Modify XML via Python problem

Question

Hi,
Using this: http://www.oracle.com/technology/documentation/berkeley-db/xml/gsg_xml/cxx/modifydocument.html as my inspiration, I am attempting to update a value in dbxml via th Python bindings. The XML document in question looks something like:
<foo><bar>123</bar></foo>
and my code looks like:
def open(self, dbname):
self.dbname = dbname
self.manager = dbxml.XmlManager()
self.container = self.manager.openContainer(self.dbname)
self.qcontext = self.manager.createQueryContext()
self.ucontext = self.manager.createUpdateContext()
self.mcontext = self.manager.createModify()
self.isopen = True
def get(self, x):
if self.isopen == False: return None
query = "collection('" + self.dbname + "')" + x
expression = self.manager.prepare(query, self.qcontext)
for object in expression.execute(self.qcontext, 0): return object
def set(self, object, query, value):
if self.isopen == False: return
if object == None: return
select = self.manager.prepare(query, self.qcontext);
self.mcontext.addUpdateStep(select, value);
self.mcontext.execute(object.asDocument(), self.qcontext, self.ucontext); # XXX
The object returned by "get" is "foo" using a query string of "/foo" (which works just fine). This object is in turned passed to "set" using a query string of "/foo/bar".
The trouble area is marked with "XXX" above. The error message is:
File "/opt/dbxml-2.2.13/lib/python/dbxml.py", line 748, in execute
def execute(*args): return dbxml.XmlModifyexecute(*args)
NotImplementedError: No matching function for overloaded 'XmlModify_execute'
If I remove "asDocument()", then the error message is:
File "/opt/dbxml-2.2.13/lib/python/dbxml.py", line 748, in execute
def execute(*args): return dbxml.XmlModifyexecute(*args)
RuntimeError: Error: XmlModify::execute: Cannot perform a modification on an XmlValue that isn't either Node or Document type
Any idea what I am doing wrong? Much thanks.
-Tom

Answer 1

Tom,
Your objects are not of the correct types for the various overloads.
You can determine what type they should be by looking at the
C++ documentation -- the Python bindings are quite similar.
Here's a working script for you to look at as well (I"m sure you'll
have to reformat to get the indentation correct):
from bsddb3.db import *
from dbxml import *
from _dbxml import *
book_content = r"<book><title>Knowledge Discovery in Databases.</title></book>"
book_name = r"book1"
def remove_database():
    """Removes the databases so we can start with a fresh environment for
    each test."""
    import os, glob
    databases = ["test", "test1", "test2"]
    for database in databases:
        files = glob.glob(database + "*.dbxml")
        files += glob.glob("__db*")
        files += glob.glob("log.*")
        for file in files:
            os.remove(file)
def doModify():
    mgr = XmlManager()
    uc = mgr.createUpdateContext()
    container = mgr.createContainer("test.dbxml")
    container.putDocument(book_name, book_content, uc)
    qc = mgr.createQueryContext()
    results = mgr.query("collection('test.dbxml')/book", qc)
    # print original document
    for value in results:
        document = value.asDocument()
        print document.getName(), "=", value.asString()
    mod = mgr.createModify()
    exp = mgr.prepare("./title", qc)
    mod.addInsertAfterStep(exp, XmlModify.Element, "new", "text")
    # apply modification to results (original document),
    # update, and then look at new content
    results.reset()
    for value in results:
     mod.execute(value, qc, uc)
        document = value.asDocument()
     container.updateDocument(document, uc)
    doc1 = container.getDocument(book_name)
    print "after: ", document.getContent()
if __name__ == "__main__":
    import sys
    remove_database()
    doModify()Regards,
George