Custom Functions for DIH

It is possible to plug in custom functions into DIH. Implement an Evaluator and specify it in the data-config.xml . Following is an example of an evaluator which does a 'toLowerCase' on a String.

<dataConfig>
   <function name="toLowerCase" class="foo.LowerCaseFunctionEvaluator"/>
   <document>
   <entity query="select * from table where name='${dih.functions.toLowerCase(dih.request.user)'">
    <!- ......field declarations......->
   </entity>
</dataConfig>

The implementation of LowerCaseFunctionEvaluator

  public class LowerCaseFunctionEvaluator extends Evaluator{
    public String evaluate(String expression, Context context) {
      List l = EvaluatorBag.parseParams(expression, context.getVariableResolver());

      if (l.size() != 1) {
          throw new RuntimeException("'toLowerCase' must have only one parameter ");
      }
      return l.get(0).toString().toLowerCase();

    }

  }