Effective Java

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CHAPTER 12
SERIALIZATION
348
Using the default serialized form when an object’s physical representa-
tion differs substantially from its logical data content has four disadvantages:
•
It permanently ties the exported API to the current internal representa-
tion.
In the above example, the private 
StringList.Entry
class becomes part
of the public API. If the representation is changed in a future release, the
StringList
class will still need to accept the linked list representation on input
and generate it on output. The class will never be rid of all the code dealing
with linked list entries, even if it doesn’t use them anymore.
•
It can consume excessive space.
In the above example, the serialized form
unnecessarily represents each entry in the linked list and all the links. These
entries and links are mere implementation details, not worthy of inclusion in
the serialized form. Because the serialized form is excessively large, writing it
to disk or sending it across the network will be excessively slow.
•
It can consume excessive time.
The serialization logic has no knowledge of
the topology of the object graph, so it must go through an expensive graph
traversal. In the example above, it would be sufficient simply to follow the
next
references.
•