2362N/A * Copyright (c) 1996, 2005, Oracle and/or its affiliates. All rights reserved. 0N/A * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 0N/A * This code is free software; you can redistribute it and/or modify it 0N/A * under the terms of the GNU General Public License version 2 only, as 2362N/A * published by the Free Software Foundation. Oracle designates this 0N/A * particular file as subject to the "Classpath" exception as provided 2362N/A * by Oracle in the LICENSE file that accompanied this code. 0N/A * This code is distributed in the hope that it will be useful, but WITHOUT 0N/A * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 0N/A * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 0N/A * version 2 for more details (a copy is included in the LICENSE file that 0N/A * accompanied this code). 0N/A * You should have received a copy of the GNU General Public License version 0N/A * 2 along with this work; if not, write to the Free Software Foundation, 0N/A * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 2362N/A * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 2362N/A * or visit www.oracle.com if you need additional information or have any 0N/A * Serializability of a class is enabled by the class implementing the 0N/A * java.io.Serializable interface. Classes that do not implement this 0N/A * interface will not have any of their state serialized or 0N/A * deserialized. All subtypes of a serializable class are themselves 0N/A * serializable. The serialization interface has no methods or fields 0N/A * and serves only to identify the semantics of being serializable. <p> 0N/A * To allow subtypes of non-serializable classes to be serialized, the 0N/A * subtype may assume responsibility for saving and restoring the 0N/A * state of the supertype's public, protected, and (if accessible) 0N/A * package fields. The subtype may assume this responsibility only if 0N/A * the class it extends has an accessible no-arg constructor to 0N/A * initialize the class's state. It is an error to declare a class 0N/A * Serializable if this is not the case. The error will be detected at 0N/A * During deserialization, the fields of non-serializable classes will 0N/A * be initialized using the public or protected no-arg constructor of 0N/A * the class. A no-arg constructor must be accessible to the subclass 0N/A * that is serializable. The fields of serializable subclasses will 0N/A * be restored from the stream. <p> 0N/A * When traversing a graph, an object may be encountered that does not 0N/A * support the Serializable interface. In this case the 0N/A * NotSerializableException will be thrown and will identify the class 0N/A * of the non-serializable object. <p> 0N/A * Classes that require special handling during the serialization and 0N/A * deserialization process must implement special methods with these exact 0N/A * private void writeObject(java.io.ObjectOutputStream out) 0N/A * throws IOException 0N/A * private void readObject(java.io.ObjectInputStream in) 0N/A * throws IOException, ClassNotFoundException; 0N/A * private void readObjectNoData() 0N/A * throws ObjectStreamException; 0N/A * <p>The writeObject method is responsible for writing the state of the 0N/A * object for its particular class so that the corresponding 0N/A * readObject method can restore it. The default mechanism for saving 0N/A * the Object's fields can be invoked by calling 0N/A * out.defaultWriteObject. The method does not need to concern 0N/A * itself with the state belonging to its superclasses or subclasses. 0N/A * State is saved by writing the individual fields to the 0N/A * ObjectOutputStream using the writeObject method or by using the 0N/A * methods for primitive data types supported by DataOutput. 0N/A * <p>The readObject method is responsible for reading from the stream and 0N/A * restoring the classes fields. It may call in.defaultReadObject to invoke 0N/A * the default mechanism for restoring the object's non-static and 0N/A * non-transient fields. The defaultReadObject method uses information in 0N/A * the stream to assign the fields of the object saved in the stream with the 0N/A * correspondingly named fields in the current object. This handles the case 0N/A * when the class has evolved to add new fields. The method does not need to 0N/A * concern itself with the state belonging to its superclasses or subclasses. 0N/A * State is saved by writing the individual fields to the 0N/A * ObjectOutputStream using the writeObject method or by using the 0N/A * methods for primitive data types supported by DataOutput. 0N/A * <p>The readObjectNoData method is responsible for initializing the state of 0N/A * the object for its particular class in the event that the serialization 0N/A * stream does not list the given class as a superclass of the object being 0N/A * deserialized. This may occur in cases where the receiving party uses a 0N/A * different version of the deserialized instance's class than the sending 0N/A * party, and the receiver's version extends classes that are not extended by 0N/A * the sender's version. This may also occur if the serialization stream has 0N/A * been tampered; hence, readObjectNoData is useful for initializing 0N/A * deserialized objects properly despite a "hostile" or incomplete source 0N/A * <p>Serializable classes that need to designate an alternative object to be 0N/A * used when writing an object to the stream should implement this 0N/A * special method with the exact signature: <p> 0N/A * ANY-ACCESS-MODIFIER Object writeReplace() throws ObjectStreamException; 0N/A * This writeReplace method is invoked by serialization if the method 0N/A * exists and it would be accessible from a method defined within the 0N/A * class of the object being serialized. Thus, the method can have private, 0N/A * protected and package-private access. Subclass access to this method 0N/A * follows java accessibility rules. <p> 0N/A * Classes that need to designate a replacement when an instance of it 0N/A * is read from the stream should implement this special method with the 0N/A * exact signature.<p> 0N/A * ANY-ACCESS-MODIFIER Object readResolve() throws ObjectStreamException; 0N/A * This readResolve method follows the same invocation rules and 0N/A * accessibility rules as writeReplace.<p> 0N/A * The serialization runtime associates with each serializable class a version 0N/A * number, called a serialVersionUID, which is used during deserialization to 0N/A * verify that the sender and receiver of a serialized object have loaded 0N/A * classes for that object that are compatible with respect to serialization. 0N/A * If the receiver has loaded a class for the object that has a different 0N/A * serialVersionUID than that of the corresponding sender's class, then 0N/A * deserialization will result in an {@link InvalidClassException}. A 0N/A * serializable class can declare its own serialVersionUID explicitly by 0N/A * declaring a field named <code>"serialVersionUID"</code> that must be static, 0N/A * final, and of type <code>long</code>:<p> 0N/A * ANY-ACCESS-MODIFIER static final long serialVersionUID = 42L; 0N/A * If a serializable class does not explicitly declare a serialVersionUID, then 0N/A * the serialization runtime will calculate a default serialVersionUID value 0N/A * for that class based on various aspects of the class, as described in the 0N/A * Java(TM) Object Serialization Specification. However, it is <em>strongly 0N/A * recommended</em> that all serializable classes explicitly declare 0N/A * serialVersionUID values, since the default serialVersionUID computation is 0N/A * highly sensitive to class details that may vary depending on compiler 0N/A * implementations, and can thus result in unexpected 0N/A * <code>InvalidClassException</code>s during deserialization. Therefore, to 0N/A * guarantee a consistent serialVersionUID value across different java compiler 0N/A * implementations, a serializable class must declare an explicit 0N/A * serialVersionUID value. It is also strongly advised that explicit 0N/A * serialVersionUID declarations use the <code>private</code> modifier where 0N/A * possible, since such declarations apply only to the immediately declaring 0N/A * class--serialVersionUID fields are not useful as inherited members. Array 0N/A * classes cannot declare an explicit serialVersionUID, so they always have 0N/A * the default computed value, but the requirement for matching 0N/A * serialVersionUID values is waived for array classes. 0N/A * @author unascribed 0N/A * @see java.io.ObjectOutputStream 0N/A * @see java.io.ObjectInputStream 0N/A * @see java.io.ObjectOutput 0N/A * @see java.io.ObjectInput 0N/A * @see java.io.Externalizable