On Wed, 2004-02-11 at 10:48, robert burrell donkin wrote:
> hi Christian
>
> i think that there are two general approach to solving this with
> digester.
There is a third: Create a class "Definitions" which is a wrapper around
the HashMap:
public class Definitions {
private HashMap defs = new HashMap();
public void setNext(DefinitionBean db) { defs.put(db.getKey(), db); }
public HashMap getMap() { return defs; }
}
You can then use the standard SetNextRule.
> the first is to create a custom Rule implementation. this should be
> very easy in this case (just put the code you've already got into begin
> and then get the ordering right).
Yep, creating a Rule to solve this specific problem shouldn't be hard.
Digester is *designed* to allow users to add custom rules.
Christian: as Robert said, your pseudocode is pretty good already. You
really just need to declare a class extending Rule, then put your
pseudocode into the end() method.
Note that digester.peek(0) returns top-of-stack (newest object), and
digester.peek(1) returns next-to-top (next-to-newest) object; this is
probably tidier than your pseudocode which used pop() and push().
>
> the second is to use a adapted version of CallMethodRule which calls a
> method on the root object (rather than the top). this should be easy to
> do and probably should already by in digester. (anyone fancy
> volunteering to develop this one for the ASF?)
This doesn't sound too difficult - I'll have a stab at creating a
suitable class tonight.
It seems that what is needed is something like SetNextRule (which builds
parent/child relationships) except that the params need to be more
flexible - not just the object on top of the stack.
I suggest creating a "CallNextMethodRule" which behaves identically to
CallMethodRule except the target object is grabbed with peek(1) rather
than peek(). Obviously copy/paste should be avoided, so a "strategy" or
"template method" or similar approach could be used to "extend" the
existing CallMethodRule functionality to allow selecting the target
object from locations other than top-of-stack.
I think it would be nice to just add a "target object offset" param to
the CallMethodRule constructor (default value=0) to select the target
object on the stack, but there are so many constructors on
CallMethodRule already :-(
Any comments, Robert?
Regards,
Simon
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