[Digester] Converting String value of an attribute to array of integers

[Siddharth Mathur <sm...@nellymoser.com>]

Dear all,

I am trying to use Digester to read my own XML format (shown below) and
convert it to correctly initialized objects. 

<List>

<A ID="1" author="Home made">
	<range>90</range>
</A>

<B ID="2" author="Apple Inc." depends="1">
	<bitrate>90</range>
</B>

[...more entries here]

<C ID="7" author="CT" depends="4,6">
	<flavour>AAC</range>
</C>

</List>


Classes A, B, C are all derived from a parent class which has three
properties:
i) ID (integer)
ii) author (String)
iii) depends (array of IDs i.e integers)

Digester makes it very easy to create setter and getter methods and read in
(i) and (ii) above. But how do I modify the default Rule so that the String
value of the "depends" attribute is converted to an array of integers
property? I will be happy to reformat the depends="4,6" part if required. 

I currently use d.addSetProperties("List/A") to read in my other attributes.


Thank you for your time and patience,
Siddharth


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Re: [Digester] Converting String value of an attribute to array of integers

[Craig McClanahan <cr...@apache.org>]

On 2/17/06, Simon Kitching <sk...@apache.org> wrote:
>
>
> Actually, SetPropertiesRule has the ability to specify explicit
> attrname->propname mappings.


You *see* what happens when I'm not looking?  :-)  Thanks Simon.

Simon


Craig

Re: [Digester] Converting String value of an attribute to array of integers

[Simon Kitching <sk...@apache.org>]

On Fri, 2006-02-17 at 18:12 -0800, Craig McClanahan wrote:
> > <C ID="7" author="CT" depends="4,6">
> >         <flavour>AAC</range>
> > </C>
> >
> > I currently use d.addSetProperties("List/A") to read in my other
> > attributes.
> 
> 
> As you might have figured out, you are going to need a new Rule
> implementation to accomplish this.  Something along these lines should do
> the trick (where MyClass is the bean class):
> 

[snip]

I agree with Craig's suggestion here; a custom rule will do the trick
nicely. It might also be possible to register a custom String->int[]
converter for beanutils, but I have some vague memory that there's a
problem with that.

> Note that the above code assumes you change the attribute name from
> "depends" to "dependsValue".  Alternatively, you could leave the attribute
> name the same but change the property name on the bean to something else.
> Making the names different is important to avoid having the Set Properties
> Rule blow up because it doesn't know how to do this conversion.

Actually, SetPropertiesRule has the ability to specify explicit
attrname->propname mappings. Mapping to a null property causes the
attribute to be ignored. As you only need to override one particular
attribute you should be able to do:
  d.addSetProperties("List/C", "depends", null);
to map all attributes to identically named properties *except* the
depends property which will be ignored (and processed by your custom
rule instead).

Cheers,

Simon


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Re: [Digester] Converting String value of an attribute to array of integers

[Craig McClanahan <cr...@apache.org>]

 2/17/06, Siddharth Mathur <sm...@nellymoser.com> wrote:
>
> Dear all,
>
> I am trying to use Digester to read my own XML format (shown below) and
> convert it to correctly initialized objects.
>
> <List>
>
> <A ID="1" author="Home made">
>         <range>90</range>
> </A>
>
> <B ID="2" author="Apple Inc." depends="1">
>         <bitrate>90</range>
> </B>
>
> [...more entries here]
>
> <C ID="7" author="CT" depends="4,6">
>         <flavour>AAC</range>
> </C>
>
> </List>
>
>
> Classes A, B, C are all derived from a parent class which has three
> properties:
> i) ID (integer)
> ii) author (String)
> iii) depends (array of IDs i.e integers)
>
> Digester makes it very easy to create setter and getter methods and read
> in
> (i) and (ii) above. But how do I modify the default Rule so that the
> String
> value of the "depends" attribute is converted to an array of integers
> property? I will be happy to reformat the depends="4,6" part if required.
>
> I currently use d.addSetProperties("List/A") to read in my other
> attributes.


As you might have figured out, you are going to need a new Rule
implementation to accomplish this.  Something along these lines should do
the trick (where MyClass is the bean class):

    public class DependsRule extends Rule {

        public DependsRule(Digester digester) {
            super(digester);
        }

        public void begin(String namespace, String name, Attributes
attributes) {
            // Peek at the object at the top of the stack
            MyClass bean = (MyClass) digester.peek();
            int depends[] = parse(attributes.getValue("dependsValue"); //
See note below
            bean.setDepends(depends);
        }

        private int[] parse(String value) {
            // Parse the incoming string into an array of int
            // and return it ...
        }

    }

Note that the above code assumes you change the attribute name from
"depends" to "dependsValue".  Alternatively, you could leave the attribute
name the same but change the property name on the bean to something else.
Making the names different is important to avoid having the Set Properties
Rule blow up because it doesn't know how to do this conversion.

To register this rule on your digester instance, you'd say:

    digester.addRule(new DependsRule(digester));


Thank you for your time and patience,
> Siddharth


Craig