java.io.Serializable Maven / Gradle / Ivy

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This work corresponds to the API signatures of JSR 219: Foundation Profile 1.1. In the event of a discrepency between this work and the JSR 219 specification, which is available at http://www.jcp.org/en/jsr/detail?id=219, the latter takes precedence. */ package java.io; /** * Serializability of a class is enabled by the class implementing the * java.io.Serializable interface. Classes that do not implement this * interface will not have any of their state serialized or * deserialized. All subtypes of a serializable class are themselves * serializable. The serialization interface has no methods or fields * and serves only to identify the semantics of being serializable.

* * To allow subtypes of non-serializable classes to be serialized, the * subtype may assume responsibility for saving and restoring the * state of the supertype's public, protected, and (if accessible) * package fields. The subtype may assume this responsibility only if * the class it extends has an accessible no-arg constructor to * initialize the class's state. It is an error to declare a class * Serializable if this is not the case. The error will be detected at runtime.

* * During deserialization, the fields of non-serializable classes will * be initialized using the public or protected no-arg constructor of * the class. A no-arg constructor must be accessible to the subclass * that is serializable. The fields of serializable subclasses will * be restored from the stream.

* * When traversing a graph, an object may be encountered that does not * support the Serializable interface. In this case the * NotSerializableException will be thrown and will identify the class * of the non-serializable object.

* * Classes that require special handling during the serialization and * deserialization process must implement special methods with these exact * signatures:

* *

 * private void writeObject(java.io.ObjectOutputStream out)
 *     throws IOException
 * private void readObject(java.io.ObjectInputStream in)
 *     throws IOException, ClassNotFoundException;
 * 

* * 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 default mechanism for saving * the Object's fields can be invoked by calling * out.defaultWriteObject. The method does not need to concern * itself with the state belonging to its 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.

* * The readObject method is responsible for reading from the stream and * restoring the classes fields. It may call in.defaultReadObject to invoke * the default mechanism for restoring the object's non-static and non-transient * fields. The defaultReadObject method uses information in the stream to * assign the fields of the object saved in the stream with the correspondingly * named fields in the current object. This handles the case when the class * has evolved to add new fields. The method does not need to concern * itself with the state belonging to its 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.

* * Serializable classes that need to designate an alternative object to be * used when writing an object to the stream should implement this * special method with the exact signature:

* *

 * ANY-ACCESS-MODIFIER Object writeReplace() throws ObjectStreamException;
 * 

* * This writeReplace method is invoked by serialization if the method * exists and it would be accessible from a method defined within the * class of the object being serialized. Thus, the method can have private, * protected and package-private access. Subclass access to this method * follows java accessibility rules.

* * Classes that need to designate a replacement when an instance of it * is read from the stream should implement this special method with the * exact signature.

* *

 * ANY-ACCESS-MODIFIER Object readResolve() throws ObjectStreamException;
 *