Document in xml - Not serializable? Well, I need to cache it.

Question

Can anyone tell me how can I serialize DOM Document.
When we try to put it in cache, cache complains that it
is not serializable (I believe ElementImpl is not Serializable).
In javadoc it shows serializable form for this Element, but when I look in the source it does not implements Serializable (and none of its parent interfaces).
My question is this?
Does anyone know how to serialize Document.
(I do need to Serialize Document, not XML.In my case it
is too expensive to parse XML every time I come back
from cache)
How do I use Serializable form of one class or interface?
Thank You.
Edmon

Answer 1

Sorry about not being very helpful earlier. The number of people who submit JDC forum questions without reading even the elementary intro docs is rather staggering, IMHO. Here is something more detailed:
(a) "Serialized form" of a class as found in javadoc has little to do with whether or not the class has been declared as Serializable by the implementor.
(b) what matters to Java serialization is whether the object in question is runtime-Serializable. In your particular case, org.w3c.dom.Document is an interface and it was not declared as Serializable by W3C. Perhaps justifiably so, because that imposes unfair requirements on parser implementors [seeing that not everybody is expected to want to serialize a DOM tree the way you do].
However, a particular parser implementation is free to make its Document implementation class as Serializable. If that is the case, writeObject(obj) will succeed even if "obj" variable is of Document [not Serializable] type but happens to point to a Serializable implementation class.
But, if you rely on this behavior you are locking yourself into that particular parser implementation. Should you choose a different XML parser in the future you will see serialization errors at runtime. With things like JAXP and a variety of XML parsers available this perhaps is not the way to go.
Things would have been different if Document was declared to implement Serializable. Then all XML parsers would have had a standard behavior for the DOM trees they produced, regardless of implementation details. This is not the case, though.
Vlad.