Re: problem parsing references in Velocity

[Christopher Schultz]

Andy,

andyandy wrote:

I need to send some data to an external service that interacts with my
application. It's just a group of ids and values that the service needs. The
real code that I have is:

#set
($query="id_maq=escape($!{idMaq})&referer=escape($!{referer})&urlv=escape($!{urlv})&urlf=escape($!{idMaq}$!{url})&serv=escape($!{serv})")

The problem is that when any of the variables is null it tries to
"escape(null)", which I don't want. I only want to escape the values that I
do have.

You can do this in many ways.

1. Use iterative conditionals

  #if($idMaq)
    #set($query = "$query&id_maq=${idMaq})
  #end
  #if($referer)
    #set($query = "${query}&referer=${referer})
  #end
  .
  .
  .

2. Write a macro to do the conditionals for you:

  #macro(possiblyEscape $paramName $paramValue)
  #if($paramValue)&${paramName}=${paramValue}
  #end

  (note that you might want to put this all on one line to avoid
  excess whitespace)



I'm sure there are other options.



-chris

($query = "#possiblyEscape('id_maq', $idMaq)#possiblyEscape('referer', $referer) ... ") Also note that you might want to run your parameter names and values through URLEncoder.encode. Consider using LinkTool from Velocity Tools, which handles lots of stuff for you like this.

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