[how to fix this problem? please help me.]

I managed to fix this problem. It's a problem to do with JasperSoft Studio version.

In my case I use Netbeans and JasperSoft Studio 6.11.0

I was getting an identical problem to what you posted, so I expect solution could be the same.

In my netbeans project POM  I was using

net.sf.jasperreports Version 6.9.0,

Updating this to Version 6.11.0 solved my problem

Hope this solves your problem.

[how to fix this problem? please help me.]

Hello, have you gotten any solution? I got a similar challenge too. Same error. Tried also the suggestion here unsuccessfully.