On 12/18/05, Wendy Smoak <[EMAIL PROTECTED]> wrote: > > On 12/18/05, Rahul Akolkar <[EMAIL PROTECTED]> wrote: > > > I'm not aware of one. Some thoughts that may help, based on my > understanding: > > > > * A <catalog> element (usually the root) can contain any number of > commands. > > * A command may be represented by a single <command> element or a > > <chain> element > > * A <chain> element can contain multiple <command> elements, which > > get executed in order > > Any thoughts on the use of <catalog> as the root element vs. <chains> > as shown in the cookbook examples? > > Using <catalog> puts the commands into the default catalog which is > retrieved with CatalogFactory.getInstance().getCatalog(). > > Using <chains> seems to do something else. I haven't figured out if > the commands are going somewhere else, if the config file just isn't > being parsed, (or if I'm imagining it.)
Chain tries to be incredibly (perhaps insanely :-) flexible about what element and attribute names it recognizes. As I mentioned in a previous message, the code that actually decides this is the instance of ConfigRuleSet that you use to configure the Digester that parses the XML configuration resources. The cookbook page on the web site illustrates what to use when you take the defaults. http://jakarta.apache.org/commons/chain/cookbook.html In addition, you are also running into a semantics issue caused by the development history of Chain. Originally, there was no concept of catalogs; all the commands and chains were registered together, and the <catalog> syntax was sufficient for that. Later on, it became clear that multiple catalogs were a very useful gadget. (As a side note, you'll smile when you see whose idea *that* was, and did a lot of the heavy lifting :-): http://issues.apache.org/bugzilla/show_bug.cgi?id=31566 As usual in Apache land, we tried to stay backwards compatible with the old syntax, even though it ideally would have gotten pulled before the 1.0release. I would suggest sticking with the syntax that supports multiple catalogs, but with one final warning -- the actual element name of the outermost element of your document does not really matter. The Digester rules are initialized with patterns like "*/chain" and "*/command" that match wherever in the XML document hierarchy they are found. Thanks, > -- > Wendy Craig
