Java Reference
In-Depth Information
The class
Name
can be written to an
ObjectOutputStream
either directly with
writeObject
, or indirectly if it is referenced by an object written to such
a stream. The
name
and
id
fields will be written to the stream; the fields
nextID
,
hashSet
, and
hash
will not be written,
nextID
because it is
static
and the others because they are declared
transient
. Because
hash
is a
cached value that can easily be recalculated from
name
, there is no reas-
on to consume the time and space it takes to write it to the stream.
Default deserialization reads the values written during serialization.
Static fields in the class are left untouchedif the class needs to be loaded
then the normal initialization of the class takes place, giving the static
fields an initial value. Each transient field in the reconstituted object is
set to the default value for its type. When a
Name
object is deserialized,
the newly created object will have
name
and
id
set to the same values as
those of the original object, the static field
nextID
will remain untouched,
and the transient fields
hashSet
and
hash
will have their default values
(
false
and
0
). These defaults work because when
hashSet
is
false
the
value of
hash
will be recalculated.
You will occasionally have a class that is generally serializable but has
specific instances that are not serializable. For example, a container
might itself be serializable but contain references to objects that are not
serializable. Any attempt to serialize a non-serializable object will throw
a
NotSerializableException
.
20.8.3. Serialization and Deserialization Order
Each class is responsible for properly serializing its own statethat is, its
fields. Objects are serialized and deserialized down the type treefrom
the highest-level class that is
Serializable
to the most specific class. This
order is rarely important when you're serializing, but it can be important
when you're deserializing. Let us consider the following type tree for an
HTTPInput
class:
