XML parsing - Thanks Andrew Clarke,info you wanted to answer

Question

Andrew ,
First of all thanks for responding.It was indeed very helpful of you.I have put your questions here just and have answered it
" This is a tricky thing to do. Parsing and processing a document in the database is relatively straightforward. Allowing the user to make changes to it is slightly stickier.
Before we can be of any help you need to give us some more info:
Which version of the database are you using? (9i has lots more functionality)
How are you intending to display the information to the user?
Is your user going to be editing the XML tags or just the content?
Are you using XML SCHEMA or DTD?
Do you know there's an XML forum? (Check the jump to any forum drop down)
1)I am using database :- info
Connected to:
Oracle8i Enterprise Edition Release 8.1.7.0.0 - Production
With the Partitioning option
JServer Release 8.1.7.0.0 - Production
I hope this information is enough.Another thing i wanted to know is how to check for oracle jvm intallation.Because it is needed for oracle xdk installation.
2) I intend to parse the xml file stored as a blob object in the backend and display the information in the front end ( Oracle forms6i) interface.
3) The user sees only the content and can edit only the content ,issuing save command writes back this data into the xml file and saves it back to the database as the blob object.
Yes i know XML discussion forum,but please can you guide me a little in my direction ,i thought it would be more useful to write in this forum (deals with pl/sql).Atleast a lead is enough.
Can you please suggest some help for the questions that i have:-
1)I don't know whether i have oracle JVM installed.The oracle xdk kit install notes say so.So how to check it and get it.Help notes say that a xdk kit for 9i version will also work with 8i version( backward compatibility ).Can you offer some advice on this whether this is possible( The xdkload utility says so.)
2)Is it possible to,after having build a tree thro' parsing process and to go through it accessing the nodes and the values .Also is it possible to write to this tree at the particular point and have the tree saved back to xml document.This will save me a lot of job.Please feel free to help me or atleast suggest some lead points if you know if this can be done.A hyper link ,if you know,which details these steps are also enough.
Regarding the XML schema or DTD ,please give me some more time.
One last question(if i am not bugging you) when the xdkload utility loads the xdk pl/sql package with -dbver to 8i ,will it support all the command in it to be executed on the 8i backend.
(http://technet.oracle.com/support/tech/xml/xdk_plsql/ softwares section)
Andrew ,i will feel really grateful if you can help me with these issues.Anyway Thanks for taking so much efforts in giving me some tips.
Regards
gopal

Answer 1

I hope this information is enough.Another thing i wanted to know is how to check for oracle jvm intallation.Because it is needed for oracle xdk installation.The banner that comes up when you log on shows you that you are running:
JServer Release 8.1.7.0.0 - Production so that means Java is enabled. A good start.
Help notes say that a xdk kit for 9i version will also work with 8i version( backward compatibility ).We are running with XDK 9i in 8173 databases without any major issues. n fact I recommend it, as there are a couple of nasty bugs in the 8i XDK that render it virtually unusable. However there is a whole bunch of functionality in the 9i XDK that relies on the XML datatype that was introduced in the 9i database.
2) I intend to parse the xml file stored as a blob object in the backend and display the information in the front end ( Oracle forms6i) interface.
3) The user sees only the content and can edit only the content ,issuing save command writes back this data into the xml file and saves it back to the database as the blob object.Why not store the data in tables? It is much, much easier to build Forms applications using tables than to build them using XML documents. Disassembling XML documents into tables is relatively straightforward and so is re-constituting them if you ever need to show someone the XML. In Oracle 9i r2 this is what Oracle does by default with the XML datatype.
2)Is it possible to,after having build a tree thro' parsing process and to go through it accessing the nodes and the values .You build the tree using xmlparser.parseClob() followed by xmlparser.getDocument().
You walk the DOM using the methods in the XMLDom package to navigate to any given node. Then you use xmldom.getNodeValue(} to retrieve the data in that node. This only works for nodes of type xmldom.text_node, so you'll need to test for that. It also fails if the node has a null value. Finally bear it mind that according to DOM principles the content of a node is a child[i] of that node.
Given this fragment:
<employee>
    <empno>1234</empno>
</employee>I want to get the employee number. So:[list]
[*]I generate a list of empno nodes using node_list := xmldom.getElementsByTagName(x_doc, 'empno');[*]I navigate to the node I want using el := xmldom.item(node_list, 1)};[*]I then navigate to the text using text_node := xmldom.getFirstChild(el);[*]I navigate to the node I want using emp_no := xmldom.getNodeValue(text_node};[list]
There may be whizzier ways of doing it but this way is clear and it works.
Although the documentation that comes with the XDK isn't that bad you will find some additional info in the onlineshttp://technet.oracle.com/docs/products/oracle9i/doc_library/release2/appdev.920/a96621/adx20ppl.htm#1656. have a look at the domsample.sql script. It's actually quite helpful.
Also is it possible to write to this tree at the particular point and have the tree saved back to xml document.I haven't done this myself, but I would have thought you would write stuff using the method outlined above but using xmldom.setNodeValue. There are various WriteTo... in the xmldom package.
Now for the bad news. None of this works with BLOBs. You have to use CLOBs, VARCHAR2s or external OS files. Sorry.
Good luck, APC