an exception problem!!!

[khabot zakaria]

Hi,
I have this exception message and don't know the source of the problem :
500 Internal Server Error
javax.servlet.jsp.JspException: Exception creating bean of class mypackage5.Book: {1}
        void org.apache.struts.taglib.html.FormTag.initFormBean()
                FormTag.java:563
        int org.apache.struts.taglib.html.FormTag.doStartTag()
                FormTag.java:520
        void _BookView._jspService(javax.servlet.http.HttpServletRequest, 
javax.servlet.http.HttpServletResponse)
        [/BookView.jsp]

can someone help me.
thanks.
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