Java in a Nutshell, 5th Edition

Name

ObjectOutputStream.PutField

Synopsis

This class holds values of named fields and allows them to be written to an ObjectOutputStream during the process of object serialization. It gives the programmer precise control over the serialization process and is typically used when the set of fields defined by a class does not match the set of fields (and the serialization stream format) defined by the original implementation of the class. In other words, ObjectOutputStream.PutField allows the implementation of a class to change without breaking serialization compatibility.

In order to use the PutField class, you typically define a private static serialPersistentFields field that refers to an array of ObjectStreamField objects. This array defines the set of fields written to the ObjectOutputStream and therefore defines the serialization format. If you do not declare a serialPersistentFields field, the set of fields is all fields of the class, excluding static and transient fields.

In addition to the serialPersistentFields field, your class must also define a private writeObject( ) method that is responsible for the custom serialization of your class. In this method, call the putFields( ) method of ObjectOutputStream to obtain an ObjectOutputStream.PutField object. Once you have this object, use its various put( ) methods to specify the names and values of the field to be written out. The set of named fields should match those specified by serialPersistentFields. You may specify the ...