Re: Documentation regarding Custom Utility Class for Velocity

If you are putting the MyUtil class into the context yourself (as your
code seems to suggest, then it is up to you whether you want to create
a single static instance or a new instance for each request.  This is
out of Velocity's control as you describe things.

If you'd like tool instantiation to be managed for you, you may use
the VelocityTools library, either the VelocityView or even just the
GenericTools support. I can go into this further if the documentation
and examples aren't clear.

Bean syntax is optional for methods. You can always call methods with
the full name if you like: $myUtil.getNumRows()

Velocity does not (by default) expose fields, even public final
constant ones.  This is documented thoroughly.  You can adapt the
object to expose fields:
http://velocity.apache.org/engine/releases/velocity-1.7/apidocs/org/apache/velocity/app/FieldMethodizer.html
or Velocity itself:
http://maven-doccheck.sourceforge.net/samples/ShinobuDemo/apidocs/org/apache/velocity/tools/generic/introspection/PublicFieldUberspect.html

On Thu, Aug 8, 2013 at 9:06 AM, O. Olson <[email protected]> wrote:
> Hi,
>
>     I am wondering if there is any documentation on writing your own Utility Class or Custom Tool to add to Velocity. The only place I found some help is http://www.sergiy.ca/how-to-create-custom-tools-for-apache-velocity/  (There is something regarding Custom Tools at http://velocity.apache.org/tools/releases/2.0/creatingtools.html   - but I could not find anything regarding  Utility Classes that we can push into the Velocity Context.)
>
>     Originally, I was thinking of doing my processing/customization in Velocimacros, but that is turning out to be a bit more complex/cumbersome than I expected. I am thinking of doing this in Java, and pushing the results to the Velocity Context as a single object/utility class instance. For purposes of discussion let us assume, I do something like the following in Java:
>     VelocityContext context;
>     context.put("myUtil", new MyUtil());
>
>     I'd appreciate if I could get answers/ideas on:
>
> 1.    I am wondering if MyUtil() needs to be static across requests.  I intend MyUtil() to provide easy access and manipulation of the current request. Hence, I would probably do something like the following in Java:
>
> context.put("myUtil", new MyUtil(currentWebRequest));
>
>     i.e. I would instantiate MyUtil with the current Web Request. MyUtil could then provide easy access to say the Number of Rows in the Request. So in the Template I could do:
>
>     $myUtil.NumRows
>
> If MyUtil() is static, this would not work, because different requests would have different number of Rows. Should the Utility Class/Object be static? The example mentioned above shows only static methods, hence my question.
>
> 2.    Should my Utility class follow the bean syntax i.e. for the above example of  $myUtil.NumRows in the template, would I need to declare something like the following in the MyUtil Java class:
>
> public int getNumRows() { }
>
> 3.    What would be a good way to pass a Constant from Java to the Template? Should I use the bean syntax again? E.g. in the template
> $myUtil.JAVA_CONSTANT
>
>     Would I need to have something like:
> public int getJAVA_CONSTANT () { }
>
> Thank you in advance for your help,
> O. O.
>
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