It depends on what you mean by velocity tools. As the description on http://velocity.apache.org/tools/releases/2.0/ says, a tool is just a Plain Old Java Object, so any Java object can act as a tool.
Officially, a "tool" is something that can be automatically placed in the context when you have a more complex/automatic Velocity Engine setup, like VelocityViewServlet or VelocityStruts, or using one of the configuration mechanisms listed on http://velocity.apache.org/tools/devel/config.html Unofficially, if you're working directly with the engine, you can place any object in the VelocityContext when rendering a parsed template. So, there's no restriction on the class that you're using as a tool, other than: - only public methods can be invoked from Velocity, but there can be helper private methods if they help you organize the code - if the tool is automatically instantiated, it must have a public constructor with no parameters; if you instantiate it manually, you can pass as many arguments as you want in the constructor On 08/08/2013 12:06 PM, O. Olson 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. > > --------------------------------------------------------------------- > To unsubscribe, e-mail: user-unsubscr...@velocity.apache.org > For additional commands, e-mail: user-h...@velocity.apache.org > -- Sergiu Dumitriu http://purl.org/net/sergiu --------------------------------------------------------------------- To unsubscribe, e-mail: user-unsubscr...@velocity.apache.org For additional commands, e-mail: user-h...@velocity.apache.org
