Hi,
I think I have got some light and help in one of the earlier posts, and I think
ideally it should work out while marshalling the objects to XML. This link
http://www.mail-archive.com/[email protected]/msg02202.html does
provide some good pointers for what I am trying to achieve.
Thanks.
Regards,
Anshuk Pal Chaudhuri
From: Luca Buraggi [mailto:[email protected]]
Sent: Wednesday, May 13, 2009 2:09 PM
To: JiBX users
Subject: Re: [jibx-users] Object Streaming using JIBX
Hi,
I also am facing with a similar problem. More precisely it is the symmetric
problem: I must unmarshall some huge (sometimes greater than 500 Mbytes) XML
files composed by a sequence of the same complex element. Something similar to
this:
---
<list>
<element> ... </element>
<element> ... </element>
<element> ... </element>
...
...
</list>
---
While unmarshalling each single <element> is perfectly feasible, any attempt to
unmarshall the whole file fails due to lack of heap space.
I am not an expert JIBX user, I am still exploring the framework. But I
examined other popular XML binding framework (JAXB and Castor) and I think JIBX
architecture is better and more powerful if applied to such a task.
I am now prototyping and testing a solution based on using the API of the
UnmarshallingContext class (I can't use the IUnmarshallingContext interface
because it hides some methods that are needed, and this is definitely not an
optimal solution, but I have no chance)
This is the scenario:
---
IBindingFactory bfact = BindingDirectory.getFactory(Element.class);
// Very ugly, but ...
UnmarshallingContext uctx = (UnmarshallingContext)
bfact.createUnmarshallingContext();
uctx.setDocument(new FileInputStream("HugeDataFile.xml"), null);
boolean done = false;
// This loop scans the whole input data file
while (done == false) {
if (uctx.isAt(null, "element") {
// The current event is a <element> start tag
Element el = (Element) uctx.unmarshalElement();
// Now process the el object
...
...
} else {
// End of file ?
if (uctx.next() == IXMLReader.END_DOCUMENT) {
done = true;
}
}
}
---
I also will of course appreciate any suggestion or comment ...
Regards,
Luca Buraggi
------------------------------------
Anshuk Pal Chaudhuri ha scritto:
Hi,
I have been working on jibx for quite some time and really appreciate the
philosophy went into building it and how the byte code enhancements helps in
faster marshalling of the objects into XML. I was thinking to evangelize more
into it and was trying to figure out how could the java objects be
marshaled/streamed one at a time rather than marshalling the whole list of
objects. I have defined the scenario details in the below section:
A query is fetched to hit the database which would fetch say 10000 records (in
some defined batches say 500); each record when fetched is populated into a
custom object (some custom value object). Rather than setting the objects
(10000 in this case) into a parent object’s some list or some array list, I was
thinking whether I can marshal the custom value object straight way into the
xml and as more records are fetched, every time the populated object is
marshaled into the same xml.
So in a way, the complete list of objects (one big parent object) which could
have been passed into the jibx marshal only in one time (which would have
consume more memory), every a single object would be marshaled and append in
the same file every time it is being fetched from the object.
I think there are some apis which can be used to achieve something like the
above scenario; like IMarshallingContext. startDocument, IXMLWriter.
startTagClosed, IXMLWriter. endTag
Can anybody let me know your thoughts on this.
Any help is appreciated.
Regards,
Anshuk Pal Chaudhuri
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