java.io.Externalizable Maven / Gradle / Ivy

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; import java.io.ObjectOutput; import java.io.ObjectInput; /** * Only the identity of the class of an Externalizable instance is * written in the serialization stream and it is the responsibility * of the class to save and restore the contents of its instances. * * The writeExternal and readExternal methods of the Externalizable * interface are implemented by a class to give the class complete * control over the format and contents of the stream for an object * and its supertypes. These methods must explicitly * coordinate with the supertype to save its state. These methods supercede * customized implementations of writeObject and readObject methods.
* * Object Serialization uses the Serializable and Externalizable * interfaces. Object persistence mechanisms can use them as well. Each * object to be stored is tested for the Externalizable interface. If * the object supports Externalizable, the writeExternal method is called. If the * object does not support Externalizable and does implement * Serializable, the object is saved using * ObjectOutputStream.
When an Externalizable object is * reconstructed, an instance is created using the public no-arg * constructor, then the readExternal method called. Serializable * objects are restored by reading them from an ObjectInputStream.
* * An Externalizable instance can designate a substitution object via * the writeReplace and readResolve methods documented in the Serializable * interface.
* * @author unascribed * @version 1.15, 02/02/00 * @see java.io.ObjectOutputStream * @see java.io.ObjectInputStream * @see java.io.ObjectOutput * @see java.io.ObjectInput * @see java.io.Serializable * @since JDK1.1 */ public interface Externalizable extends Serializable { /** * The object implements the writeExternal method to save its contents * by calling the methods of DataOutput for its primitive values or * calling the writeObject method of ObjectOutput for objects, strings, * and arrays. * * @serialData Overriding methods should use this tag to describe * the data layout of this Externalizable object. * List the sequence of element types and, if possible, * relate the element to a public/protected field and/or * method of this Externalizable class. * * @param out the stream to write the object to * @exception IOException Includes any I/O exceptions that may occur */ public void writeExternal(java.io.ObjectOutput out) throws IOException; /** * The object implements the readExternal method to restore its * contents by calling the methods of DataInput for primitive * types and readObject for objects, strings and arrays. The * readExternal method must read the values in the same sequence * and with the same types as were written by writeExternal. * * @param in the stream to read data from in order to restore the object * @exception IOException if I/O errors occur * @exception ClassNotFoundException If the class for an object being * restored cannot be found. */ public void readExternal(java.io.ObjectInput in) throws IOException, ClassNotFoundException; }