/*

 * Copyright (c) 1996, 2014, 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 java.rmi.server;

import java.rmi.Remote;

import java.rmi.NoSuchObjectException;

import java.lang.reflect.Proxy;

import sun.rmi.server.Util;

/**

 * The <code>RemoteObject</code> class implements the

 * <code>java.lang.Object</code> behavior for remote objects.

 * <code>RemoteObject</code> provides the remote semantics of Object by

 * implementing methods for hashCode, equals, and toString.

 *

 * @author      Ann Wollrath

 * @author      Laird Dornin

 * @author      Peter Jones

 * @since       1.1

 */

public abstract class RemoteObject implements Remote, java.io.Serializable {

    /** The object's remote reference. */

    transient protected RemoteRef ref;

    /** indicate compatibility with JDK 1.1.x version of class */

    private static final long serialVersionUID = -3215090123894869218L;

    /**

     * Creates a remote object.

     */

    protected RemoteObject() {

        ref = null;

    }

    /**

     * Creates a remote object, initialized with the specified remote

     * reference.

     * @param newref remote reference

     */

    protected RemoteObject(RemoteRef newref) {

        ref = newref;

    }

    /**

     * Returns the remote reference for the remote object.

     *

     * <p>Note: The object returned from this method may be an instance of

     * an implementation-specific class.  The <code>RemoteObject</code>

     * class ensures serialization portability of its instances' remote

     * references through the behavior of its custom

     * <code>writeObject</code> and <code>readObject</code> methods.  An

     * instance of <code>RemoteRef</code> should not be serialized outside

     * of its <code>RemoteObject</code> wrapper instance or the result may

     * be unportable.

     *

     * @return remote reference for the remote object

     * @since 1.2

     */

    public RemoteRef getRef() {

        return ref;

    }

    /**

     * Returns the stub for the remote object <code>obj</code> passed

     * as a parameter. This operation is only valid <i>after</i>

     * the object has been exported.

     * @param obj the remote object whose stub is needed

     * @return the stub for the remote object, <code>obj</code>.

     * @exception NoSuchObjectException if the stub for the

     * remote object could not be found.

     * @since 1.2

     */

    @SuppressWarnings("deprecation")

    public static Remote toStub(Remote obj) throws NoSuchObjectException {

        if (obj instanceof RemoteStub ||

            (obj != null &&

             Proxy.isProxyClass(obj.getClass()) &&

             Proxy.getInvocationHandler(obj) instanceof

             RemoteObjectInvocationHandler))

        {

            return obj;

        } else {

            return sun.rmi.transport.ObjectTable.getStub(obj);

        }

    }

    /**

     * Returns a hashcode for a remote object.  Two remote object stubs

     * that refer to the same remote object will have the same hash code

     * (in order to support remote objects as keys in hash tables).

     *

     * @see             java.util.Hashtable

     */

    public int hashCode() {

        return (ref == null) ? super.hashCode() : ref.remoteHashCode();

    }

    /**

     * Compares two remote objects for equality.

     * Returns a boolean that indicates whether this remote object is

     * equivalent to the specified Object. This method is used when a

     * remote object is stored in a hashtable.

     * If the specified Object is not itself an instance of RemoteObject,

     * then this method delegates by returning the result of invoking the

     * <code>equals</code> method of its parameter with this remote object

     * as the argument.

     * @param   obj     the Object to compare with

     * @return  true if these Objects are equal; false otherwise.

     * @see             java.util.Hashtable

     */

    public boolean equals(Object obj) {

        if (obj instanceof RemoteObject) {

            if (ref == null) {

                return obj == this;

            } else {

                return ref.remoteEquals(((RemoteObject)obj).ref);

            }

        } else if (obj != null) {

            /*

             * Fix for 4099660: if object is not an instance of RemoteObject,

             * use the result of its equals method, to support symmetry is a

             * remote object implementation class that does not extend

             * RemoteObject wishes to support equality with its stub objects.

             */

            return obj.equals(this);

        } else {

            return false;

        }

    }

    /**

     * Returns a String that represents the value of this remote object.

     */

    public String toString() {

        String classname = Util.getUnqualifiedName(getClass());

        return (ref == null) ? classname :

            classname + "[" + ref.remoteToString() + "]";

    }

    /**

     * <code>writeObject</code> for custom serialization.

     *

     * <p>This method writes this object's serialized form for this class

     * as follows:

     *

     * <p>The {@link RemoteRef#getRefClass(java.io.ObjectOutput) getRefClass}

     * method is invoked on this object's <code>ref</code> field

     * to obtain its external ref type name.

     * If the value returned by <code>getRefClass</code> was

     * a non-<code>null</code> string of length greater than zero,

     * the <code>writeUTF</code> method is invoked on <code>out</code>

     * with the value returned by <code>getRefClass</code>, and then

     * the <code>writeExternal</code> method is invoked on

     * this object's <code>ref</code> field passing <code>out</code>

     * as the argument; otherwise,

     * the <code>writeUTF</code> method is invoked on <code>out</code>

     * with a zero-length string (<code>""</code>), and then

     * the <code>writeObject</code> method is invoked on <code>out</code>

     * passing this object's <code>ref</code> field as the argument.

     *

     * @serialData

     *

     * The serialized data for this class comprises a string (written with

     * <code>ObjectOutput.writeUTF</code>) that is either the external

     * ref type name of the contained <code>RemoteRef</code> instance

     * (the <code>ref</code> field) or a zero-length string, followed by

     * either the external form of the <code>ref</code> field as written by

     * its <code>writeExternal</code> method if the string was of non-zero

     * length, or the serialized form of the <code>ref</code> field as

     * written by passing it to the serialization stream's

     * <code>writeObject</code> if the string was of zero length.

     *

     * <p>If this object is an instance of

     * {@link RemoteStub} or {@link RemoteObjectInvocationHandler}

     * that was returned from any of

     * the <code>UnicastRemoteObject.exportObject</code> methods

     * and custom socket factories are not used,

     * the external ref type name is <code>"UnicastRef"</code>.

     *

     * If this object is an instance of

     * <code>RemoteStub</code> or <code>RemoteObjectInvocationHandler</code>

     * that was returned from any of

     * the <code>UnicastRemoteObject.exportObject</code> methods

     * and custom socket factories are used,

     * the external ref type name is <code>"UnicastRef2"</code>.

     *

     * If this object is an instance of

     * <code>RemoteStub</code> or <code>RemoteObjectInvocationHandler</code>

     * that was returned from any of

     * the <code>java.rmi.activation.Activatable.exportObject</code> methods,

     * the external ref type name is <code>"ActivatableRef"</code>.

     *

     * If this object is an instance of

     * <code>RemoteStub</code> or <code>RemoteObjectInvocationHandler</code>

     * that was returned from

     * the <code>RemoteObject.toStub</code> method (and the argument passed

     * to <code>toStub</code> was not itself a <code>RemoteStub</code>),

     * the external ref type name is a function of how the remote object

     * passed to <code>toStub</code> was exported, as described above.

     *

     * If this object is an instance of

     * <code>RemoteStub</code> or <code>RemoteObjectInvocationHandler</code>

     * that was originally created via deserialization,

     * the external ref type name is the same as that which was read

     * when this object was deserialized.

     *

     * <p>If this object is an instance of

     * <code>java.rmi.server.UnicastRemoteObject</code> that does not

     * use custom socket factories,

     * the external ref type name is <code>"UnicastServerRef"</code>.

     *

     * If this object is an instance of

     * <code>UnicastRemoteObject</code> that does

     * use custom socket factories,

     * the external ref type name is <code>"UnicastServerRef2"</code>.

     *

     * <p>Following is the data that must be written by the

     * <code>writeExternal</code> method and read by the

     * <code>readExternal</code> method of <code>RemoteRef</code>

     * implementation classes that correspond to the each of the

     * defined external ref type names:

     *

     * <p>For <code>"UnicastRef"</code>:

     *

     * <ul>

     *

     * <li>the hostname of the referenced remote object,

     * written by {@link java.io.ObjectOutput#writeUTF(String)}

     *

     * <li>the port of the referenced remote object,

     * written by {@link java.io.ObjectOutput#writeInt(int)}

     *

     * <li>the data written as a result of calling

     * {link java.rmi.server.ObjID#write(java.io.ObjectOutput)}

     * on the <code>ObjID</code> instance contained in the reference

     *

     * <li>the boolean value <code>false</code>,

     * written by {@link java.io.ObjectOutput#writeBoolean(boolean)}

     *

     * </ul>

     *

     * <p>For <code>"UnicastRef2"</code> with a

     * <code>null</code> client socket factory:

     *

     * <ul>

     *

     * <li>the byte value <code>0x00</code>

     * (indicating <code>null</code> client socket factory),

     * written by {@link java.io.ObjectOutput#writeByte(int)}

     *

     * <li>the hostname of the referenced remote object,

     * written by {@link java.io.ObjectOutput#writeUTF(String)}

     *

     * <li>the port of the referenced remote object,

     * written by {@link java.io.ObjectOutput#writeInt(int)}

     *

     * <li>the data written as a result of calling

     * {link java.rmi.server.ObjID#write(java.io.ObjectOutput)}

     * on the <code>ObjID</code> instance contained in the reference

     *

     * <li>the boolean value <code>false</code>,

     * written by {@link java.io.ObjectOutput#writeBoolean(boolean)}

     *

     * </ul>

     *

     * <p>For <code>"UnicastRef2"</code> with a

     * non-<code>null</code> client socket factory:

     *

     * <ul>

     *

     * <li>the byte value <code>0x01</code>

     * (indicating non-<code>null</code> client socket factory),

     * written by {@link java.io.ObjectOutput#writeByte(int)}

     *

     * <li>the hostname of the referenced remote object,

     * written by {@link java.io.ObjectOutput#writeUTF(String)}

     *

     * <li>the port of the referenced remote object,

     * written by {@link java.io.ObjectOutput#writeInt(int)}

     *

     * <li>a client socket factory (object of type

     * <code>java.rmi.server.RMIClientSocketFactory</code>),

     * written by passing it to an invocation of

     * <code>writeObject</code> on the stream instance

     *

     * <li>the data written as a result of calling

     * {link java.rmi.server.ObjID#write(java.io.ObjectOutput)}

     * on the <code>ObjID</code> instance contained in the reference

     *

     * <li>the boolean value <code>false</code>,

     * written by {@link java.io.ObjectOutput#writeBoolean(boolean)}

     *

     * </ul>

     *

     * <p>For <code>"ActivatableRef"</code> with a

     * <code>null</code> nested remote reference:

     *

     * <ul>

     *

     * <li>an instance of

     * <code>java.rmi.activation.ActivationID</code>,

     * written by passing it to an invocation of

     * <code>writeObject</code> on the stream instance

     *

     * <li>a zero-length string (<code>""</code>),

     * written by {@link java.io.ObjectOutput#writeUTF(String)}

     *

     * </ul>

     *

     * <p>For <code>"ActivatableRef"</code> with a

     * non-<code>null</code> nested remote reference:

     *

     * <ul>

     *

     * <li>an instance of

     * <code>java.rmi.activation.ActivationID</code>,

     * written by passing it to an invocation of

     * <code>writeObject</code> on the stream instance

     *

     * <li>the external ref type name of the nested remote reference,

     * which must be <code>"UnicastRef2"</code>,

     * written by {@link java.io.ObjectOutput#writeUTF(String)}

     *

     * <li>the external form of the nested remote reference,

     * written by invoking its <code>writeExternal</code> method

     * with the stream instance

     * (see the description of the external form for

     * <code>"UnicastRef2"</code> above)

     *

     * </ul>

     *

     * <p>For <code>"UnicastServerRef"</code> and

     * <code>"UnicastServerRef2"</code>, no data is written by the

     * <code>writeExternal</code> method or read by the

     * <code>readExternal</code> method.

     */

    private void writeObject(java.io.ObjectOutputStream out)

        throws java.io.IOException

    {

        if (ref == null) {

            throw new java.rmi.MarshalException("Invalid remote object");

        } else {

            String refClassName = ref.getRefClass(out);

            if (refClassName == null || refClassName.length() == 0) {

                /*

                 * No reference class name specified, so serialize

                 * remote reference.

                 */

                out.writeUTF("");

                out.writeObject(ref);

            } else {

                /*

                 * Built-in reference class specified, so delegate

                 * to reference to write out its external form.

                 */

                out.writeUTF(refClassName);

                ref.writeExternal(out);

            }

        }

    }

    /**

     * <code>readObject</code> for custom serialization.

     *

     * <p>This method reads this object's serialized form for this class

     * as follows:

     *

     * <p>The <code>readUTF</code> method is invoked on <code>in</code>

     * to read the external ref type name for the <code>RemoteRef</code>

     * instance to be filled in to this object's <code>ref</code> field.

     * If the string returned by <code>readUTF</code> has length zero,

     * the <code>readObject</code> method is invoked on <code>in</code>,

     * and than the value returned by <code>readObject</code> is cast to

     * <code>RemoteRef</code> and this object's <code>ref</code> field is

     * set to that value.

     * Otherwise, this object's <code>ref</code> field is set to a

     * <code>RemoteRef</code> instance that is created of an

     * implementation-specific class corresponding to the external ref

     * type name returned by <code>readUTF</code>, and then

     * the <code>readExternal</code> method is invoked on

     * this object's <code>ref</code> field.

     *

     * <p>If the external ref type name is

     * <code>"UnicastRef"</code>, <code>"UnicastServerRef"</code>,

     * <code>"UnicastRef2"</code>, <code>"UnicastServerRef2"</code>,

     * or <code>"ActivatableRef"</code>, a corresponding

     * implementation-specific class must be found, and its

     * <code>readExternal</code> method must read the serial data

     * for that external ref type name as specified to be written

     * in the <b>serialData</b> documentation for this class.

     * If the external ref type name is any other string (of non-zero

     * length), a <code>ClassNotFoundException</code> will be thrown,

     * unless the implementation provides an implementation-specific

     * class corresponding to that external ref type name, in which

     * case this object's <code>ref</code> field will be set to an

     * instance of that implementation-specific class.

     */

    private void readObject(java.io.ObjectInputStream in)

        throws java.io.IOException, java.lang.ClassNotFoundException

    {

        String refClassName = in.readUTF();

        if (refClassName == null || refClassName.length() == 0) {

            /*

             * No reference class name specified, so construct

             * remote reference from its serialized form.

             */

            ref = (RemoteRef) in.readObject();

        } else {

            /*

             * Built-in reference class specified, so delegate to

             * internal reference class to initialize its fields from

             * its external form.

             */

            String internalRefClassName =

                RemoteRef.packagePrefix + "." + refClassName;

            Class<?> refClass = Class.forName(internalRefClassName);

            try {

                @SuppressWarnings("deprecation")

                Object tmp = refClass.newInstance();

                ref = (RemoteRef) tmp;

                /*

                 * If this step fails, assume we found an internal

                 * class that is not meant to be a serializable ref

                 * type.

                 */

            } catch (InstantiationException | IllegalAccessException | ClassCastException e) {

                throw new ClassNotFoundException(internalRefClassName, e);

            }

            ref.readExternal(in);

        }

    }

}