Dynamically change the class attribute of jasper's textFieldExpression

I have to display a textField a jasper report. The report is generated to an Excel file. The problem is with a particular column which sometimes has a string and sometimes has an integer (开发者_开发问答also as string). When it has an integer as string, Excel complains that there is a number stored as text in that particular cell. I would like to display the number as a number, not as a string.

How can I dynamically change the class attribute of the textFieldExpression to be java.lang.Integer when the string is a valid number? Or is another other way to insert a condition?

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Use two fields and a PrintWhenExpression that will determine the appropriate field to display.