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Macro body is evaluated as Velocity Template! This allows you to use #if #end constructions around JSON mapping parts.

Field values are stored in Velocity templates under field names!

For multi-value holding fields and for the single choice fields, like dropdowns, radio group fields, etc the field is always present in the context and has the value, so you cannot check it with 

Code Block
#if(${somefield})
#end

as it will always be evaluated to true, but you can check if it has any values

Code Block
--- check if field has no values

#if(${somefield.isEmpty()})
#end


--- check if the field is NOT empty and has values

#if(!${somefield.isEmpty()})
#end



Also, there is standard set of objects inside the context


context.put("entry", entry); <- ConfiForms Entry (raw)
context.put("user", user); <- Confluence user object
context.put("page", contentObject); <- AbstractPage object

From ConfiForms version 1.49.3 there are additional objects in the context:

context.put("generalUtil", newcom.atlassian.confluence.util.GeneralUtil());
context.put("res", ServletActionContext.getResponse());
context.put("req", ServletActionContext.getRequest());
context.put("action", com.atlassian.confluence.renderer.radeox.macros.MacroUtils.getConfluenceActionSupport());

Very similar to what is available in the context when you develop Confluence user macros: 
https://confluence.atlassian.com/doc/writing-user-macros-4485.html
https://developer.atlassian.com/server/confluence/confluence-objects-accessible-from-velocity/                
              
which you can reference as any other variable in Velocity using velocity syntax, for example: ${page.id} to reference page id of current page

Also, a helpful link from apache 
---- copied from Apache https://wiki.apache.org/velocity/CheckingForNull

Q: I want to check for null, something like this:

#if ($car.fuel == null)

A: There are several approaches. Select the one most suitable depending on what you really want to do. (Thanks, everybody, for all the feedback on the user list.) See also: Bugzilla #20999Bugzilla #27741VelocityNullSupport.

Approach 1: Use the fact that null is evaluated as a false conditional. (cf. http://velocity.apache.org/engine/devel/user-guide.html#Conditionals)

#if( ! $car.fuel )
  • Note: The conditional will also pass if the result of $car.fuel is the boolean false. What this approach is actually checking is whether the reference is null or false.

Approach 2: Use the fact that null is evaluated as an empty string in quiet references. (cf. http://velocity.apache.org/engine/devel/user-guide.html#quietreferencenotation)

#if( "$!car.fuel" == "" )
  • Note: The conditional will also pass if the result of $car.fuel is an empty String. What this approach is actually checking is whether the reference is null or empty.

BTW, just checking for empty can be achieved by:

#if( "$car.fuel" == "" )

Approach 3: Combine Approach 1 and 2. This will check for null and null only.

#if ((! $car.fuel) && ("$!car.fuel" == ""))
  • Note: The logic underlying here is that: "(null or false) and (null or > empty-string)" => if true, must be null. This is true because "false and empty-string and not null" is never true. IMHO, this makes the template too complicated to read.

Approach 4: Use a Tool that can check for null (NullTool,ViewNullTool).

#if( $null.isNull($car.fuel) )
  • Note: Of course, NullTool must must be in the Context as $null in this case (in ConfiForms it is included into the context under "null" variable name).

Info

In ConfiForms version 2.15.3+ we have extended NullTool to have 2 more convenient methods (isNullOrEmpty and isNotNullOrEmpty) to check if the value is null or empty


isNull
isNullOrEmpty
isNotNull
isNotNullOrEmpty


Approach 5: Don't check for null directly, use a self-explaining method.

#if( $car.fuelEmpty )
  • Note: This is my (Shinobu Kawai's) recommended solution. You have to implement the method, but it makes the template so easy-to-read.


public boolean isFuelEmpty()
{
  // return true if fuel is empty.
}

Approach 6: Use a custom directive. cf. IfNullDirectiveIfNotNullDirective

#ifnull( $car.fuel )
#ifnotnull( $car.fuel )
  • Note: You will have to register the directive in your velocity.properties.


userdirective = org.apache.velocity.tools.generic.directive.Ifnull
userdirective = org.apache.velocity.tools.generic.directive.Ifnotnull

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