Processing an XML "command file"

Question

Hi!
I am planning to implement an application where the middle-tier (a DataWebBean relying on BC4J?) processes XML files.
These XML files would be "command" files to insert/update/delete data in the database - actually they would be very similar to data XML files, but each element having a supplementary attribute indicating whether the element is new, has to be updated or has to be deleted.
Here is an example of what could be such a file (actually this would be a bit more compex, since it would be hierarchical with potentially more than one level - actually "isomorphic" to the structure of a view object - rather than of a table):
<ROWSET name="FLIGHTS">
<ROW action="insert">
<FLIGHT updated="true">AC860</FLIGHT>
<FROM updated="true">Paris</FLIGHT>
</ROW>
<ROW action="update">
<FLIGHT updated="false">AF33</FLIGHT>
<FROM updated="true">New-York</FLIGHT>
</ROW>
<ROW action="delete">
<FLIGHT updated="false">UA111</FLIGHT>
<FROM updated="false">Denver</FLIGHT>
</ROW>
<ROW action="none">
<FLIGHT updated="false">QT40</FLIGHT>
<FROM updated="false">Sydney</FLIGHT>
</ROW>
</ROWSET>
This example tells to add a flight, to update another (notice that only the "FROM" attribute is marked as changed), to delete another and to do nothing with the last one.
I think this is very similar to what XSQL is able to do but is there a way with XSQL to mix inserts, updates and deletes in the same XML file?
If not, I plan to analyse the file with the XML parser and for each node, issue the corresponding command on the underlying View Object.
But since it is a lot of work if I want it to be generic, I'd like to be sure there is no already existing (or more straightforward) way to achieve this... Any opinion or code sharing greatly appreciated!
Thank you!
Serge

Answer 1

If you're using BC4J and XSQL together, then you can leverage the oracle.jbo.xsql.UpdateViewObject action handler that ships with BC4J for use in XSQL pages to make it easy to handle hierarchical XML documents using BC4J view objects.
BC4J view objects can both produce and consume XML documentment using the writeXML() and readXML() API's on oracle.jbo.ViewObject, respectively.
If there are view links in place, then the BC4J XML processing mechanism follows these links to nested, detail information. When you "feed" an existing XML document to the YourViewObject.readXML() method, it automatically processes inserts, updates, and deletes, as well as apply any BC4J business logic that exists in your Entity Objects (if any).
The BC4J Action Handlers make it easy to combine BC4J with XSQL pages without having to write the writeXML() and readXML() calls by hand.