Java Image class,
     * where:
     * <pre>
     *     representationClass = java.awt.Image
     *     mimeType            = "image/x-java-image"
     * </pre>
     */

    public static final DataFlavor imageFlavor = createConstant("image/x-java-image; class=java.awt.Image", "Image");
    
    /**
     * The <code>DataFlavor</code> representing plain text with Unicode
     * encoding, where:
     * <pre>
     *     representationClass = InputStream
     *     mimeType            = "text/plain; charset=unicode"
     * </pre>
     * This <code>DataFlavor</code> has been <b>deprecated</b> 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.
     *
     * @deprecated as of 1.3. Use <code>DataFlavor.getReaderForText(
     *             Transferable)</code> instead of <code>Transferable.
     *             getTransferData(DataFlavor.plainTextFlavor)</code>.
     */
    
    public static final DataFlavor plainTextFlavor = createConstant("text/plain; charset=unicode; class=java.io.InputStream", "Plain Text"); 
    
    
    /**
     * 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 <code>DataFlavor</code>
     * identifies the Java type of an object returned as a reference
     * from an invocation <code>java.awt.datatransfer.getTransferData</code>.
     *
     */
    
    public static final String javaSerializedObjectMimeType = "application/x-java-serialized-object";
    
    /**
     * To transfer a list of files to/from Java (and the underlying
     * platform) a <code>DataFlavor</code> of this type/subtype and
     * representation class of <code>java.util.List</code> is used.
     * Each element of the list is required/guaranteed to be of type
     * <code>java.io.File</code>.
     */
    
    public static final DataFlavor javaFileListFlavor = createConstant("application/x-java-file-list;class=java.util.List", null);

    /**
     * To transfer a reference to an arbitrary Java object reference that
     * has no associated MIME Content-type, across a <code>Transferable</code>
     * interface WITHIN THE SAME JVM, a <code>DataFlavor</code>
     * with this type/subtype is used, with a <code>representationClass</code>
     * equal to the type of the class/interface being passed across the
     * <code>Transferble</code>.
     * <p>
     * The object reference returned from 
     * <code>Transferable.getTransferData</code> for a <code>DataFlavor</code>
     * with this MIME Content-Type is required to be
     * an instance of the representation Class of the <code>DataFlavor</code>.
     */
 
    public static final String javaJVMLocalObjectMimeType = "application/x-java-jvm-local-objectref";
    
    /**
     * In order to pass a live link to a Remote object via a Drag and Drop
     * <code>ACTION_LINK</code> operation a Mime Content Type of
     * application/x-java-remote-object should be used,
     * where the representation class of the <code>DataFlavor</code> 
     * represents the type of the <code>Remote</code> interface to be
     * transferred.
     */

    public static final String javaRemoteObjectMimeType = "application/x-java-remote-object";

    /**
     * Constructs a new <code>DataFlavor</code>.  This constructor is
     * provided only for the purpose of supporting the
     * <code>Externalizable</code> interface.  It is not 
     * intended for public (client) use.
     *
     * @since 1.2
     */
    public DataFlavor() { 
        super(); 
    } 

    /**
     * Constructs a fully specified <code>DataFlavor</code>.
     *
     * @exception NullPointerException if either <code>primaryType</code>,
     *            <code>subType</code> or <code>representationClass</code> is null
     */
    private DataFlavor(String primaryType, String subType, MimeTypeParameterList params, Class representationClass, String humanPresentableName) {
        super();
        if (primaryType == null) {
            throw new NullPointerException("primaryType");
        }
        if (subType == null) {
            throw new NullPointerException("subType");
        }
        if (representationClass == null) {
            throw new NullPointerException("representationClass");
        }
        
        if (params == null) params = new MimeTypeParameterList();
        
        params.set("class", representationClass.getName());
        
        if (humanPresentableName == null) {
            humanPresentableName = (String)params.get("humanPresentableName");
            
            if (humanPresentableName == null)
                humanPresentableName = primaryType + "/" + subType;
        }
        
        try {
            mimeType = new MimeType(primaryType, subType, params);
        } catch (MimeTypeParseException mtpe) {
            throw new IllegalArgumentException("MimeType Parse Exception: " + mtpe.getMessage());
        }
        
        this.representationClass  = representationClass;
        this.humanPresentableName = humanPresentableName;
        
        mimeType.removeParameter("humanPresentableName");
    }
    
    /**
     * Constructs a <code>DataFlavor</code> that represents a Java class.
     * <p>
     * The returned <code>DataFlavor</code> will have the following
     * characteristics:
     * <pre>
     *    representationClass = representationClass
     *    mimeType            = application/x-java-serialized-object        
     * </pre>
     * @param representationClass the class used to transfer data in this flavor
     * @param humanPresentableName the human-readable string used to identify 
     *                 this flavor; if this parameter is <code>null</code>
     *		       then the value of the the MIME Content Type is used
     * @exception NullPointerException if <code>representationClass</code> is null
     */
    public DataFlavor(Class representationClass, String humanPresentableName) {
        this("application", "x-java-serialized-object", null, representationClass, humanPresentableName);
        if (representationClass == null) {
            throw new NullPointerException("representationClass");
        }
    }

    /**
     * Constructs a <code>DataFlavor</code> that represents a
     * <code>MimeType</code>.
     * <p>
     * The returned <code>DataFlavor</code> will have the following
     * characteristics:
     * <p>
     * If the <code>mimeType</code> is
     * "application/x-java-serialized-object; class=&lt;representation class&gt;",
     * the result is the same as calling
     * <code>new DataFlavor(Class:forName(&lt;representation class&gt;)</code>.
     * <p>
     * Otherwise:
     * <pre>
     *     representationClass = InputStream
     *     mimeType            = mimeType         
     * </pre>
     * @param mimeType the string used to identify the MIME type for this flavor;
     *                 if the the <code>mimeType</code> does not specify a
     *                 "class=" parameter, or if the class is not successfully
     *                 loaded, then an <code>IllegalArgumentException</code>
     *		       is thrown
     * @param humanPresentableName the human-readable string used to identify 
     *                 this flavor; if this parameter is <code>null</code>
     *		       then the value of the the MIME Content Type is used
     * @exception IllegalArgumentException if <code>mimeType</code> is
     *	               invalid or if the class is not successfully loaded
     * @exception NullPointerException if <code>mimeType</code> is null
     */
    public DataFlavor(String mimeType, String humanPresentableName) {
        super();
        if (mimeType == null) {
            throw new NullPointerException("mimeType");
        }
        try {
            initialize(mimeType, humanPresentableName, this.getClass().getClassLoader());
        } catch (MimeTypeParseException mtpe) {
            throw new IllegalArgumentException("failed to parse:" + mimeType);
        } catch (ClassNotFoundException cnfe) {
            throw new IllegalArgumentException("can't find specified class: " + cnfe.getMessage());
        }
    }
    
    /**
     * Constructs a <code>DataFlavor</code> that represents a
     * <code>MimeType</code>.
     * <p>
     * The returned <code>DataFlavor</code> will have the following
     * characteristics:
     * <p>
     * If the mimeType is
     * "application/x-java-serialized-object; class=&lt;representation class&gt;",
     * the result is the same as calling
     * <code>new DataFlavor(Class:forName(&lt;representation class&gt;)</code>.
     * <p>
     * Otherwise:
     * <pre>
     *     representationClass = InputStream
     *     mimeType            = mimeType         
     * </pre>
     * @param mimeType the string used to identify the MIME type for this flavor
     * @param humanPresentableName the human-readable string used to 
     *		identify this flavor
     * @param classLoader the class loader to use
     * @exception ClassNotFoundException if the class is not loaded
     * @exception IllegalArgumentException if <code>mimeType</code> is
     *	               invalid
     * @exception NullPointerException if <code>mimeType</code> is null
     */
    public DataFlavor(String mimeType, String humanPresentableName, ClassLoader classLoader) throws ClassNotFoundException {
	super();
        if (mimeType == null) {