[NoClassDefFoundError and ClassNotFoundException are raised at runtime.]

Eclipse4.16
JDK8
JasperReport 6.20.0
In the above environment, I have created a JasperReport class in an existing project.
The application will be J2EE.
I have placed the library in the lib folder and created it so that the library is also included in the ear file through the classpath.
Ant builds successfully, but I get NoClassDefFoundError and ClassNotFoundException at runtime.

    java.lang.NoClassDefFoundError: net.sf.jasperreports.engine.JRDataSource
    ・・・・
    Caused by: 
    java.lang.ClassNotFoundException: net.sf.jasperreports.engine.JRDataSource

The library placed in lib is as follows

    jasperreports-6.20.0.jar
    jasperreports-castor-6.20.0.jar
    jasperreports-chart-customizers-6.20.0.jar
    jasperreports-chart-themes-6.20.0.jar
    jasperreports-fonts-6.20.0.jar
    jasperreports-functions-6.20.0.jar
    jasperreports-metadata-6.20.0.jar

I don't know what is causing this.
Please let me know how to deal with it.