Macros to convert Plain Old Java Objects in Velocity templates to JSON

POJOToJSON.mv

#macro(POJOListToJSON $list )
	#set($myList = $list )
	{
	#foreach($key in $myList.keySet())
		#set($x = $myList.get($key))
		"$key": #POJOToJSON($x) ##
		#if($velocityCount != $myList.keySet().size())
		,
		#end
	#end
	}
#end

#macro(POJOArrayToJSON $arr)
	#set($myArr = $arr)
	[
	#foreach($x in $myArr)
		#POJOToJSON($x) ##
		#if($velocityCount != $myArr.size())
		,
		#end
	#end
	]
#end

## try some common POJO Patterns
#macro(POJOPatternToJSON $item)
  #set($match = false)
  #if($item.name)
    #set($match = true)
    #set($name = $item.name)
    #if($item.value)
      #set($value = $item.value)
    #end
    #set($obj = {
      "$item.name" : $item.value
    })
    #POJOToJSON($obj) ##
  #end
  #if($item.items)
    #set($match = true)
    #set($items = $item.items)
    #POJOToJSON($items) ##
  #end
  #if(!$match)
    ##/* unknown POJO pattern for $item */
    null
  #end
#end

#macro(POJOToJSON $item)
  $response.setContentType("application/json")
  ## standard JSON types
	#if($item.keySet())
	#POJOListToJSON($item)
	#elseif($item.size())
	#POJOArrayToJSON($item)
	#elseif($item == true || $item == false)
    $item
	#elseif(!$item)
	  null
	#elseif($item.length() == 0)
		""
	#elseif($item.length() && $item.matches("\d+"))
		$item
	#elseif($item.length())
    "$item"
	## try common POJO Patterns
	#else
	#POJOPatternToJSON($item)
	#end
#end