velocity template drop element from array

Question

I'm trying to get the last element of an array in a velocity template dropped before joining it together into a string and showing the result in the "className": key below:

    #set($elem = '"System.NotImplementedException: Test Exception')
    #set($trace = $elem.replace('"',""))
    #set($tracearray = $trace.split("\."))
    #set($arraysize = $tracearray.size())
    #set($lastelem = $tracearray.size() - 1)
    {
      "className":$tracearray.remove($lastelem).toString(),
      "method":"$tracearray[$lastelem]"
    }#if($foreach.hasNext),#end
    #end
  ]

I've tried several different ways to get the array to drop the element and join it together into a string but haven't had any luck so far.

From the above example I'm looking for the following output to be achieved.

{
  "className":"System",
  "method":"NotImplementedException: Test Exception"
}

The $elem variable will be holding strings of various lengths and with a different number of .'s in them to split on so the lengths of the arrays will vary.

score 1 · Accepted Answer · answered Feb 22 '17 at 19:23

If you only need to remove the last element, why bother splitting the whole string? You could just do some parsing to extract the class name:

#set($elem = '"System.NotImplementedException: Test Exception')                                                                                                                                                 
#set($trace = $elem.replace('"',""))
#set($dot = $trace.lastIndexOf('.'))
#set($className = $trace.substring(0, $dot))
#set($method = $trace.substring($dot + 1))
{
  "className": "$className",
  "method": "$method"
}

Or, to accomodate the fact that the message at the end could contain a dot:

#set($elem = '"System.NotImplementedException: Test Exception')                                                                                                                                                 
#set($trace = $elem.replace('"',""))
#set($colon = $trace.indexOf(':'))
#set($dot = $trace.lastIndexOf('.', $colon))
#set($className = $trace.substring(0, $dot))
#set($method = $trace.substring($dot + 1))
{
  "className": "$className",
  "method": "$method"
}

With the method you have chosen, you would need another tool to join back the array elements with '.'. All this said, if you happen to be able to populate your Velocity context with a custom tool, all this stuff would be more easily done from with this custom tool.

thanks Claude, this worked for me. I'm not able to do anything outside of the velocity template, unfortunately, because this is being done through AWS API Gateway so I'm limited to doing all data manipulation from within the template itself. — PurrBiscuit, Feb 23 '17 at 16:51

velocity template drop element from array

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