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From Simon Kitching <>
Subject Re: Using Digester to store info into a Map
Date Tue, 20 Jun 2006 11:39:30 GMT
On Thu, 2006-06-15 at 07:43 -0700, Jeff Marendo wrote:
> Simon,
>   Thanks for the reply and helpful information.
>   >>If user is the root level, then you've not got a lot of object in the
>   >>map :-)
>   Yeah, actually, I did have a single file with multiple users listed  within it as you
had suggested,
> but I later changed the design so that  each user would have his own XML file.  Part
of the reason for
> that is because I'm also using Betwixt to save objects as XML.   Just seemed a bit easier
to split the
> users apart into separate files.

Ok, that's a somewhat different problem. I was assuming you'd just
trimmed down your input file to a single user element for the purposes
of this email, and that you really had multiple user elements in a
single input xml file.

But instead you're trying to process a set of xml input files one by
one, each file including one user definition? Digester doesn't provide
any support for processing batches of files, so I presume you're doing:
  for each file to be processed {
    Digester d = new Digester();
    setUpRules(d); // add your custom rules for parsing a user
    User u = (User) d.getRoot();
    // store your user somewhere, eg in a Map
In this case, what's the question about getting *digester* to insert
user objects into maps about?

>   >>The best solution would be to simply *not* use a map.
>   [snip]
>   >>   private Map<Users> userMap = new HashMap<Users>();
>   Can you clarify that for me?  The "<Users>" notation next to  the Map and HashMap
classnames is throwing me off
> , although I think it  just means that they would be storing User instances.

That's java 1.5 generics notation. It just means that the userMap
instance is a map that only permits Users objects to be inserted into it
(just as you assumed).

Actually, I got that syntax wrong (careless!). A map has key and value,
so I should have written:
  private Map<String, User> userMap = new HashMap<String, User>();
which is a map whose keys can only be of type String, and whose values
can only be of type User.

The old-fashioned non-typed maps are technically the same as:
  Map<Object, Object> 
ie accept any Object as key or value.

>   >>Unfortunately, invoking a custom rule when using the xmlrules module
>   >>isn't easy.
>   Yeah, I was afraid of that. 

Actually, I was reading the xmlrules docs to try to answer another
question today and invoking custom rules doesn't seem to be as hard as I
remember. According to the javadoc for the xmlrules *package*, you can
write a special class that instantiates a batch of rules and adds them
to a digester. You then reference that class via:
  <include class="..."/>

Good luck.



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