code: protected static JRDesignExpression getExpressionFromVariable(JRDesignVariable var){
  		JRDesignExpression exp = new JRDesignExpression();
  		exp.setText("$V{" + var.getName() + "}");
  		exp.setValueClass(var.getValueClass());
  		return exp;
  	}
docs: Generates an expression from a variable
  @param var The variable from which to generate the expression
  @return A expression that represents the given variable