On Wednesday, September 3, 2003, at 08:07 AM, James Strachan wrote:
On Tuesday, September 2, 2003, at 11:22 pm, Dain Sundstrom wrote:
On Tuesday, September 2, 2003, at 07:44 AM, James Strachan wrote:
On Tuesday, September 2, 2003, at 12:56 am, Dain Sundstrom wrote:I think we should just use Digester directly.
Why?
The introspection makes me wary. If they change the rules, all of our stuff breaks.
What do you mean 'they'. We're talking about getters, setters & adder methods here. I can't see the Java Beans spec changing any time soon.
By they I mean the people writing Betwixt.
We write Betwixt (i.e. Apache folks). I'm the guilty person who started it. Be that as it may - I don't see the introspection rules changing ever for backwards compatibility (unless explicitly configured to be different).
You are implying there is a simple well understood mapping between xml and java beans.
Yes. Which can be overridden either at the digester level or at the betwixt level with a simple XML config file on a per class basis.
XML names tend to have dashes in them and some times the structure of the (spec) documents is not how you want you beans.
There's a little pluggable strategy called NameMapper for this kind of thing...
http://jakarta.apache.org/commons/betwixt/apidocs/org/apache/commons/ betwixt/strategy/package-summary.html
so if you just add a HyphenatedNameMapper onto your XMLIntrospector it'll all just work. I suspect the same XMLIntrospector will work for all the 7 XSDs
Besides that, I think the "digester glue" code you complain about below is simple to read and understand.
Go right ahead if you want - I'm just offering us not having to write 7 different digesters for the 7 J2EE schemas.
Relax James, it is not a big deal.
Ditto - I don't personally care either way. I was just trying to avoid the work to write 7 Digesters.
It is like typeing in the API interfaces; it is a few hours of work up front and you get a lot more control.
Same control. Just more redundant code. But I really don't mind. Go pure digester if you like.
What happens when you have exceptions and non trivial mappings. For example, I have a place where I named an xml attribute named "class", but the class attribute is named "name" because the spec calls it that (and the spec is wrong).
Betwixt just makes a special kind of Digester. Its still a Digester so you can still happily add any wierd/wacky rules you want. Also for doing simple property / XML changes there's a little .betwixt mapping XML file you can do this with. Though I doubt we'll need to worry about that - we can just code the beans right (so they use the same property names as the XML elements/attributes).
That is my exact problem... In this case the beans are required by the JMX specification and they got the naming wrong.
Which beans are we talking about? I've been talking about the 7 XSD schemas. Are you talking about something else? You're not off in MLET land or something are you?
The JMX spec tries to reuse a base class for MBeanAttributeInfo, MBeanOperationInfo and MBeanNotificationInfo. They all have a field called name, which makes since for attribute an operation, but for notification the spec says that name caries the java type of the notification object. The over user of inheritance here has caused the property to have the wrong name. In the xml I rename the property to name as it is easier for out users to understand.
My guess is there will be a ton of special mappings for the j2ee specs as the descriptors tend to be poorly designed.
I don't follow. e.g. in ejb-jar or web.xml what are the issues? I thought we were talking about beans to represent the 7 XSD schemas in J2EE?
Also note that Digester is read only - it cannot generate XML. Betwixt defaults digester rules to parse XML and can generate XML from the beans if required.
Cool. Can Digester do this or does digester do something special to make it happen?
No. Thats what betwixt is for - its the other half of digester - to allow beans to generate XML - and as an automatic way of generating digester rules from beans which use getter / setter and adder > methods.
Yes, but how does it do it.
Betwixt just makes a normal Digester - it is-a digester - it defaults the Rules in Digester from a bean introspection defaults via the XMLIntrospector.
So there's nothing taken away - you can still add custom digester rules yourself by hand.
Is it building a reverse digester using Digester or does it have it's own logic that knows how to do it? I like that feature, but not the rest of Betwixt.
There is no digester feature to output XML. So the output of XML is a purely betwixt thing. Basically Betwixt creates a little XMLBeanInfo class which describes how to map it to XML and this is used to go XML -> bean (defaulting digester rules) and to go bean -> XML.
James ------- http://radio.weblogs.com/0112098/
