can Velocity set a default value for a variable when no value found in VelocityContext?

Question

Velocity just print the tag name if no value was found in VelocityContext, ie, $name in my template file, but there is no value for "name" in VelocityContext, so just "$name" was printed. I want Velocity to print a default value if there is no value for the variable, I just tried to extends AbstractCotnext and override internalGet() method, but the return value of internalGet() will be cast to Node object, I don't know how to create a new Node object in my internalGet() method, and also I think this way is very complex.

is there a simple way to set a default value (default value is just a string) ?

thanks.

score 20 · Answer 1 · answered Dec 14 '12 at 11:50

20

Not easily for all variables as far as I see, I only managed to do it for some variables specifically as follows:

Template:

#if ( !$somevar )
#set ( $somevar = "mycontent" )
#end

Var is: $somevar

Result:

Var is: mycontent

answered Dec 14 '12 at 11:50

centic

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If you are a Marketo user/campaigner, the above mentioned script will not work. There should be probably other Veolocity syntax and only following will be correct: `#if ( $somevar == "" ) #set ( $somevar = "mycontent" ) #end Var is: $somevar ` – Piotr Kowalski Nov 13 '19 at 14:25

Will C. · Answer 2 · 2013-04-15T23:23:46.650

9

Create a velocimacro in your template:

#macro(defaultValue $parm)  
#if (!$!parm || $!parm == "")  
i-like-will
#else  
$parm  
#end  
#end

And call it like this in the same template:

#defaultValue($name)

Check Apache Velocity - Velocity User Guide for more info on velocimacros (and velocity in general).

edited Apr 15 '13 at 23:23

answered Dec 16 '12 at 05:05

Will C.

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why do you have \ symbols in front of your #s ? I thought macros and if statements were defined as #macro and #if not \#if – Andy Dingfelder Apr 03 '13 at 21:45
You are correct, I'm not sure how the formatting got all messed up. I've fixed it. – Will C. Apr 15 '13 at 23:24
Thanks, I thought it had some special meaning I had missed :-) – Andy Dingfelder Apr 18 '13 at 02:53

score 3 · Answer 3 · answered Jun 29 '15 at 17:44

A little late to the party, but you could also perform a check when defining a variable. I had to compress this to one line to remove excess space in the output, but here is an example from one of my projects:

#set ( $qlDefault = "qlinks" )
#set ( $qlClass = "#if($sharedCtaImage.getChild('path').value != '/')$qlDefault#else$qlDefault full#end" )

Default class is defined, then I check if another, specific value is filled in to determine if I keep the default class or append an additional class. This could also work for swapping out classes as well.

score 2 · Answer 4 · answered Dec 14 '12 at 16:44

2

Google around for Velocity ReferenceInsertionEventHandler for a way to do it broadly.

Consider the DisplayTool's alt() method for individual cases (part of the VelocityTools project)

answered Dec 14 '12 at 16:44

Nathan Bubna

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thanks every body every much, and allow me to ask another question: is there a way to change the variable name before render the output? for example, the variable name is userName in template file, but in VelocityContext, the key is USERNAME, I want to change variable name to capital word before render. – hiway Dec 16 '12 at 15:09

score 1 · Answer 5 · answered Feb 07 '18 at 06:34

1

For an empty default value, $!name will do. Otherwise,

#{if}($name)${name}#{else}${default_value}#{end}

See http://velocity.apache.org/engine/2.0/user-guide.html#quiet-reference-notation

answered Feb 07 '18 at 06:34

Frank R.

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score -1 · Answer 6 · edited May 23 '17 at 12:25

-1

There are a couple things you can do short of hacking Velocity internals. Have a look at this question.

edited May 23 '17 at 12:25

Community

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answered Dec 14 '12 at 15:03

Evan Haas

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can Velocity set a default value for a variable when no value found in VelocityContext?

6 Answers6

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