The AbstractObjectOutputStream.java Java example source code
/*
* Copyright (c) 1998, 2004, 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.
*
* 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.
*/
/*
*
*
*/
import java.io.*;
import java.security.*;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.lang.reflect.InvocationTargetException;
import java.io.IOException;
import java.io.OutputStream;
import java.io.ObjectOutputStream;
/**
* This class provides a means for a subclass to re-implement Serialization
* while preserving the existing public API to Serialization. A complimentary
* subclass of AbstractObjectInputStream must also be implemented to
* deserializa the new implementation.<p>
*
* Since serialization must override java access rules in order to
* access private, protected and package accessible Serializable fields,
* only trusted classes are allowed to subclass AbstractObjectInputStream.
* Subclasses of AbstractObjectOututStream must have SerializablePermission
* "enableAbstractSubclass" or this constructor will throw a
* SecurityException.Implementations of this class should protect themselves
* from being subclassed in a way that will provide access to object
* references and other sensitive info. Specifically, writeObjectOverride()
* should be made final.
*
* A subclass of AbstractObjectOutputStream writes primitive data types
* and graphs of Java objects to an ObjectOutputStream. The objects can be read
* (reconstituted) using he complimentary subclass of AbstractObjectInputStream.<p>
* Persistent storage of objects can be accomplished by using a file for
* the stream. If the stream is a network socket stream, the objects can
* be reconstituted on another host or in another process. <p>
*
* Only objects that support the java.io.Serializable interface can be
* written to streams.<p>
*
* The method <STRONG>writeObjectOverride is used to write an object
* to the stream. Any object, including Strings and arrays, is
* written with writeObject. Multiple objects or primitives can be
* written to the stream. The objects must be read back from the
* corresponding subclass of AbstractObjectInputstream with the same types
* and in the same order as they were written.<p>
*
* Primitive data types can also be written to the stream using the
* appropriate methods from DataOutput. Strings can also be written
* using the writeUTF method.<p>
*
* The default serialization mechanism for an object is defined by
* defaultWriteObject(). References to other objects
* (except in transient or static fields) cause those objects to be
* written also. Multiple references to a single object are encoded
* using a reference sharing mechanism so that graphs of objects can
* be restored to the same shape as when the original was written. <p>
*
* Classes that require special handling during the serialization and deserialization
* process must implement special methods with these exact signatures: <p>
*
* <PRE>
* private void readObject(java.io.ObjectInputStream stream)
* throws IOException, ClassNotFoundException;
* private void writeObject(java.io.ObjectOutputStream stream)
* throws IOException
* </PRE>
* The writeObject method is responsible for writing the state of
* the object for its particular class so that the corresponding
* readObject method can restore it.
* The method does not need to concern itself with the
* state belonging to the object's superclasses or subclasses.
* State is saved by writing the individual fields to the ObjectOutputStream
* using the writeObject method or by using the methods for
* primitive data types supported by DataOutput. <p>
*
* Serialization does not write out the fields of any object that does
* not implement the java.io.Serializable interface. Subclasses of
* Objects that are not serializable can be serialized. In this case
* the non-serializable class must have a no-arg constructor to allow
* its fields to be initialized. In this case it is the
* responsibility of the subclass to save and restore the state of the
* non-serializable class. It is frequently the case that the fields
* of that class are accessible (public, package, or protected) or
* that there are get and set methods that can be used to restore the
* state. <p>
*
* Serialization of an object can be prevented by implementing writeObject
* and readObject methods that throw the NotSerializableException.
* The exception will be caught by the ObjectOutputStream and abort the
* serialization process.
*
* Implementing the Externalizable interface allows the object to
* assume complete control over the contents and format of the object's
* serialized form. The methods of the Externalizable interface,
* writeExternal and readExternal, are called to save and restore the
* objects state. When implemented by a class they can write and read
* their own state using all of the methods of ObjectOutput and
* ObjectInput. It is the responsibility of the objects to handle any
* versioning that occurs.
*
* @author Joe Fialli
*
* @see java.io.ObjectOutputStream
* @see java.io.DataOutput
* @see java.io.Serializable
* @see java.io.Externalizable
* @see java.io.Replaceable
* @see java.io.ext.AbstractObjectInputStream
*
* @since JDK1.2
*/
abstract public class AbstractObjectOutputStream extends ObjectOutputStream
{
protected OutputStream out;
/* Stream Management Methods. */
/**
* Creates an ObjectOutputStream that writes to the specified OutputStream.
*
* Add the following line to the security policy file to enable
* subclassing.
*
* <PRE>
* permission SerializablePermission "enableAbstractSubclass" ;
* </PRE>
*
* @exception IOException Any exception thrown by the underlying OutputStream.
* @see java.io.ObjectOutputStream#writeStreamHeader()
*/
public AbstractObjectOutputStream(OutputStream out) throws IOException {
this.out = out;
}
abstract public void reset() throws IOException;
abstract protected void drain() throws IOException;
abstract public void close() throws IOException;
/*******************************************************************/
/* Write Objects to Stream */
/**
* Write the specified object to a subclass of AbstractObjectOutputStream.<p>
*
* NOTE: The override method of this class should have the modifier final.<p>
*
* Default serialization for a class can be
* overridden by defining writeObject and the readObject methods
* for the Serializable class. Objects referenced by this object are
* written transitively so that a complete equivalent graph of objects
* can be reconstructed by an ObjectInputStream. <p>
*
* This method must implement the substitution semantics on the
* object to be written, write Externalizable objects with its classes
* override of writeExternal, and it must call annotateClass when
* writing an ObjectStreamClass to the stream.
*
* Exceptions can be thrown for problems with the OutputStream and
* for classes that should not be serialized.
*
* For security's sake, any overrides of this method should be final.
* Serialization typically needs to disable java access rules
* to serialize private, protected and package accessible Serializable
* fields. This method gets called for ALL Serializable objects.
*
* @exception InvalidClassException Something is wrong with a class used by
* serialization.
* @exception NotSerializableException Some object to be serialized does not
* implement the java.io.Serializable interface.
* @exception IOException Any exception thrown by the underlying OutputStream.
* @see java.io.Externalizable
* @see java.io.ObjectOutputStream#replaceObject(Object)
* @see java.io.Replaceable
* @see java.io.ObjectOutputStream#annotateClass(Class)
*/
protected void writeObjectOverride(Object obj)
throws IOException
{
}
/**
* Write the Serializable fields of the current object to this stream.<p>
*
* Note: The object being serialized is not passed to this method.
* For security purposes, the initial implementation maintained
* the state of the last object to be passed to writeObject and
* only allowed this method to be invoked for this object.<p>
*
* @exception NotActiveException Thrown if a writeObject method is not
* active.
*/
abstract public void defaultWriteObject() throws IOException;
/*************************************************************/
/* Use the methods of PutField to map between Serializable fields
* and actual fields of a Serializable class.
*/
abstract public ObjectOutputStream.PutField putFields() throws IOException;
/**
* Note: The PutField being serialized is not passed to this method.
* For security purposes, the initial implementation maintained
* the state of the last putFields call and
* only allowed this method to be invoked for that PutFields object.
*/
abstract public void writeFields() throws IOException;
abstract protected boolean enableReplaceObject(boolean enable) throws SecurityException;
/*******************************************************************/
/* Write Primitive Data to stream. DataOutput methods. */
abstract public void write(int data) throws IOException;
abstract public void write(byte b[]) throws IOException;
abstract public void write(byte b[], int off, int len) throws IOException;
abstract public void writeBoolean(boolean data) throws IOException;
abstract public void writeByte(int data) throws IOException;
abstract public void writeShort(int data) throws IOException;
abstract public void writeChar(int data) throws IOException;
abstract public void writeInt(int data) throws IOException;
abstract public void writeLong(long data) throws IOException;
abstract public void writeFloat(float data) throws IOException;
abstract public void writeDouble(double data) throws IOException;
abstract public void writeBytes(String data) throws IOException;
abstract public void writeChars(String data) throws IOException;
abstract public void writeUTF(String data) throws IOException;
};
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