Java example source code file (TransferableProxy.java)

This example Java source code file (TransferableProxy.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

awt, bytearrayoutputstream, class, classloader, classloaderobjectinputstream, classloaderobjectoutputstream, classnotfoundexception, datatransfer, hashmap, hashset, ioexception, map, privilegedaction, reflection, security, set, transferable, transferableproxy, util

The TransferableProxy.java Java example source code

/*
 * Copyright (c) 2000, 2013, 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
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package sun.awt.datatransfer;

import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.Transferable;
import java.awt.datatransfer.UnsupportedFlavorException;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.ObjectStreamClass;
import java.io.OutputStream;
import java.lang.reflect.Modifier;
import java.lang.reflect.Proxy;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;


/**
 * Proxies for another Transferable so that Serializable objects are never
 * returned directly by DnD or the Clipboard. Instead, a new instance of the
 * object is returned.
 *
 * @author Lawrence P.G. Cable
 * @author David Mendenhall
 *
 * @since 1.4
 */
public class TransferableProxy implements Transferable {
    public TransferableProxy(Transferable t, boolean local) {
        transferable = t;
        isLocal = local;
    }
    public DataFlavor[] getTransferDataFlavors() {
        return transferable.getTransferDataFlavors();
    }
    public boolean isDataFlavorSupported(DataFlavor flavor) {
        return transferable.isDataFlavorSupported(flavor);
    }
    public Object getTransferData(DataFlavor df)
        throws UnsupportedFlavorException, IOException
    {
        Object data = transferable.getTransferData(df);

        // If the data is a Serializable object, then create a new instance
        // before returning it. This insulates applications sharing DnD and
        // Clipboard data from each other.
        if (data != null && isLocal && df.isFlavorSerializedObjectType()) {
            ByteArrayOutputStream baos = new ByteArrayOutputStream();

            ClassLoaderObjectOutputStream oos =
                new ClassLoaderObjectOutputStream(baos);
            oos.writeObject(data);

            ByteArrayInputStream bais =
                new ByteArrayInputStream(baos.toByteArray());

            try {
                ClassLoaderObjectInputStream ois =
                    new ClassLoaderObjectInputStream(bais,
                                                     oos.getClassLoaderMap());
                data = ois.readObject();
            } catch (ClassNotFoundException cnfe) {
                throw (IOException)new IOException().initCause(cnfe);
            }
        }

        return data;
    }

    protected final Transferable transferable;
    protected final boolean isLocal;
}

final class ClassLoaderObjectOutputStream extends ObjectOutputStream {
    private final Map<Set map =
        new HashMap<Set();

    ClassLoaderObjectOutputStream(OutputStream os) throws IOException {
        super(os);
    }

    protected void annotateClass(final Class<?> cl) throws IOException {
        ClassLoader classLoader =
            (ClassLoader)AccessController.doPrivileged(new PrivilegedAction() {
                public Object run() {
                    return cl.getClassLoader();
                }
            });

        Set<String> s = new HashSet(1);
        s.add(cl.getName());

        map.put(s, classLoader);
    }
    protected void annotateProxyClass(final Class<?> cl) throws IOException {
        ClassLoader classLoader =
            (ClassLoader)AccessController.doPrivileged(new PrivilegedAction() {
                public Object run() {
                    return cl.getClassLoader();
                }
            });

        Class[] interfaces = cl.getInterfaces();
        Set<String> s = new HashSet(interfaces.length);
        for (int i = 0; i < interfaces.length; i++) {
            s.add(interfaces[i].getName());
        }

        map.put(s, classLoader);
    }

    Map<Set getClassLoaderMap() {
        return new HashMap(map);
    }
}

final class ClassLoaderObjectInputStream extends ObjectInputStream {
    private final Map<Set map;

    ClassLoaderObjectInputStream(InputStream is,
                                 Map<Set map)
      throws IOException {
        super(is);
        if (map == null) {
            throw new NullPointerException("Null map");
        }
        this.map = map;
    }

    protected Class<?> resolveClass(ObjectStreamClass classDesc)
      throws IOException, ClassNotFoundException {
        String className = classDesc.getName();

        Set<String> s = new HashSet(1);
        s.add(className);

        ClassLoader classLoader = map.get(s);
        if (classLoader != null) {
            return Class.forName(className, false, classLoader);
        } else {
            return super.resolveClass(classDesc);
        }
    }

    protected Class<?> resolveProxyClass(String[] interfaces)
      throws IOException, ClassNotFoundException {

        Set<String> s = new HashSet(interfaces.length);
        for (int i = 0; i < interfaces.length; i++) {
            s.add(interfaces[i]);
        }

        ClassLoader classLoader = map.get(s);
        if (classLoader == null) {
            return super.resolveProxyClass(interfaces);
        }

        // The code below is mostly copied from the superclass.
        ClassLoader nonPublicLoader = null;
        boolean hasNonPublicInterface = false;

        // define proxy in class loader of non-public interface(s), if any
        Class[] classObjs = new Class[interfaces.length];
        for (int i = 0; i < interfaces.length; i++) {
            Class cl = Class.forName(interfaces[i], false, classLoader);
            if ((cl.getModifiers() & Modifier.PUBLIC) == 0) {
                if (hasNonPublicInterface) {
                    if (nonPublicLoader != cl.getClassLoader()) {
                        throw new IllegalAccessError(
                            "conflicting non-public interface class loaders");
                    }
                } else {
                    nonPublicLoader = cl.getClassLoader();
                    hasNonPublicInterface = true;
                }
            }
            classObjs[i] = cl;
        }
        try {
            return Proxy.getProxyClass(hasNonPublicInterface ?
                                       nonPublicLoader : classLoader,
                                       classObjs);
        } catch (IllegalArgumentException e) {
            throw new ClassNotFoundException(null, e);
        }
    }
}