How to define Custom Exception in Web Application(Struts2, Hibernate,Spring)?

Question

Hi,

This is a very general question, I hope you won't laugh or scold me.Anyway here it comes:

I am using struts2, hibernate, jpa and spring.I have four layers in my application:
1.Struts Action Layer,
2.Business Layer,
3.Service Layer,
4.Common Utility Layer
So I need to define a Custom Exceptions so that if exception happens at server layer which is database layer it will go to the business layer and then business layer will throw a new exception and this exception with go to the Struts Action layer.From there I will throw the MainApplicationException and then I will show to the end user some meaningful information instead of null pointer exception.

I have defined a custom exception shown below:

 public class MainApplicationException extends Exception{



    private static final long serialVersionUID = 1L;

    /**
     * @param ErrMsg: error message.
     */
    public MainApplicationException(String ErrMsg) {
        super(ErrMsg);
    }



}

The MainApplicationException is the root exception.After that all the above mentioned exception happens.
Please suggest me how should I proceed. If possible put some some code.

Thanks in advance.