Grails sort params

I am using ExtJS4 library to show a grid of paged data served by a Grails controller and returned开发者_运维技巧 as JSON. One of the fields is a calculated field that I cannot pass back to the database for a query ... because it's calculated. What is a good solution to implement for this type of column sort request? Other columns I just pass back to the query through : list(params)

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if you have a list, you can use this.

   def a = [5,3,4,2,1]
    //for asc
     a.sort{+it}
    //for des
     a.sort{-it}