Thanks for replying. It will work in my use case.
On Tue, Jun 13, 2023 at 7:14 PM Christopher Schultz <
ch...@christopherschultz.net> wrote:
> Debraj,
>
> On 6/13/23 05:38, Debraj Manna wrote:
> > Can someone let me know how I can verify a velocity context against a
> > template? Basically, I want to throw some error if all variables are not
> > substituted in the velocity template.
> >
> > For example, let's say I have a velocity template, card.vm
> >
> > card {
> > type: CREDIT
> > company: VISA
> > name: "${firstName} ${lastName}"
> > }
> >
> > The substitution is done like below
> >
> > VelocityEngine velocityEngine = new VelocityEngine();
> > velocityEngine.init();
> >
> > Template t = velocityEngine.getTemplate("card.vm");
> >
> > VelocityContext context = new VelocityContext();
> > context.put("firstName", "tuk");
> > StringWriter writer = new StringWriter();
> > t.merge( context, writer );
> >
> > In this case, I want to throw some error specifying that lastName is not
> > replaced in template.
> >
> > Does velocity provide anything for this?
>
> No, but it would be easy to do. Instead of using the basic
> VelocityContext, wrap it in a custom one, something like this:
>
> public class WarningVelocityContext
> extends VelocityContext
> {
> public Object get(String key) {
> Object o = super.get(key);
>
> if(null == o) {
> throw new IllegalStateException("Key {" + key + "} has not
> been set");
> }
> }
> }
>
> Then in your code, wrap the context right before merging:
>
> t.merge(new WarningVelocityContext(context), writer);
>
> Note that this will throw exceptions for *anything* that's not found for
> any reason. If you try something like:
>
> $someObject.method()
>
> And "someObject" is null, then you'll get an error. It may be difficult
> to tell the difference between the things you "care about" and the
> things you do not. If you have a simple use-case, then probably this
> will work.
>
> -chris
>
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