Forum Discussion

Charles's avatar
Charles
New Contributor II
4 years ago
Solved

Null Safe access option for object value reference in JSON Generator snap?

Hi, I’m trying to reference a value from the input object in the JSON Generator snap. The property is optional in the upstream snaps. If I straight reference it, I’ll get an “Invalid JSON-Path fiel...
json
  • del's avatar
    del
    4 years ago

    @Charles,
    Like Patrick, I was also thinking Velocity (VTL) as a solution, but as I tried to solution your original post, the Workday namespace convention in the property names adds some complexity. I don’t know if Velocity beats the null-safe mapper for your particular use case, but it can be good info for your tool belt in the future.

    The kind of ugly solution I came up with (in a one-liner) is:

    [
    {
       "output" : #set ($pd = $['wd:Project_Data']) #set ($ed = $pd['wd:End_Date']) #if (${ed}) ${ed} #else null #end
    }
]

    I’m not well versed in VTL, so there’s likely something a little cleaner than the above.

ptaylor's avatar
ptaylor
Employee
4 years ago

@Charles Please note the following documentation at the top of the default template in the JSON Generator:

Enter your JSON-encoded data in this space. Note that this text is
treated as an Apache Velocity template, so you can substitute values
from input documents or the pipeline parameters. See the following
URL for more information about Velocity:
https://velocity.apache.org/engine/devel/user-guide.html

This means you can use Velocity syntax, not SnapLogic EL syntax, in your templates, like this:

[
    {
        "result" :
#if($msg)
        ${msg}
#else
        ${fallback}
#end
    }
]

Here’s a pipeline to demonstrate this:
Velocity Null Check_2021_12_07.slp (4.8 KB)

You can do the same on a single line like this:

        "result" : #if($msg) $msg #else $fallback #end
Charles's avatar
Charles
New Contributor II
4 years ago

Got it. That makes sense. Thank you for the explanation and syntax example!