Thanks Simon, I figured this would be the case, but I wanted to make sure.
The solution I have come up with is to make a custom rule that parses that element into a helper class, then uses the VariableFactory to instantiate the right Variable subclass. Just to make sure I have this right in begin() I am pushing an instance of the helper class (DefaultVariable) on the digester stack. In end() I am popping it, creating a new subclass and adding it to the list (which was one above on the stack). At the end of end() should I be pushing this new Variable back on the stack after I add it to the list (top of the stack), or is it correct to just consume it? Thanks Chris On 9/13/06, Simon Kitching <[EMAIL PROTECTED]> wrote:
Hi Chris, On Tue, 2006-09-12 at 18:01 -0700, Chris Cheshire wrote: > I have to process an XML file that contains (in part) the following structure > <variables> > <Variable> > <ID>...</ID> > <Name>...</Name> > <Instance>...</Instance> > <Value>...</Value> > </Variable> > </variables> > > I have a predefined list of variables based upon their ID, an abstract > Variable class, and then concrete subclasses of these for each valid > ID. > > Variable contains a static method Variable getInstance(int ID) that > creates a new variable subclass based upon the ID (the id-subclass > mapping is based upon a properties file). > > The FactoryCreateRule allows for creation of classes based via a > factory providing the identifiying parameter is an XML attribute. In > this case it is not. It is a sub-element, I have no control over that. > > How can I use the FactoryCreateRule to call getInstance(int ID) in my > Variable class when I need to extract the ID from a nested element not > an attribute? This is quite a common question, and really deserves an FAQ entry. In short, you can't. Digester is a SAX-based system, and with SAX there is no "look ahead" option. One possible solution is to use an XSLT stylesheet to pre-process your xml to move all the data needed to determine the object type into attributes of the element that triggers the object creation. Then the FactoryCreateRule can be used as normal. It might be possible to create a variant of the FactoryCreateRule that creates a hashmap or similar when the start element is found, store child objects in that hashmap until the end element is found, then looks into the hashmap to get the data to determine the type of object to instantiate and copy the hashmap contents into properties of the created object. It all seems rather clumsy/fragile though. If you do wish to try this, and get it to work then please put that info in the digester wiki as you're not the first person to ask about this. Regards, Simon --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
--------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
